Electrical Installations in Hazardous (Classified) Locations
Initial publication
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in Electrical Installations in Hazardous (Classified) Locations.
+---
+title: Electrical Installations in Hazardous (Classified) Locations
+category: Electrical
+description: >
+ When to use: The electrical installation inside, and at the boundary of, every location classified under NFPA 70 Articles 500 through 516 on a water, wastewater, industrial, institutional, or commercial project: the area classification as a contract deliverable and the basis documents behind it (NFPA 497, NFPA 499, NFPA 820, NFPA 30, NFPA 30A, NFPA 58, API RP 500 and RP 505), the choice between the Division and Zone systems, the protection techniques of NFPA 70 500.7 as the menu per kind of equipment (explosionproof and dust-ignitionproof enclosures, purged and pressurized enclosures under NFPA 496, intrinsically safe systems under Article 504, nonincendive equipment and circuits, oil immersion, hermetic sealing, and combustible gas detection as a technique), the wiring methods permitted by class and division, conduit and cable seals and drainage, bonding within the classified location, the listing and marking every item of equipment must carry and its verification against the classification drawings, the specific-occupancy articles, and the classified-location inspection before energization and the record of classified areas delivered at closeout. Written for the wet wells, headworks, digester and gas handling areas, sludge galleries, chemical rooms, and fuel areas of treatment plants and pump stations, and equally for a fuel dispensing island, a paint booth, or a dust-handling process.
+ Not intended for: Unclassified areas, which [[sync/raceways-and-conduit]], [[sync/cable-tray]] and [[sync/underground-ductbank]] cover; building wire and cable ([[sync/conductors-and-cables]]); the cable of an intrinsically safe circuit, its jacket color and its entity parameters ([[sync/instrumentation-and-control-cable]]); the grounding electrode system and the equipment grounding conductors ([[sync/grounding-and-bonding]]); the equipment products installed in the location, each of which carries its own hazardous-location enclosure and listing under its own standard ([[sync/electric-motors]], [[sync/combination-motor-starters]], [[sync/analytical-instrumentation]], [[sync/level-sensors]], [[sync/flow-measurement]], [[sync/pressure-instrumentation]], [[sync/temperature-instrumentation]], [[sync/control-valves-and-actuators]], [[sync/electric-heat-tracing]], [[sync/overhead-material-handling]], [[sync/dust-and-fume-collection]], [[sync/submersible-solids-handling-pumps]], [[sync/packaged-pump-stations]]); the gas detection equipment itself ([[sync/gas-detection-systems]]); the industrial control panel that houses the intrinsically safe barriers outside the location ([[sync/industrial-control-panels]]); the ventilation on which an NFPA 820 classification depends, which is mechanical scope; the fire protection, construction and separation requirements of NFPA 820 beyond the electrical classification; the facility electrical safety program ([[sync/electrical-safety-program]]); and the label materials and methods on equipment in classified locations ([[sync/equipment-labeling]]).
+---
+
+# Scope {toc}
+
+## This standard governs the electrical installation inside every hazardous (classified) location on the project and at each boundary where a raceway or cable leaves one: how the location is classified and recorded, which protection technique each kind of equipment in it uses, how the wiring is run, sealed and bonded, how the listing and marking of every item of equipment is verified against the classification, and how the installation is inspected before it is energized. {note}
+
+## The classification of a location is the Engineer of Record's determination and a contract document, and this standard is read against it: it does not tell the reader whether a space is classified, it tells the Contractor what an installation inside a space the drawings have classified must be. {note}
+
+## A classified location in a treatment plant or pump station is an ordinary room with an extraordinary consequence: a wet well, a screenings room, a digester gallery, a gas compressor room or a chemical feed room contains, or can contain, a flammable atmosphere, and an arc at an ordinary junction box, a spark at a motor terminal, or a hot surface on an unmarked enclosure is an ignition source in it. The installation requirements of NFPA 70 Chapter 5 exist to keep every such source either contained, de-energized, or below ignition energy, and they are the ones most often left out of a plant specification because the general electrical sections assume an unclassified building. {note}
+
+## The following are governed elsewhere and are outside this standard. {note}
+
+- Raceway, conduit, boxes, supports and fill outside classified locations, and the general raceway rules this standard adds to within them ([[sync/raceways-and-conduit]]); cable tray outside classified locations ([[sync/cable-tray]]); concrete-encased duct banks and their structures ([[sync/underground-ductbank]])
+- Building wire, cable, terminations and conductor identification ([[sync/conductors-and-cables]])
+- The cable of an intrinsically safe circuit, its published inductance and capacitance, the entity-parameter sum on the cable schedule, and the light blue jacket ([[sync/instrumentation-and-control-cable]])
+- The grounding electrode system, the equipment grounding conductors, and the bonding of the electrical system as a whole ([[sync/grounding-and-bonding]])
+- The motor, starter, instrument, actuator, luminaire, crane, dust collector, heat-tracing circuit, pump, and packaged station installed in the location, each with the enclosure and listing its own standard specifies for the location
+- The gas detectors, their controllers, calibration, and alarm functions ([[sync/gas-detection-systems]])
+- The control panel outside the classified location that houses the intrinsically safe barriers or isolators ([[sync/industrial-control-panels]]) and the controller it serves ([[sync/programmable-logic-controllers]])
+- The ventilation that NFPA 820 ties a lower classification to, which is designed, furnished and controlled under the mechanical documents
+- The fire protection, construction, separation, and physical-protection requirements of NFPA 820 other than the electrical area classification
+- The facility electrical safety program, energized work permits, and lockout ([[sync/electrical-safety-program]])
+- Label materials, label construction, and the methods of attaching labels to enclosures in classified locations ([[sync/equipment-labeling]])
+
+## The class, division or zone, group, and extent of each classified location, and the material whose properties establish its classification, shall be as indicated on [[drawing: the hazardous area classification drawings]].
+
+## Every electrical installation within the extent so indicated, and every raceway and cable crossing its boundary, shall comply with this standard in addition to the standard that governs the same work in an unclassified location.
+
+# Referenced Standards {toc}
+
+## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
+
+## Where the contract documents, the adopted codes, the Authority Having Jurisdiction, or two referenced standards impose conflicting requirements, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+| Standard | Title |
+|----------|-------|
+| NFPA 70 | National Electrical Code (Articles 500 through 516) |
+| NFPA 496 | Standard for Purged and Pressurized Enclosures for Electrical Equipment |
+| NFPA 497 | Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas |
+| NFPA 499 | Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas |
+| NFPA 820 | Standard for Fire Protection in Wastewater Treatment and Collection Facilities |
+| NFPA 30 | Flammable and Combustible Liquids Code |
+| NFPA 30A | Code for Motor Fuel Dispensing Facilities and Repair Garages |
+| NFPA 58 | Liquefied Petroleum Gas Code |
+| NFPA 33 | Standard for Spray Application Using Flammable or Combustible Materials |
+| NFPA 409 | Standard on Aircraft Hangars |
+| API RP 500 | Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Division 1 and Division 2 |
+| API RP 505 | Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class I, Zone 0, Zone 1, and Zone 2 |
+| ANSI/ISA-60079-10-1 | Explosive Atmospheres – Part 10-1: Classification of Areas – Explosive Gas Atmospheres |
+| ANSI/ISA-RP12.06.01 | Recommended Practice for Wiring Methods for Hazardous (Classified) Locations Instrumentation, Part 1: Intrinsic Safety |
+| UL 1203 | Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations |
+| UL 913 | Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, and III, Division 1, Hazardous (Classified) Locations |
+| UL 121201 | Nonincendive Electrical Equipment for Use in Class I and II, Division 2 and Class III, Divisions 1 and 2 Hazardous (Classified) Locations |
+| UL 698A | Industrial Control Panels Relating to Hazardous (Classified) Locations |
+| UL 886 | Outlet Boxes and Fittings for Use in Hazardous (Classified) Locations |
+| UL 2225 | Cables and Cable-Fittings for Use in Hazardous (Classified) Locations |
+| ANSI/UL 60079-0 | Explosive Atmospheres – Part 0: Equipment – General Requirements |
+| UL 6 | Electrical Rigid Metal Conduit – Steel |
+| UL 6A | Electrical Rigid Metal Conduit – Aluminum, Red Brass, and Stainless Steel |
+| UL 1242 | Electrical Intermediate Metal Conduit – Steel |
+| NEMA RN 1 | Polyvinyl-Chloride (PVC) Externally Coated Galvanized Rigid Steel Conduit and Intermediate Metal Conduit |
+| NEMA 250 | Enclosures for Electrical Equipment (1000 Volts Maximum) |
+| UL 50E | Enclosures for Electrical Equipment, Environmental Considerations |
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### The Contractor shall submit the following before any raceway, cable, box, fitting, or sealing fitting is installed within a classified location:
+
+- Product data for every box, fitting, sealing fitting, drain and breather fitting, flexible fitting, cable gland and cable termination fitting to be installed within a classified location or at its boundary, stating the listing, the class, division or zone, and group it is listed for, and the thread form
+- Product data for the sealing compound and the fiber dam material, stating the listing with the sealing fittings on which it will be used, the minimum melting point, and the manufacturer's pouring instructions
+- A wiring method schedule listing each classified area shown on the classification drawings with the wiring method, the conduit construction, and the flexible connection method to be used in it
+- A seal schedule listing every sealing fitting to be installed, by raceway or cable number and location, the enclosure or boundary it serves, the fitting type and trade size, and whether it is a seal, a drain seal, or a cable seal
+- Product data and a sequence of operation for every purged and pressurized enclosure, stating the NFPA 496 type, the protective gas source, the purge flow and the exchange volume, the pressure or flow switch, and the alarm and shutdown logic
+- A listing schedule of every item of electrical equipment to be installed within each classified area, stating for each item the class, division or zone, group, temperature code, and ambient temperature range on its listing, cross-referenced to the classification of the area it is installed in
+- Where combustible gas detection is selected as a protection technique, the documentation NFPA 70 500.7(K) requires: the detection equipment and its listing for the gas present, the detector locations, the alarm and shutdown criteria, and the calibration frequency
+
+```datasheet
+label: Action Submittals Required
+type: checkbox
+options:
+ - "Product data for boxes, fittings, sealing fittings, flexible fittings and cable fittings"
+ - "Sealing compound and fiber dam product data"
+ - "Wiring method schedule by classified area"
+ - "Seal schedule"
+ - "Purged and pressurized enclosure data and sequence of operation"
+ - "Listing schedule of equipment in each classified area"
+ - "Combustible gas detection protection technique documentation"
+default:
+ - "Product data for boxes, fittings, sealing fittings, flexible fittings and cable fittings"
+ - "Sealing compound and fiber dam product data"
+ - "Wiring method schedule by classified area"
+ - "Seal schedule"
+ - "Listing schedule of equipment in each classified area"
+constraint: all_of
+```
+
+## Intrinsically Safe System Submittals {toc}
+
+### Where an intrinsically safe circuit enters a classified location, the Contractor shall submit the following before the circuit is installed:
+
+- The control drawing for each intrinsically safe loop, as the listing of the barrier or isolator and of the field device requires under NFPA 70 504.10(A), showing every device in the loop
+- The entity-parameter verification for each loop, showing that the field device parameters and the cable inductance and capacitance over the installed length, stated under [[sync/instrumentation-and-control-cable]], are within the parameters of the barrier or isolator
+- Product data for each barrier or isolator with its listing and its control drawing number
+- A detail of the intrinsically safe ground bus, its insulation from the enclosure, and its conductor to the grounding electrode system
+- A schedule of every intrinsically safe circuit with its loop number, its barrier, the field device, the raceway or cable it is run in, and the enclosures it passes through
+
+```datasheet
+label: Intrinsically Safe System Submittals Required
+type: checkbox
+options:
+ - "Control drawing for each intrinsically safe loop"
+ - "Entity-parameter verification for each loop"
+ - "Barrier and isolator product data"
+ - "Intrinsically safe ground bus detail"
+ - "Intrinsically safe circuit schedule"
+default:
+ - "Control drawing for each intrinsically safe loop"
+ - "Entity-parameter verification for each loop"
+ - "Barrier and isolator product data"
+ - "Intrinsically safe ground bus detail"
+ - "Intrinsically safe circuit schedule"
+constraint: all_of
+```
+
+## Closeout Submittals {toc}
+
+### At substantial completion, before final acceptance, the Contractor shall submit the following:
+
+- The record of classified areas in the format indicated under the Record of Classified Areas article, reflecting every change to a source, a boundary, or a ventilation dependency made during construction
+- The completed seal schedule, with the pour date and the installer of every seal
+- The classified-location inspection report, signed by the inspecting party indicated in the datasheet, with every deficiency found and its correction
+- The commissioning report for each purged and pressurized enclosure, recording the purge duration, the pressure held, and the proof of the alarm and shutdown functions
+- The as-installed verification of each intrinsically safe loop against its control drawing
+- The listing schedule of equipment in each classified area, corrected to the equipment installed
+
+```datasheet
+label: Closeout Submittals Required
+type: checkbox
+options:
+ - "Record of classified areas"
+ - "Completed seal schedule with pour dates"
+ - "Classified-location inspection report"
+ - "Purged and pressurized enclosure commissioning report"
+ - "As-installed intrinsically safe loop verification"
+ - "Corrected listing schedule of equipment in each classified area"
+default:
+ - "Record of classified areas"
+ - "Completed seal schedule with pour dates"
+ - "Classified-location inspection report"
+ - "Corrected listing schedule of equipment in each classified area"
+constraint: all_of
+```
+
+# Quality Assurance {toc}
+
+## Installer Qualifications {toc}
+
+### Work within a classified location shall be performed by licensed electricians employed by a licensed electrical contractor, under a foreman who has installed explosionproof raceway systems and poured conduit seals on at least two prior projects of comparable classification.
+
+### Where the parties disagree whether the foreman's prior projects are of comparable classification, the Engineer of Record shall make the initial determination.
+
+### Where the Zone system is selected in the datasheet, the installation and its inspection shall be performed by persons qualified in the Zone system, as NFPA 70 505.7(A) requires.
+
+## Listing and Labeling {toc}
+
+### Every box, fitting, sealing fitting, flexible fitting, cable fitting, enclosure, and item of equipment installed within a classified location shall be listed by a Nationally Recognized Testing Laboratory for the class, division or zone, and group of that location, and shall bear the listing mark.
+
+### Equipment and fittings of a protection technique that depends on a listing, including explosionproof, dust-ignitionproof, intrinsically safe, nonincendive, and pressurized equipment, shall be listed to the UL standard for that technique named in the Referenced Standards section or to the equivalent standard of another Nationally Recognized Testing Laboratory.
+
+### Unlisted equipment and fittings shall not be installed within a classified location.
+
+### A field evaluation of unlisted equipment by a Nationally Recognized Testing Laboratory is not an acceptable substitute for a listing in a Division 1 or Zone 0 or Zone 1 location.
+
+## Responsibility for the Classification {toc}
+
+### The Engineer of Record classifies each location, and the classification drawings are a contract document; the Contractor shall not reclassify a location, extend or reduce an envelope, or install an installation to a classification other than the one shown.
+
+### Where equipment the Contractor furnishes, including a packaged system, introduces a source of release not shown on the classification drawings, including a vent, a hatch, a drain, a relief valve discharge, or a sample point, the Contractor shall report the source to the Engineer of Record before the equipment is set, and shall not install electrical equipment around it until the Engineer of Record has confirmed or revised the classification.
+
+### A hazardous-location classification is engineering design, and delegating it to a Contractor or an equipment supplier leaves the one determination every other requirement depends on with the party least able to see the whole facility. The Contractor's obligation is to build to the classification and to report what the classification did not anticipate. {note}
+
+# Area Classification {toc}
+
+## Classification Deliverable {toc}
+
+### The classification drawings shall identify each classified location by class, division or zone, and group, shall show the extent of each envelope in plan and in elevation, shall name the material and the basis document from which each classification is derived, and shall be available to the Contractor, the inspector, and the Owner's operating staff as NFPA 70 500.4(A) requires.
+
+### NFPA 70 500.4(A) requires every area designated as a hazardous (classified) location to be documented, and the documentation to be available to those who design, install, inspect, maintain, or operate the electrical equipment. The classification drawings are that documentation on this project, and the record copy delivered at closeout is how it stays available after the Contractor has left. {note}
+
+### Each room, section, and area shall be classified individually, as NFPA 70 500.5(A) requires, so that a classified envelope around a source does not classify a whole building and an unclassified room beside a classified one is shown as unclassified.
+
+### The classification basis documents applied on the project shall be as indicated in the datasheet.
+
+```datasheet
+label: Classification Basis Documents
+type: checkbox
+options:
+ - "NFPA 497 for flammable gases, vapors and liquids"
+ - "NFPA 499 for combustible dusts"
+ - "NFPA 820 for wastewater treatment and collection facilities"
+ - "NFPA 30 for flammable and combustible liquid storage and handling"
+ - "NFPA 30A for motor fuel dispensing and repair garages"
+ - "NFPA 58 for liquefied petroleum gas"
+ - "NFPA 33 for spray application"
+ - "API RP 500 for petroleum facilities under the Division system"
+ - "API RP 505 for petroleum facilities under the Zone system"
+ - "ANSI/ISA-60079-10-1 for gas atmospheres under the Zone system"
+constraint: all_of
+```
+
+### NFPA 70 500.4(B) names the recommended practices and codes a classification is drawn from, and each covers a different source: NFPA 497 assigns the group and the autoignition temperature of a flammable gas, vapor or liquid and gives the envelopes around process sources; NFPA 499 does the same for combustible dusts; NFPA 820 classifies the spaces of a wastewater collection and treatment facility by what they handle and how they are ventilated; NFPA 30, 30A and 58 classify the areas around liquid storage, fuel dispensing and propane; and API RP 500 and RP 505 are the petroleum industry's practices, adopted on an industrial Owner's site by the Owner's standard. A project lists the documents its classification was drawn from so that the Contractor and the inspector read the envelopes against the right source. {note}
+
+## Classification System {toc}
+
+### The classification system applied on the project shall be as indicated in the datasheet.
+
+```datasheet
+label: Classification System
+type: radio
+options:
+ - "Division system, NFPA 70 Articles 500 through 504"
+ - "Zone system, NFPA 70 Articles 505 and 506"
+default: "Division system, NFPA 70 Articles 500 through 504"
+```
+
+### The Division system classifies by the likelihood of a flammable atmosphere in two steps, Division 1 where it exists in normal operation and Division 2 where it exists only under abnormal conditions, and nearly all equipment in the US market, nearly all inspectors, and NFPA 820 itself are written to it, which is why it is the default. The Zone system of Articles 505 and 506 classifies in three steps, Zone 0 for a continuous atmosphere, Zone 1 for one in normal operation and Zone 2 for one under abnormal conditions, which admits a wider set of protection techniques, among them increased safety and the Zone 2 techniques that replace an explosionproof enclosure with a lighter one; it is selected where the Owner's facilities standard, an international equipment supplier, or a petroleum process already runs on it. {note}
+
+### Where the Zone system is selected, a Zone 2 location may abut but shall not overlap a Division 2 location, and a Zone 0 or Zone 1 location shall not abut a Division 1 or Division 2 location, as NFPA 70 505.7 requires.
+
+### Where the Zone system is selected, the requirements of the Zone-System Wiring and Marking article of this standard apply in place of the Division-system wiring method and marking clauses.
+
+## Wastewater Facilities Under NFPA 820 {toc}
+
+### In a wastewater treatment or collection facility, the spaces NFPA 820 classifies, including wet wells, screening and grit rooms, headworks, digesters and their galleries, gas handling and compressor rooms, sludge pumping and dewatering areas, and the spaces around their hatches, vents and drains, shall be classified on the classification drawings under the NFPA 820 tables for the process they house and the ventilation furnished.
+
+### NFPA 820 classifies most of its spaces at a lower division, or as unclassified, where the space is continuously ventilated at the rate the standard sets, and the ventilation is monitored. The division shown on the classification drawings for such a space is therefore a classification on condition: it holds only while the ventilation designed under the mechanical documents is installed, runs continuously, and alarms on failure. This standard states the dependency once, here; the ventilation itself is mechanical scope. {note}
+
+### Where the classification drawings show a division that depends on continuous ventilation, the Contractor shall not energize equipment listed for that division, or for an unclassified location, within the space until the ventilation serving it is operating and its failure alarm has been proven.
+
+### Spaces that handle chlorine, sulfur dioxide, or another gas that is corrosive or toxic but not flammable are not classified under Articles 500 through 516 on that account; they are corrosive locations, and the enclosure and raceway corrosion requirements of the standards that govern the equipment and raceway in them apply instead. {note}
+
+## Flammable Liquid, Fuel and Propane Areas {toc}
+
+### The areas around fuel oil sumps, vents and fill stations, fuel dispensers and their tanks, propane containers and their vaporizers, and flammable liquid storage and handling shall be classified on the classification drawings under NFPA 30, NFPA 30A, or NFPA 58 for the source, and the sentences of [[sync/fuel-oil-systems]] and [[sync/fuel-dispensing-and-storage-tanks]] that point their devices at those drawings remain in force.
+
+### A tank or a pump handling a Class II or Class III liquid below its flash point does not by itself classify the room it occupies, but a vent termination, a sump, a fill, and any liquid handled above its flash point do; the classification drawings make that distinction for each source rather than leaving it to the installer. {note}
+
+## Combustible Dust Areas {toc}
+
+### Areas in which a combustible dust is handled, including lime, polymer, activated carbon, grain, wood and metal dusts, shall be classified on the classification drawings as Class II locations of the group NFPA 499 assigns to the dust, and areas handling ignitable fibers or flyings as Class III locations.
+
+### A combustible dust is classified by group under NFPA 70 500.6(B): Group E for conductive metal dusts, Group F for carbonaceous dusts, and Group G for the remaining dusts, including flour, grain, wood, plastics and chemicals. The group matters to the installation because dust-ignitionproof equipment is listed by group, and Group E in particular forbids some wiring methods and fittings the other groups permit. {note}
+
+## Temperature Code {toc}
+
+### Equipment installed in a Class I or Class II location shall carry a temperature code, or a marked operating temperature, at or below the code required for that location, and the required code at each location shall be as indicated in the datasheet.
+
+```datasheet
+label: Temperature Code Required at Each Classified Location
+type: select
+options:
+ - "T1"
+ - "T2"
+ - "T3"
+ - "T4"
+ - "T5"
+ - "T6"
+default: deferred
+drawing_ref: "the hazardous area classification drawings"
+```
+
+### A temperature code is the maximum surface temperature a listed item of equipment reaches at its rated load in a 40°C ambient, from T1 at 450°C down to T6 at 85°C with the subdivisions of NFPA 70 Table 500.8(C)(4) between, and the code required at a location is the one whose temperature sits below the autoignition temperature of the material that classifies it. The code follows from the material, which the classification drawings name, so the field defers to them: a methane atmosphere in a wet well admits T1 equipment, while a gasoline or diesel vapor requires T2 or T3 and a few solvents require T4 or lower. {note}
+
+### Equipment of a kind that does not produce heat in normal operation, including boxes, fittings, and conduit bodies, need not carry a temperature code, as NFPA 70 500.8(C) permits.
+
+# Protection Techniques {toc}
+
+## Techniques by Division {toc}
+
+### NFPA 70 500.7 permits a defined set of protection techniques, each for the divisions it names: an explosionproof enclosure and intrinsic safety are acceptable in Division 1 and Division 2 of a Class I location; dust-ignitionproof equipment in Class II; a purged and pressurized enclosure under NFPA 496 in the division its type is designed for; nonincendive circuits, nonincendive equipment, nonincendive components, oil immersion and hermetically sealed equipment in Division 2 of the class they are listed for; and combustible gas detection as a technique only in the circumstances 500.7(K) states. A protection technique is chosen per kind of equipment, not per location: in one Division 1 wet well, the submersible pump is explosionproof, the level transmitter is intrinsically safe, the junction box is explosionproof, and the control panel is outside the location altogether. {note}
+
+### Each item of electrical equipment installed within a classified location shall be protected by a technique NFPA 70 500.7 permits for the class and division of that location.
+
+### The protection technique of each equipment product furnished under another standard shall be as that standard specifies for the location, and this standard governs the enclosures, boxes, fittings, raceways, cables, seals and bonding that connect them.
+
+## Explosionproof and Dust-Ignitionproof Enclosures {toc}
+
+### An explosionproof enclosure is listed to UL 1203 to contain an internal explosion of the gas or vapor of its group and to cool the escaping gases below the ignition temperature of the atmosphere outside, through the ground joints and threaded paths of its construction. It is not sealed against the atmosphere: it works because the atmosphere inside it can ignite without igniting the room. A dust-ignitionproof enclosure, listed to the same standard for Class II, works the other way, by excluding dust and by keeping its surface temperature below the ignition temperature of the dust layer on it. Both are NEMA 250 enclosures, Type 7 for Class I and Type 9 for Class II, and [[sync/common-work-results-electrical]] already requires that an enclosure in a classified location be Type 7 or Type 9 as the classification requires. {note}
+
+### Explosionproof and dust-ignitionproof enclosures, boxes and fittings shall be installed with every cover in place, every cover bolt installed and torqued, every unused opening closed with a listed plug, and every threaded joint made up wrenchtight with not fewer than five threads fully engaged, or the thread engagement the listing of the equipment states, as NFPA 70 500.8(E) requires.
+
+### Explosionproof and dust-ignitionproof enclosures shall not be drilled, tapped, welded, or modified in the field except as the listing permits.
+
+### Flame-path and ground-joint surfaces of explosionproof enclosures shall be protected from damage, corrosion and paint during storage and installation, shall be cleaned before the cover is closed, and shall not be gasketed, greased with an unlisted compound, or shimmed.
+
+### A flame path works because its gap and its length are within the listing; a scratch, a buildup of paint, or a gasket the listing did not include changes the gap, and an explosionproof enclosure whose joint has been opened and closed carelessly is an ordinary box with a heavy lid. {note}
+
+### Conduit entries into an explosionproof or dust-ignitionproof enclosure shall be threaded entries, and a cable entry shall be made with a cable fitting listed for the enclosure, the cable, and the location.
+
+## Enclosures in Class I, Division 1 Locations {toc}
+
+### The protection technique of control panels, junction enclosures larger than a device box, local control stations, and other field enclosures installed within a Class I, Division 1 location shall be as indicated in the datasheet.
+
+```datasheet
+label: Field Enclosure Protection Technique, Class I Division 1
+type: select
+options:
+ - "Explosionproof enclosure"
+ - "Purged and pressurized enclosure under NFPA 496"
+ - "Not applicable, no field enclosures inside Division 1 locations"
+```
+
+### An explosionproof enclosure is self-contained and needs no protective gas supply, but it is cast metal, heavy, limited in size, must be opened only with the circuit de-energized, and seals every conduit entering it; it suits a junction box, a local control station, and a small terminal enclosure. A purged and pressurized enclosure under NFPA 496 is an ordinary sheet-metal enclosure kept at a positive pressure of clean air or inert gas, so it can be any size and can house general-purpose components, at the cost of a protective gas supply that must never fail, a purge before energization, and a control system that de-energizes or alarms on loss of pressure; it suits an analyzer house, a large control panel, or a drive enclosure that cannot be moved out of the location. On most water and wastewater projects neither is chosen, because the panel is placed outside the location and only listed devices and explosionproof boxes sit inside it, which is the third option; no option is distinctly the norm across projects, so the field carries no default. {note}
+
+### Regardless of the technique selected, the control panel serving a classified location shall be located outside it wherever the drawings permit, and the Contractor shall report any panel location shown inside a classified envelope before the panel is set.
+
+## Enclosures in Class I, Division 2 Locations {toc}
+
+### The protection technique of control panels, junction enclosures larger than a device box, local control stations, and other field enclosures installed within a Class I, Division 2 location shall be as indicated in the datasheet.
+
+```datasheet
+label: Field Enclosure Protection Technique, Class I Division 2
+type: select
+options:
+ - "Nonincendive equipment in a general-purpose enclosure"
+ - "Explosionproof enclosure"
+ - "Purged and pressurized enclosure under NFPA 496"
+ - "Not applicable, no field enclosures inside Division 2 locations"
+```
+
+### Division 2 admits an enclosure that is not explosionproof provided nothing inside it arcs, sparks, or runs hot in normal operation, so a terminal enclosure with no switching, or a panel whose components are nonincendive under UL 121201, can be a Type 4X enclosure with a Division 2 listing on the assembly; this is lighter, cheaper, and easier to open than an explosionproof box. An explosionproof enclosure is chosen in Division 2 where the enclosure contains an arcing device, where the Owner standardizes on one enclosure family across both divisions, or where a Division 2 space may be reclassified upward when its ventilation is lost. A Type Z purged enclosure under NFPA 496 reduces a Division 2 interior to unclassified and houses general-purpose components at the cost of the protective gas supply. No option is distinctly the norm, so the field carries no default. {note}
+
+### Where a general-purpose enclosure is selected for Division 2, every device inside it that makes or breaks a circuit, or that operates above the temperature code of the location, shall itself be listed for the location, and the assembly shall be listed under UL 698A or UL 121201 for Class I, Division 2.
+
+## Purged and Pressurized Enclosures {toc}
+
+### Requirements in this article apply where a purged and pressurized enclosure is selected under this standard or under the standard that governs the equipment in it; this article does not itself select pressurization. {note}
+
+### Where pressurization is selected, the NFPA 496 type of each purged and pressurized enclosure shall be as indicated in the datasheet.
+
+```datasheet
+label: Purge Type Under NFPA 496
+type: select
+options:
+ - "Type X"
+ - "Type Y"
+ - "Type Z"
+ - "Not applicable, no purged enclosure"
+```
+
+### NFPA 496 defines three types by the reduction each achieves: Type X reduces a Division 1 interior to unclassified and must de-energize the enclosure automatically on loss of pressure; Type Y reduces a Division 1 interior to Division 2, so the components inside must themselves be Division 2 equipment, and loss of pressure alarms; Type Z reduces a Division 2 interior to unclassified and loss of pressure alarms or indicates. Type X buys general-purpose components in Division 1 at the cost of an automatic trip that stops the process when the air supply fails; Type Y keeps the process running through an air failure at the cost of Division 2 components inside; Type Z is the Division 2 case. The type follows from the division of the location and the consequence of a trip, so the field carries no default. {note}
+
+### Each purged and pressurized enclosure shall be furnished with a listed pressurization control unit, a protective gas supply from a source outside every classified location, a pressure or flow indicator visible from outside the enclosure, and the alarm or de-energization function NFPA 496 requires for its type.
+
+### A Type X enclosure shall be purged with the exchange volume NFPA 496 requires before power is applied to the equipment inside it, and shall be interlocked to de-energize that equipment on loss of pressure.
+
+### The conduit entries of a pressurized enclosure shall be sealed within 18 in. of the enclosure as NFPA 70 501.15(A)(2) requires, so that the protective gas does not escape into the raceway system and the raceway atmosphere does not enter the enclosure.
+
+### Each purged and pressurized enclosure shall carry a nameplate on its exterior stating the NFPA 496 type, the minimum protective gas pressure, and the warning that the enclosure shall not be opened unless the area is known to be free of flammable atmosphere or the power has been removed.
+
+## Intrinsically Safe Systems {toc}
+
+### Requirements in this article apply where an intrinsically safe circuit enters a classified location, whether the circuit is selected under this standard or under the standard that governs the field device; this article does not itself select intrinsic safety for any device. {note}
+
+### An intrinsically safe system is safe because every element of the loop, the barrier or isolator, the cable, and the field device, is listed and matched so that the energy the circuit can store and release is below the ignition energy of the atmosphere, even under two faults; the cable is governed by [[sync/instrumentation-and-control-cable]], which states its published parameters, the entity-parameter sum on the cable schedule and the light blue jacket, and the barrier and its panel by [[sync/industrial-control-panels]]. This article governs what is installed in the classified location and in the raceways and enclosures between: the control drawing, the separation, the grounding, the identification and the seals. {note}
+
+### Each intrinsically safe circuit shall be installed in accordance with the control drawing of its barrier or isolator and of its field device, as NFPA 70 504.10(A) requires, with no device, cable, or connection in the loop that the control drawing does not show.
+
+### Associated apparatus, meaning the barrier or isolator, shall be installed outside the classified location, or within it only in an enclosure protected by another technique this standard permits for the location, as NFPA 70 504.10(B) requires.
+
+### Intrinsically safe circuit conductors shall be separated from the conductors of every non-intrinsically-safe circuit as NFPA 70 504.30 requires, and the separation method within field enclosures shall be as indicated in the datasheet.
+
+```datasheet
+label: Intrinsically Safe Circuit Separation in Field Enclosures
+type: select
+options:
+ - "Dedicated enclosures for intrinsically safe circuits"
+ - "Grounded metal partition within a shared enclosure"
+ - "Separation of 2 in. with the intrinsically safe conductors secured"
+```
+
+### NFPA 70 504.30 accepts three separations inside an enclosure: a dedicated enclosure, a grounded metal or approved insulating partition, or a clear 2 in. between the intrinsically safe terminals and conductors and every other terminal and conductor with the conductors secured so the spacing is kept. A dedicated enclosure is the easiest to inspect and the hardest to defeat during maintenance, at the cost of a second box at every device cluster; a partition shares the box; the 2 in. spacing costs nothing but depends on the next electrician who opens the box. The choice is a project policy and no option is distinctly the norm, so the field carries no default. {note}
+
+### Intrinsically safe circuit conductors shall not share a raceway, cable, or cable tray with non-intrinsically-safe conductors except with the separation NFPA 70 504.30(A)(1) permits, and shall not be run on a spare pair of a cable carrying any other circuit.
+
+### Intrinsically safe apparatus, associated apparatus, and cable shields shall be grounded as NFPA 70 504.50 and the control drawing require, through an intrinsically safe ground bus that is insulated from the enclosure, connected to the grounding electrode system by a dedicated conductor, and installed under ANSI/ISA-RP12.06.01.
+
+### The intrinsically safe ground bus shall be bonded to the grounding electrode system by a path whose resistance does not exceed 1 ohm, measured and recorded before the first loop is energized.
+
+### A shunt-diode barrier passes fault energy to ground, and the ground it passes it to must be the plant's grounding electrode by a path of its own; a barrier grounded through the panel enclosure and a chain of locknuts has a fault path the control drawing did not calculate. {note}
+
+### Intrinsically safe circuits shall be identified at every terminal and junction location and at intervals not exceeding 25 ft along the wiring, with the words INTRINSIC SAFETY WIRING or the light blue color NFPA 70 504.80 permits, and the identification of the cable itself is governed by [[sync/instrumentation-and-control-cable]].
+
+### Intrinsically safe apparatus in a classified location shall be bonded as NFPA 70 504.60 requires, by the bonding means of the Bonding in Classified Locations section.
+
+### Raceways and cables carrying intrinsically safe circuits that are required to be sealed under the Conduit and Cable Seals section shall be sealed to minimize the passage of gas, vapor or dust as NFPA 70 504.70 requires; the seals need not be explosionproof.
+
+## Nonincendive Equipment and Circuits {toc}
+
+### Nonincendive equipment, nonincendive circuits, and nonincendive components shall be installed only in Division 2 locations of the class and group they are listed for, as NFPA 70 500.7(F), (G) and (H) permit, and nonincendive field wiring shall be installed in accordance with the control drawing of the apparatus as NFPA 70 501.10(B)(3) requires.
+
+### A nonincendive circuit or item of equipment does not release enough energy, or reach a temperature high enough, to ignite the atmosphere under normal operating conditions; unlike intrinsic safety it is not evaluated under fault, which is why NFPA 70 confines it to Division 2, where the atmosphere and the fault are not expected together. It is the technique that lets a Division 2 location be served by ordinary-looking instruments, network devices and panels listed to UL 121201. {note}
+
+## Oil Immersion and Hermetically Sealed Equipment {toc}
+
+### Oil-immersed contacts and hermetically sealed equipment shall be installed only in Division 2 locations and only where listed for the location, as NFPA 70 500.7(I) and (J) permit, and shall be mounted in the orientation their listing requires.
+
+## Combustible Gas Detection as a Protection Technique {toc}
+
+### Whether a combustible gas detection system is permitted as a protection technique on the project shall be as indicated in the datasheet.
+
+```datasheet
+label: Combustible Gas Detection as a Protection Technique
+type: radio
+options:
+ - "Permitted under NFPA 70 500.7(K)"
+ - "Not permitted as a protection technique"
+```
+
+### NFPA 70 500.7(K) permits a listed combustible gas detection system as a protection technique only in an industrial establishment with restricted public access and qualified maintenance, and only in three cases: a Division 1 location so classified because its ventilation is inadequate, where Division 2 equipment is then permitted; a building that opens into a Division 2 location but contains no source of its own, where unclassified equipment is then permitted; and the interior of a control panel that measures flammable material, where Division 2 equipment is then permitted. The technique trades explosionproof construction for a detection system that must be listed for the gas, calibrated on a schedule, and documented to the Authority Having Jurisdiction, and it moves the safety of the installation from hardware to a maintenance program; a plant with a staffed instrument shop accepts that trade, and a remote unattended station rarely does. The choice is the Owner's, so the field carries no default. {note}
+
+### Where combustible gas detection is permitted as a protection technique, it shall be applied only in the cases NFPA 70 500.7(K) enumerates, with the detection equipment listed for the specific gas or vapor present, and the equipment is furnished under [[sync/gas-detection-systems]].
+
+### Where combustible gas detection is applied as a protection technique, the equipment it protects shall be interlocked to de-energize, or the area to alarm, at the gas concentration the submitted documentation states, and the Contractor shall prove the interlock during the classified-location inspection.
+
+# Wiring Methods {toc}
+
+## Class I, Division 1 Wiring {toc}
+
+### The wiring method for circuits within a Class I, Division 1 location shall be as indicated in the datasheet, and shall be one NFPA 70 501.10(A) permits.
+
+```datasheet
+label: Class I Division 1 Wiring Method
+type: select
+options:
+ - "Threaded rigid metal conduit"
+ - "Threaded steel intermediate metal conduit"
+ - "Type MI cable with listed termination fittings"
+ - "Type MC-HL cable with listed termination fittings"
+ - "Type ITC-HL cable with listed termination fittings"
+default: "Threaded rigid metal conduit"
+```
+
+### Threaded rigid metal conduit is the Division 1 wiring method of nearly every water, wastewater and general industrial plant, because every explosionproof box, fitting and seal is made for it, the conduit itself is the flame path between devices, and the trade knows it; it is the default. Threaded steel intermediate metal conduit is the same system in a lighter wall and is chosen where weight and cost matter and the Owner accepts it. Type MI cable is a copper-sheathed mineral-insulated cable that needs no conduit and survives fire, chosen for a circuit that must survive the event it is protecting against. Type MC-HL and Type ITC-HL are cables listed for Division 1 with a continuous gas-and-vaportight corrugated sheath, an overall jacket and listed fittings, permitted by NFPA 70 501.10(A) only in an industrial establishment with restricted public access where qualified persons maintain the installation, and chosen in a process plant that runs cable in tray and will not thread conduit through a unit. {note}
+
+### Type MC-HL and Type ITC-HL cable shall be used in a Division 1 location only where the facility is an industrial establishment with restricted public access and qualified maintenance, as NFPA 70 501.10(A) conditions their use, and the Engineer of Record shall confirm that condition in writing before either is selected in the datasheet.
+
+### Where the wiring method selected in the datasheet is conduit, specific circuits for which a cable method the article permits is designated on [[drawing: the conduit and cable schedule]] may be run in that cable; circuits not so designated shall be run in the method the datasheet selects.
+
+### All boxes and fittings in a Class I, Division 1 location shall be listed for Class I, Division 1, as NFPA 70 501.10(A) requires.
+
+### Rigid metal conduit and intermediate metal conduit in a Division 1 location shall be threaded with a tapered NPT thread, made up wrenchtight at every joint and entry, and joined only with threaded couplings; running threads, threadless couplings, set-screw and compression fittings shall not be used.
+
+## Class I, Division 2 Wiring {toc}
+
+### The wiring method for circuits within a Class I, Division 2 location shall be as indicated in the datasheet, and shall be one NFPA 70 501.10(B) permits.
+
+```datasheet
+label: Class I Division 2 Wiring Method
+type: select
+options:
+ - "Threaded rigid metal conduit"
+ - "Threaded steel intermediate metal conduit"
+ - "Type MC cable with listed fittings"
+ - "Type MI cable with listed termination fittings"
+ - "Type TC-ER cable with listed fittings"
+ - "Type PLTC-ER and ITC-ER cable with listed fittings"
+default: "Threaded rigid metal conduit"
+```
+
+### NFPA 70 501.10(B) permits in Division 2 every Division 1 method and adds the ordinary industrial cables with listed fittings: Type MC, Type TC and TC-ER in tray and as the exposed run between tray and equipment, and the instrumentation cables Type PLTC and PLTC-ER and Type ITC and ITC-ER. Threaded rigid metal conduit is the default because a plant that threads conduit in its Division 1 spaces runs the same system through the Division 2 envelope around them rather than changing method at a boundary nobody can see. Type MC cable is chosen in a process plant whose unclassified areas are already cabled, Type TC-ER where tray is the plant's distribution, Type MI for a circuit that must survive a fire, and Type PLTC-ER and ITC-ER for the instrumentation circuits of a plant that trays its signal cable; each trades the flame-path conduit system for lighter installation and depends on the listed fitting at every entry. {note}
+
+### Whether boxes and fittings in a Class I, Division 2 location are explosionproof shall be as indicated in the datasheet.
+
+```datasheet
+label: Boxes and Fittings in Class I Division 2
+type: radio
+options:
+ - "General-purpose boxes and fittings where NFPA 70 501.10(B) permits them"
+ - "Explosionproof boxes and fittings throughout"
+```
+
+### NFPA 70 501.10(B)(4) does not require a box or fitting in Division 2 to be explosionproof unless it contains an arcing device or a device whose temperature exceeds the code; a general-purpose cast or Type 4X box with threaded hubs is therefore legal for a splice or a pull point, lighter, and cheaper. Many Owners nonetheless specify explosionproof boxes throughout both divisions so that the installation does not depend on an inspector tracing which box has a contact in it, and so that a Division 2 space that loses its ventilation and is reclassified Division 1 needs no rework. Neither policy is distinctly the norm, so the field carries no default. {note}
+
+### Regardless of the datasheet selection, every box and fitting in a Division 2 location that contains a make-or-break contact, a switch, a fuse, or a device operating above the temperature code of the location shall be explosionproof, or the device shall be of a protection technique this standard permits for Division 2.
+
+## Class II and Class III Wiring {toc}
+
+### The wiring method for circuits within a Class II, Division 1 location shall be as indicated in the datasheet, and shall be one NFPA 70 502.10(A) permits.
+
+```datasheet
+label: Class II Division 1 Wiring Method
+type: select
+options:
+ - "Threaded rigid metal conduit"
+ - "Threaded steel intermediate metal conduit"
+ - "Type MI cable with listed termination fittings"
+ - "Type MC-HL cable with listed termination fittings"
+default: "Threaded rigid metal conduit"
+```
+
+### The wiring method for circuits within a Class II, Division 2 location and within a Class III location shall be as indicated in the datasheet, and shall be one NFPA 70 502.10(B) or 503.10 permits.
+
+```datasheet
+label: Class II Division 2 and Class III Wiring Method
+type: select
+options:
+ - "Rigid metal conduit"
+ - "Intermediate metal conduit"
+ - "Electrical metallic tubing"
+ - "Type MC cable with listed fittings"
+ - "Type MI cable with listed termination fittings"
+ - "Type TC, PLTC and ITC cable in cable tray with listed fittings"
+```
+
+### A dust location is protected by keeping dust out of the enclosure and the surface temperature down, not by containing an explosion, so NFPA 70 permits in Class II, Division 2 and Class III the same methods as an ordinary industrial building, including electrical metallic tubing, dusttight wireways and cable in tray, provided the fittings and boxes are dusttight. Class II, Division 1 keeps the threaded conduit and listed cable methods of Class I, Division 1, and threaded rigid metal conduit is its default for the same reasons; in Division 2 and Class III the plant's ordinary method governs, which differs by plant, so that field carries no default. In a Group E location, the conductive dust forbids some fittings and boxes the other groups permit, and the listing of each must name Group E. {note}
+
+### Boxes and fittings in a Class II location shall be dusttight with threaded bosses, and boxes and fittings in which taps, joints or terminal connections are made, and all boxes and fittings in a Group E location, shall be identified for Class II locations as NFPA 70 502.10(A) requires.
+
+### Boxes and fittings in a Class III location shall be dusttight, as NFPA 70 503.10 requires.
+
+## Flexible Connections {toc}
+
+### Flexible connections to motors, actuators, and other equipment subject to vibration or movement within a Class I, Division 1 location shall be made by the method indicated in the datasheet, as NFPA 70 501.10(A)(2) permits.
+
+```datasheet
+label: Flexible Connection Method, Class I Division 1
+type: radio
+options:
+ - "Listed explosionproof flexible fittings"
+ - "Flexible cord listed for extra-hard usage with listed cord connectors"
+default: "Listed explosionproof flexible fittings"
+```
+
+### Flexible connections within a Class I, Division 2 location shall be made by the method indicated in the datasheet, as NFPA 70 501.10(B)(2) permits.
+
+```datasheet
+label: Flexible Connection Method, Class I Division 2
+type: select
+options:
+ - "Liquidtight flexible metal conduit with listed fittings"
+ - "Listed flexible metal fittings"
+ - "Flexible metal conduit with listed fittings"
+ - "Liquidtight flexible nonmetallic conduit with listed fittings"
+ - "Flexible cord listed for extra-hard usage with listed bushed fittings"
+default: "Liquidtight flexible metal conduit with listed fittings"
+```
+
+### Division 1 admits only a listed explosionproof flexible fitting, a braided flame-path coupling made for the purpose, or flexible cord under NFPA 70 501.140 for equipment that must be moved for maintenance, such as a submersible pump; the explosionproof fitting is the default because it keeps the conduit system continuous and the cord is the exception for portable or withdrawable equipment. Division 2 admits liquidtight flexible metal conduit with listed fittings, which is the default because it is the motor connection of every unclassified plant and needs only a bonding jumper to qualify; listed flexible metal fittings where the Owner standardizes on one fitting family across both divisions; ordinary flexible metal conduit where the location is dry; liquidtight flexible nonmetallic conduit where the atmosphere corrodes steel; and flexible cord for movable equipment. {note}
+
+### Flexible metal conduit and liquidtight flexible metal conduit in a classified location shall not serve as the sole equipment grounding conductor, and shall be furnished with the bonding jumper NFPA 70 501.30(B) or 502.30(B) requires.
+
+### Flexible cord in a classified location shall be of a type listed for extra-hard usage, shall contain an equipment grounding conductor, shall be supported so that no tension is transmitted to the terminals, and shall enter the enclosure through a listed cord connector that seals the cord where the enclosure requires a seal.
+
+## Raceway Corrosion Protection in Classified Corrosive Spaces {toc}
+
+### Where the wiring method in a classified location that the classification drawings or the process documents identify as corrosive, including a wet well, a headworks, a digester gallery, a sludge dewatering room, or a chemical room, is threaded conduit, the conduit, its couplings and its fittings shall be of the construction indicated in the datasheet.
+
+```datasheet
+label: Raceway Corrosion Protection in Classified Corrosive Spaces
+type: select
+options:
+ - "Galvanized steel rigid metal conduit"
+ - "PVC-coated galvanized rigid steel conduit"
+ - "Stainless steel rigid metal conduit"
+ - "Aluminum rigid metal conduit"
+```
+
+### Hydrogen sulfide, chlorine vapor, and a wet atmosphere attack galvanized steel conduit at the threads first, which is exactly where the flame path is, so the corrosion protection of a classified raceway is a protection-technique question and not only a service-life one. Galvanized steel conduit under UL 6 serves a space that is classified but dry and clean. PVC-coated galvanized rigid steel conduit under NEMA RN 1 keeps the steel flame path and adds a bonded exterior coating and a urethane interior, and is the construction of most wet wells and headworks, at the cost of coated fittings throughout, coating repair at every cut, and strap-wrench installation. Stainless steel rigid metal conduit under UL 6A resists the atmosphere without a coating that can be damaged, at a higher material cost and with stainless fittings and boxes to match. Aluminum rigid metal conduit under UL 6A is light and resists hydrogen sulfide, but is attacked by concrete, by chlorides, and by contact with dissimilar metals, and must be isolated from each. The space and the Owner's experience decide, and no option is distinctly the norm, so the field carries no default. {note}
+
+### Explosionproof boxes, fittings and sealing fittings in a classified corrosive space shall be of a material and finish compatible with the conduit construction selected in the datasheet, and a PVC-coated conduit system shall use PVC-coated fittings, boxes and seals throughout.
+
+### Dissimilar metals in a classified raceway system shall be separated by a listed fitting or isolating means that does not interrupt the bonding path.
+
+## Underground Raceways Entering Classified Locations {toc}
+
+### An underground raceway serving a classified location may be rigid polyvinyl chloride conduit or reinforced thermosetting resin conduit where it is encased in concrete not less than 2 in. thick with not less than 24 in. of cover, with threaded rigid metal conduit or threaded steel intermediate metal conduit for the last 24 in. of the run to the point of emergence or of connection to the aboveground raceway, and an equipment grounding conductor in the run, as NFPA 70 501.10(A) permits; the duct bank itself is governed by [[sync/underground-ductbank]].
+
+### Underground raceways entering a classified location shall be sealed at the boundary as the Conduit and Cable Seals section requires, and shall be arranged to drain away from the classified enclosure.
+
+## Prohibited Wiring Methods {toc}
+
+### The following shall not be installed within a Class I, Division 1 location: electrical metallic tubing, rigid polyvinyl chloride or reinforced thermosetting resin conduit except encased underground as permitted above, nonmetallic sheathed cable, armored cable, flexible metal conduit and liquidtight flexible conduit, surface raceways, wireways, cable tray as a wiring method, and busway.
+
+### The following shall not be installed within a Class I, Division 2 location: electrical metallic tubing, rigid polyvinyl chloride or reinforced thermosetting resin conduit except encased underground, nonmetallic sheathed cable, armored cable, and surface raceways.
+
+### Set-screw, compression, threadless, and running-thread connections shall not be made in any conduit within a Class I location.
+
+### Each prohibited method is one whose joints are not a flame path, whose fittings are not listed for the location, or whose enclosure would not contain an explosion; a method the article does not list is prohibited whether or not it is named here. {note}
+
+## Zone-System Wiring and Marking {toc}
+
+### Requirements in this article apply where the Zone system is selected in the Classification System article; this article does not itself select the Zone system. {note}
+
+### Wiring within a Class I, Zone 0, Zone 1 or Zone 2 location shall be by a method NFPA 70 505.15 permits for that zone, and within a Zone 20, Zone 21 or Zone 22 location by a method NFPA 70 506.15 permits.
+
+### Seals in a Zone location shall be installed as NFPA 70 505.16 or 506.16 requires, bonding as NFPA 70 505.25 or 506.25 requires, and the Conduit and Cable Seals and Bonding sections of this standard apply as the Division-system equivalents of those sections.
+
+### Equipment in a Zone location shall be marked as NFPA 70 505.9(C) or 506.9(C) requires, with the class, the zone, the AEx symbol, the protection technique, the gas or dust group, the temperature class and the equipment protection level, and Division-marked equipment shall be installed in a Zone location only where NFPA 70 505.20 permits it for that zone.
+
+### Zone 2 admits every Division 2 method and Zone 1 every Division 1 method, so a Zone project built with Division-listed equipment and threaded conduit is a legal installation; what the Zone system changes is the marking the equipment carries and the techniques it adds, chiefly increased safety, which lets a Zone 1 motor or terminal box be an ordinary-looking enclosure built so that nothing inside can arc or overheat. {note}
+
+# Conduit and Cable Seals {toc}
+
+## Seal Locations {toc}
+
+### A listed sealing fitting shall be installed in each conduit entering an explosionproof enclosure in a Class I location where the enclosure contains a device that may produce an arc, a spark or a high temperature, or where the conduit is trade size 2 or larger and the enclosure contains splices, taps or terminals, within 18 in. of the enclosure, with only explosionproof unions, couplings, reducers, elbows, capped elbows and conduit bodies of the same trade size between the seal and the enclosure, as NFPA 70 501.15(A)(1) and 501.15(B)(1) require.
+
+### Where two or more explosionproof enclosures that require seals are connected by a nipple or a run of conduit not more than 36 in. long, a single seal in each such nipple or run located not more than 18 in. from either enclosure may serve both, as NFPA 70 501.15(A)(3) permits.
+
+### A listed sealing fitting shall be installed in each conduit leaving a Class I, Division 1 location, within 10 ft of the boundary on either side of it, with no union, coupling, box or fitting other than a listed explosionproof reducer at the seal between the seal and the boundary, as NFPA 70 501.15(A)(4) requires.
+
+### A listed sealing fitting shall be installed in each conduit leaving a Class I, Division 2 location, within 10 ft of the boundary, with rigid metal conduit or threaded steel intermediate metal conduit and no union, coupling, box or fitting other than a listed explosionproof reducer at the seal between the seal and the point where the conduit leaves the location, as NFPA 70 501.15(B)(2) requires.
+
+### A boundary seal is not required in a metal conduit run that contains no union, coupling, box or fitting and that passes completely through the classified location with no fitting within 12 in. of either boundary, as NFPA 70 501.15 permits.
+
+### A boundary seal keeps the flammable atmosphere in the classified location from traveling along the conduit, as a gas or as a condensed liquid, into the switchgear room or the control building at the other end; the seal within 18 in. of an arcing enclosure keeps an explosion in that enclosure from propagating down the conduit as a pressure wave that pre-compresses the gas in the next enclosure. The two seals do different jobs, which is why the article requires both and limits what may sit between each seal and the thing it protects. {note}
+
+### Where a raceway connects an enclosure required to be dust-ignitionproof in a Class II location to one that is not, the raceway shall be sealed by a permanent and effective seal, or shall be a horizontal run not less than 10 ft long, or a vertical run not less than 5 ft long extending downward from the dust-ignitionproof enclosure, as NFPA 70 502.15 permits, and a seal so provided need not be explosionproof.
+
+### A cable entering an explosionproof enclosure in a Class I location shall be sealed at the point of entry with a cable fitting listed for the cable, the enclosure and the location, as NFPA 70 501.15(D) and 501.15(E) require.
+
+### A cable with a gas-and-vaportight continuous sheath that can transmit gas or vapor through its core shall be sealed in the Division 1 location after the jacket and any other coverings are removed so that the compound surrounds each individual insulated conductor, as NFPA 70 501.15(D) requires.
+
+### Where a sentence of [[sync/packaged-pump-stations]], [[sync/level-sensors]], or another equipment standard states a seal location for its own equipment, that sentence applies to that equipment in addition to this section, and this section governs every other seal.
+
+## Sealing Fittings and Compound {toc}
+
+### Sealing fittings shall be listed for the class, division and group of the location, shall be of the same material system as the conduit they are installed in, and shall be installed in the orientation and at the accessible location their listing requires.
+
+### The sealing compound shall be listed for use with the sealing fitting in which it is poured, shall not be affected by the atmosphere of the location or the liquids it may contain, and shall have a melting point of not less than 93°C, as NFPA 70 501.15(C) requires.
+
+### The compound in each seal shall be not less than the trade size of the conduit in thickness and in no case less than 5/8 in., shall completely surround every conductor, and shall be supported by a fiber dam packed below it as the fitting manufacturer's instructions require.
+
+### No splice, tap or connection shall be made within a sealing fitting, and the cross-sectional area of the conductors in a seal shall not exceed 25 percent of the cross-sectional area of a rigid metal conduit of the same trade size unless the fitting is listed for a higher fill, as NFPA 70 501.15(C) requires.
+
+### A seal shall be poured only after every conductor passing through it has been installed and tested, and the conduit system has been inspected, and shall be poured before the circuit is energized.
+
+### A seal poured before the conductors are in cannot be, and a seal poured after an insulation test cannot hide a conductor that failed it; the pour date on the seal schedule is the record that the sequence was kept, and a conductor added after the pour means the seal is cut out and remade. {note}
+
+### Each poured seal shall be marked by the installer at the fitting with the date of the pour, and the date and the installer shall be entered on the seal schedule.
+
+### The Contractor shall cut out and replace, at the Contractor's expense, any seal that was poured before its conductors were installed, that has a conductor added or removed after the pour, or that on inspection shows an incomplete pour, a void, or compound that has not surrounded each conductor.
+
+### A seal schedule shall be maintained from the Action Submittal through closeout, shall list every seal installed, and shall be the record against which the classified-location inspection verifies that no required seal is missing.
+
+## Drainage {toc}
+
+### Where liquid or condensed vapor can collect in an enclosure or at any point in the raceway system in a Class I location, a listed drain seal, a drain fitting, or a breather-and-drain combination shall be installed at the low point to prevent accumulation or to permit periodic draining, as NFPA 70 501.15(F) requires.
+
+### Conduit in a classified location shall be installed to drain away from every explosionproof enclosure, and a conduit that enters an enclosure from above shall be sealed with a fitting that includes a drain where the run above it can collect condensation.
+
+### Breather and drain fittings shall be listed for the class, division and group of the location and shall be installed in the orientation their listing requires.
+
+### A wet well conduit that rises to a junction box on the hatch and then runs to the control panel pumps humid air up into itself on every level cycle, and the condensation collects at the seal; a drain seal at the low point is what keeps the compound dry and the enclosure above it from filling. {note}
+
+# Bonding in Classified Locations {toc}
+
+## Bonding of every raceway, fitting, box and enclosure within a classified location, and of the raceway system from the classified location back to the service equipment or to the point of grounding of the separately derived system that supplies it, shall be by the bonding means NFPA 70 250.100 and 501.30, 502.30 or 503.30 require, and [[sync/grounding-and-bonding]] states that requirement for the grounding system as a whole.
+
+## Locknut-bushing and double-locknut bonding shall not be used as the bonding means at any raceway fitting in a classified location or anywhere in the raceway path between a classified location and the service equipment or the separately derived system.
+
+## Where a raceway path between a classified location and the service equipment or the separately derived system includes a fitting that cannot be bonded by a threaded connection, a bonding jumper with listed bonding fittings or a bonding-type locknut or bushing shall be installed around the fitting.
+
+## The bonding path matters all the way back to the source because the fault current that could raise an arc at a fitting in the classified location flows through every fitting between the location and the source, and a loose locknut outside the location is as much an ignition source for the fault current passing through it as one inside. {note}
+
+## An equipment grounding conductor shall be installed in every raceway and cable within a classified location, sized under [[sync/grounding-and-bonding]], and the raceway shall not serve as the sole equipment grounding conductor.
+
+# Equipment Listing and Marking {toc}
+
+## Marking Required {toc}
+
+### Every item of equipment installed within a classified location shall be marked with the class, the group, and the operating temperature or temperature code it is listed for, as NFPA 70 500.8(C) requires, and the marking shall be legible from the installed position after installation.
+
+### Equipment listed for an ambient temperature range other than minus 25°C to plus 40°C shall be marked with its range, as NFPA 70 500.8(C) requires, and equipment installed outdoors in a classified location shall be listed for a range that includes [[parameter: site-ambient-temperature-minimum]] and [[parameter: site-ambient-temperature-maximum]].
+
+### The ambient range matters to the protection technique because a temperature code is set at a 40°C ambient and an explosionproof listing assumes the enclosure materials and gaskets behave within the range; a wet well hatch box in a northern winter or a sunlit digester roof in summer can be outside a listing that was never marked for it. {note}
+
+### The operating temperature or temperature code marked on each item of equipment shall not exceed the autoignition temperature of the material that classifies the location, as NFPA 70 500.8(D) requires, and shall be at or below the code indicated in the datasheet for that location.
+
+## Verification Against the Classification {toc}
+
+### Before any equipment is installed within a classified location, the Contractor shall verify that the class, division or zone, group, temperature code, and ambient range on its nameplate meet the classification of the location it is shown in, and shall record the verification on the listing schedule.
+
+### The Contractor shall report to the Engineer of Record, before installation, every item of equipment that is shown within a classified envelope and is not listed for that envelope, whether the equipment was furnished by the Contractor, by a packaged-system supplier, or by the Owner, and shall not install it until the Engineer of Record has directed the correction.
+
+### Packaged equipment, including pump stations, chemical feed skids, and gas handling skids, arrives with its own electrical devices, and the supplier's listing of the package as a whole does not establish that each device on it is listed for the envelope the package sits in; the listing schedule is checked device by device. {note}
+
+## Equipment Furnished Under Other Standards {toc}
+
+### Each equipment product installed within a classified location carries the hazardous-location enclosure and listing its own standard specifies for the location, and that standard governs the product: the explosionproof motor under [[sync/electric-motors]], the starter enclosure under [[sync/combination-motor-starters]], the analyzer and the instrument protection method under [[sync/analytical-instrumentation]], [[sync/level-sensors]], [[sync/flow-measurement]], [[sync/pressure-instrumentation]] and [[sync/temperature-instrumentation]], the actuator under [[sync/control-valves-and-actuators]], the heat-tracing circuit under [[sync/electric-heat-tracing]], the crane under [[sync/overhead-material-handling]], the dust collector under [[sync/dust-and-fume-collection]], the submersible pump under [[sync/submersible-solids-handling-pumps]], and the packaged station under [[sync/packaged-pump-stations]]. This standard states the listing and marking rule once and verifies every nameplate against the drawings; it does not respecify any product. {note}
+
+### Luminaires for hazardous (classified) locations are not yet owned by a SynC standard; a luminaire installed within a classified location shall be listed for the class, division or zone, group and temperature code of that location and shall be installed under this standard until a standard owns the product. {note}
+
+# Specific Occupancies {toc}
+
+## Where the project includes an occupancy NFPA 70 Articles 511 through 516 address, the classification drawings shall apply that article and its referenced code, and the installation shall comply with it in addition to this standard. {note}
+
+- A commercial repair garage is classified under NFPA 70 Article 511, with the classification of the floor area depending on the ventilation and the fuel handled, and a parking garage is unclassified unless the article classifies it
+- An aircraft hangar is classified under NFPA 70 Article 513 and NFPA 409, with the floor pits and the space near the floor classified and the remainder depending on the aircraft and the ventilation
+- A motor fuel dispensing facility is classified under NFPA 70 Article 514 and the tables of NFPA 30A, and the sentences of [[sync/fuel-dispensing-and-storage-tanks]] that point its devices at the classification drawings remain in force
+- A bulk storage plant for flammable liquids is classified under NFPA 70 Article 515 and NFPA 30
+- A spray booth, dipping, or coating process is classified under NFPA 70 Article 516 and NFPA 33, with the booth interior and the space around its openings classified
+
+## The specific-occupancy articles do not replace the general rules of Articles 500 through 504; they classify the occupancy and add a few requirements of their own, and the wiring, sealing, bonding and marking of this standard apply within every envelope they draw. {note}
+
+# Inspection and Verification {toc}
+
+## Classified-Location Inspection Before Energization {toc}
+
+### Before any circuit entering a classified location is energized, the installation within and at the boundary of that location shall be inspected, and the inspection shall be performed by the party indicated in the datasheet.
+
+```datasheet
+label: Classified-Location Inspection Before Energization
+type: radio
+options:
+ - "Inspection witnessed by the Engineer of Record before energization"
+ - "Inspection by the Contractor with a signed report submitted before energization"
+ - "Inspection by an independent inspector retained by the Owner before energization"
+```
+
+### A classified-location installation is checked once, with the covers off and the seals unpoured or freshly poured, and then concealed behind closed enclosures for the life of the plant; an inspection witnessed by the Engineer of Record is the hold point most water and wastewater projects with a resident engineer use, a Contractor self-inspection with a signed report is the practice where the Owner's inspector is not resident and the Contractor's foreman is experienced, and an independent inspector is retained where the Owner's insurer or the Authority Having Jurisdiction requires it or the facility is unattended. The choice follows the project's inspection staffing, and no option is distinctly the norm, so the field carries no default. {note}
+
+### The inspection shall verify, and the report shall record, each of the following:
+
+- Every seal on the seal schedule is installed, poured after its conductors, dated, and visibly complete
+- Every box, fitting, enclosure and item of equipment within the location is listed for the class, division or zone, group, and temperature code shown on the classification drawings, by comparing the nameplate to the listing schedule
+- Every explosionproof cover is in place and bolted, every unused opening is plugged, and every threaded joint is made up with the required engagement
+- Every intrinsically safe loop matches its control drawing, its separation is as selected in the datasheet, its identification is in place, and the intrinsically safe ground bus resistance has been measured
+- Every purged and pressurized enclosure has been purged, holds its pressure, and alarms or de-energizes on loss of pressure as its type requires
+- Every bonding jumper and bonding fitting between the location and the source is in place
+- Every drain seal and breather is installed at a low point and oriented as listed
+- Where a classification depends on ventilation, the ventilation is operating and its failure alarm has been proven
+- Where combustible gas detection is applied as a protection technique, the interlock operates at the documented concentration
+
+### The Contractor shall correct every deficiency the inspection finds and shall re-inspect the corrected item, at the Contractor's expense, before the circuit is energized.
+
+### The Contractor shall give the inspecting party not less than five working days' notice of the inspection, and shall not close any explosionproof enclosure, pour any seal, or energize any circuit in the location before the inspection it is subject to has been completed, except that seals may be poured before the inspection where the inspecting party has approved the pour in writing on the seal schedule.
+
+## Record of Classified Areas {toc}
+
+### The record of classified areas delivered at closeout shall be in the format indicated in the datasheet, and shall reflect every source, boundary, and ventilation dependency as built.
+
+```datasheet
+label: Closeout Record of Classified Areas
+type: select
+options:
+ - "Record hazardous area classification drawings"
+ - "Record drawings and a tabular register of classified areas"
+ - "Record drawings, a register, and the listing schedule of equipment in each area"
+default: "Record hazardous area classification drawings"
+```
+
+### The record set of the classification drawings, marked for every change made during construction, is the documentation NFPA 70 500.4(A) requires the Owner to keep available, and is the closeout record of most projects, which is why it is the default. A tabular register adds, for each area, its class, division or zone, group, temperature code, basis document, and the ventilation it depends on, in a form an operator can read without the drawings, and is chosen where the facility has an electrical safety program that maintains such a register. Adding the listing schedule gives the Owner the record of what is installed in each area, which is what a future modification or a replacement device is checked against, and is chosen where the Owner's maintenance staff will make those changes without an engineer. {note}
+
+### The Contractor shall deliver the record of classified areas to the Owner as a closeout submittal, and the Engineer of Record shall certify the record classification drawings as the classification of record.
+
+### The record of classified areas stays with the Owner, and every later change to a source, a boundary, a ventilation system, or an item of equipment in a classified area is checked against it; a classification that lives only in the design file is unavailable to the electrician who replaces a level switch in ten years. {note}
+
+# Delivery, Storage, and Handling {toc}
+
+## Explosionproof and dust-ignitionproof enclosures, boxes, fittings and sealing fittings shall be delivered with their covers in place, their threaded entries plugged, and their flame-path surfaces protected by the manufacturer's packaging, and shall be stored indoors off the floor until installed.
+
+## Sealing compound and fiber dam material shall be stored in the manufacturer's sealed containers within the temperature range the manufacturer states, and compound that has been exposed to moisture or has exceeded its shelf life shall not be used.
+
+## PVC-coated conduit and fittings shall be handled so that the coating is not cut or abraded, and shall be installed with strap wrenches and the manufacturer's tools; coating damage shall be repaired with the manufacturer's patching compound before the conduit is installed.
+
+## Equipment and fittings whose flame-path surfaces, threads, or coatings are damaged in shipping, storage or handling shall be removed from the project and replaced at the Contractor's expense.
+
+# Warranty {toc}
+
+## The Contractor's installation warranty period shall be as indicated in the datasheet.
+
+```datasheet
+label: Installation Warranty Period
+type: select
+options:
+ - "1 year from substantial completion"
+ - "2 years from substantial completion"
+ - "5 years from substantial completion"
+default: "1 year from substantial completion"
+```
+
+## One year from substantial completion is the installation warranty of nearly every public-works electrical contract and is the default; a 2 year term is chosen where the Owner's general conditions extend every trade to it, and a 5 year term where the Owner buys a long warranty on the sealed and concealed work of a wet well or a digester gallery that cannot be re-inspected without a confined space entry, at a price the bidders carry in the installation. {note}
+
+## The Contractor shall warrant the installation within and at the boundary of every classified location, including the seals, the raceway and fitting system, the bonding, the identification, and the purge and pressurization systems furnished under this standard, for the warranty period indicated in the datasheet.
+
+## Equipment and fittings shall carry the manufacturer's published product warranty against defects in materials; the Contractor's installation warranty does not relieve the manufacturer of product warranty obligations.
+
+## Warranty corrective work within a classified location shall be performed with the location de-energized or under the protection technique the installation requires, shall include re-inspection of the corrected item as the Classified-Location Inspection article requires, and shall include repair of finishes and other work disturbed by the repair, at the Contractor's expense.
+
+## A seal, a fitting, or an enclosure replaced under warranty shall be warranted for the remainder of the original warranty period or 12 months from completion of the repair, whichever is longer.
+
+## Where the parties disagree whether a warranty-period failure results from workmanship, a product defect, or a change the Owner made to a source, a boundary, or the ventilation after acceptance, the Engineer of Record shall make the initial determination.