1 Scope
NOTE This standard covers the design documentation, agent selection, equipment, installation, testing, and commissioning of gaseous total-flooding clean-agent fire extinguishing systems installed to protect an enclosed volume by establishing and holding a uniform extinguishing concentration of a clean agent throughout that volume. (1.1)
NOTE A clean agent is defined by NFPA 2001, Standard on Clean Agent Fire Extinguishing Systems, as an electrically non-conductive, volatile or gaseous fire extinguishant that does not leave a residue upon evaporation. (1.2)
NOTE The defining advantage of these systems is that they suppress fire without water, foam, or powder, so they protect energized electronic equipment, irreplaceable records, and sensitive contents that water-based suppression would destroy. (1.3)
NOTE A total-flooding clean-agent system does not act on a single burning object the way a sprinkler discharges onto a fire; it floods the entire protected enclosure to a design concentration and then relies on the enclosure to hold that concentration long enough for the fire to be fully extinguished and for hot surfaces to cool below the point of re-ignition. For this reason the integrity of the enclosure is as much a part of the system as the agent and the hardware, and an enclosure that leaks the agent faster than the design hold time allows is a defective installation even if every container, pipe, and nozzle is perfect. (1.4)
1.5The enclosure-integrity (door-fan) test required by NFPA 2001 is a mandatory part of the work under this standard, not an optional extra.
NOTE The scope extends from the agent storage containers and their actuation devices, through the discharge piping and nozzles, to the protected enclosure and its pressure-relief venting; and it includes the dedicated detection and releasing control unit, the cross-zoned detection, the manual release and abort stations, the discharge and pre-discharge alarms and warning signs, and the interlocks to the building HVAC and dampers that condition the enclosure for a successful discharge. (1.6)
1.7All work shall comply with NFPA 2001 for the clean-agent system itself, with NFPA 72, National Fire Alarm and Signaling Code, for the detection and releasing service that actuates it, and with NFPA 70, National Electrical Code, for the wiring.
1.8The agent shall be one that is acceptable for total-flooding use under the U.S. EPA Significant New Alternatives Policy (SNAP) program for the occupancy condition involved.
1.9Agents shall be described by their NFPA 2001 generic designation (for example HFC-227ea, FK-5-1-12, IG-541, IG-55, IG-100) and never by trademarked brand name.
NOTE This standard establishes the performance, safety, and quality requirements that the designer's agent and listed-system selection shall satisfy. (1.10)
2 Referenced Standards
2.1Design, equipment, installation, and testing shall comply with the current adopted editions of the following standards and codes.
| Standard |
Title |
| NFPA 2001 |
Standard on Clean Agent Fire Extinguishing Systems |
| NFPA 72 |
National Fire Alarm and Signaling Code (detection and releasing service) |
| NFPA 70 |
National Electrical Code |
| NFPA 70B |
Standard for Electrical Equipment Maintenance (where electrical rooms are protected) |
| NFPA 75 |
Standard for the Fire Protection of Information Technology Equipment |
| NFPA 76 |
Standard for the Fire Protection of Telecommunications Facilities |
| NFPA 12 |
Standard on Carbon Dioxide Extinguishing Systems (referenced for distinction; CO2 is outside this scope) |
| UL 2166 |
Standard for Halocarbon Clean Agent Extinguishing System Units |
| UL 2127 |
Standard for Inert Gas Clean Agent Extinguishing System Units |
| UL 864 |
Standard for Control Units and Accessories for Fire Alarm Systems (releasing service) |
| UL 268 |
Standard for Smoke Detectors for Fire Alarm Systems |
| ISO 14520 |
Gaseous Fire-Extinguishing Systems — Physical Properties and System Design |
| FM Approval Standards (3500-series) |
Approval standards for clean-agent extinguishing systems |
| EPA SNAP |
U.S. EPA Significant New Alternatives Policy program (agent acceptability) |
| ASME Boiler and Pressure Vessel Code, Sec. VIII |
Rules for the construction of pressure vessels (agent storage containers) |
| DOT 49 CFR |
Transportation of agent containers as compressed gas / hazardous materials |
| IBC |
International Building Code |
| IFC |
International Fire Code |
2.2Where the contract documents, the adopted building or fire code, a listed-system manufacturer's design and installation manual, or a referenced standard conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
2.3A clean-agent system is a listed assembly: the listed-system design and installation manual establishes container fill ranges, pipe limits, and nozzle coverage that are conditions of the listing and shall not be exceeded even where this standard or the drawings would otherwise permit it.
3 Submittals
3.1 Action Submittals
3.1.1The Contractor shall submit the following for the Engineer of Record's review and the Authority Having Jurisdiction's approval before any agent containers are procured or any portion of the system is installed:
- Working drawings showing the protected enclosure(s), the agent storage location, the routing and size of all discharge piping, the type and location of every nozzle, the location of every detector, manual release, abort station, alarm, and warning sign, and the location of the releasing control unit
- Design concentration calculations establishing the minimum design concentration for the agent and the hazard (flooding factor, the volume of the enclosure, the design temperature, and the resulting agent quantity), with the basis (Class A surface fire, Class B fuel, or energized-equipment design factor) clearly stated and referenced to NFPA 2001
- Flow (hydraulic) calculations from the listed-system manufacturer's design software, demonstrating that the piping network delivers the required agent quantity to each nozzle and reaches 95 percent of the minimum design concentration within the maximum discharge time permitted by NFPA 2001 for the agent family
- Occupant-safety analysis stating, for the agent and design concentration selected, the NOAEL and LOAEL (for halocarbon agents) or the resulting minimum oxygen concentration (for inert-gas agents), the occupancy classification of the protected space (normally occupied or normally unoccupied), and the maximum permitted occupant exposure time, in accordance with NFPA 2001
- An enclosure-integrity analysis predicting the agent retention (hold) time for the as-designed enclosure, identifying all known and suspected leakage paths, and committing to a door-fan test at acceptance to verify the predicted hold time
- Sequence of operations (matrix) showing every detection input (by zone), the cross-zoning logic, the pre-discharge alarm, the time delay, the abort logic, the discharge output, and every interlock and ancillary function (HVAC and fan shutdown, damper closure, door closure/holders, power shutdown where applicable)
- Battery (secondary-power) calculations for the releasing control unit per NFPA 72, showing standby and alarm current and the required amp-hour capacity with the code-required margin
- Product data and listing documentation for the agent, the storage containers and valves, the discharge nozzles, the releasing control unit (UL 864 listed for releasing service), the detectors, and the manual release and abort stations, including the UL 2166 (halocarbon) or UL 2127 (inert-gas) system listing and the EPA SNAP acceptability of the agent for the occupancy condition
☐ Working drawings (enclosure, piping, nozzles, devices, control unit)
☐ Design concentration calculations
☐ Flow (hydraulic) calculations from listed design software
☐ Occupant-safety analysis (NOAEL/LOAEL or minimum O2)
☐ Enclosure-integrity analysis and committed hold time
☐ Sequence of operations matrix
☐ Releasing control unit battery calculations (NFPA 72)
☐ Product data and listing documentation (UL 2166 / UL 2127, EPA SNAP)
3.1.2The clean-agent calculations and the enclosure analysis are the heart of the submittal and shall be complete, sealed where required by state law, and internally coordinated before the package is submitted.
3.2 Closeout Submittals
3.2.1The following shall be submitted at substantial completion, before the system is placed in service and accepted:
- Signed acceptance test report documenting the detection, releasing, alarm, abort, and interlock functions verified per NFPA 2001 and NFPA 72, including the verified pre-discharge delay and the verified ancillary shutdowns
- The enclosure-integrity (door-fan) test report, recording the measured enclosure leakage, the calculated agent retention (hold) time at the design concentration descending to the protected height, and the pass/fail determination against the required minimum hold time
- As-built working drawings reflecting actual piping routing and sizes, nozzle locations, device locations, and the final container fill weights or pressures
- The releasing control unit programming record, including the cross-zoning logic, the time delay, and the abort behavior as commissioned
- Operation and maintenance data, including the agent type and quantity per container, the container recharge and hydrostatic-retest schedule, the detector and control-unit inspection and test intervals per NFPA 2001 and NFPA 72, and the date by which the next enclosure-integrity test is recommended
- Warning and instruction signs verification (pre-discharge, discharge, abort, and lockout/disable signage installed at the required locations)
☐ Acceptance test report (detection, release, alarm, abort, interlocks)
☐ Enclosure-integrity (door-fan) test report with hold time
☐ As-built working drawings with final fill weights/pressures
☐ Releasing control unit programming record
☐ Operation and maintenance data
☐ Warning and instruction signage verification
4 Quality Assurance
4.1 Designer and Installer Qualifications
NOTE The listed clean-agent system is an engineered assembly whose flow calculations, container fill ranges, pipe-length and fitting limits, and nozzle coverage are valid only when the system is designed using the manufacturer's listed design software and installed within the limits of the manufacturer's design and installation manual. (4.1.1)
○ Manufacturer-certified designer/installer for the listed system + state license
○ Licensed fire protection engineer (special hazards) + manufacturer-certified installer
○ NICET special-hazards / clean-agent certification + state license
○ As accepted by AHJ — submit documentation for review
4.1.2The clean-agent system shall be designed, installed, and commissioned by personnel trained and certified by the manufacturer of the listed system being installed, in accordance with NFPA 2001.
4.1.3The Contractor shall hold the licensing required by the state and local jurisdiction for fire suppression system work.
4.1.4The individual preparing the design shall hold the qualifications the AHJ requires (commonly a licensed fire protection engineer or a NICET-certified designer in special-hazards or clean-agent systems at the level required by state law).
4.2 Listing and Approval
○ UL 2166 (halocarbon) listed system throughout
○ UL 2127 (inert gas) listed system throughout
○ ISO 14520 designed with FM approval
○ UL listing plus FM approval (insurer requirement)
4.2.1The complete clean-agent system shall be a listed system — agent, containers, valves, actuators, nozzles, pipe limits, and the releasing control unit evaluated together — listed to UL 2166 for halocarbon agents or to UL 2127 for inert-gas agents, or to the equivalent ISO 14520 and FM approval where the project requires it.
4.2.2Components shall not be mixed across listings; a nozzle, container valve, or quantity outside the listed system invalidates the flow calculation and the listing.
4.2.3The releasing control unit shall be listed to UL 864 for releasing service.
4.2.4The agent shall be acceptable for total-flooding use under the EPA SNAP program for the occupancy condition (normally occupied or normally unoccupied) involved.
4.3 Coordination with Other Trades
NOTE The enclosure that holds the agent is built by other trades: every cable penetration, conduit sleeve, raised-floor and ceiling-plenum boundary, door undercut, damper, and duct opening is a potential leakage path that determines whether the system passes its enclosure-integrity test. (4.3.1)
4.3.2The clean-agent Contractor shall coordinate early and continuously with the mechanical, electrical, architectural, and fire alarm trades.
4.3.3The Contractor shall identify the enclosure boundary on the working drawings.
4.3.4The Contractor shall coordinate sealing of all penetrations with the trades that create them.
4.3.5The Contractor shall coordinate the shutdown of HVAC and the closure of dampers and doors on discharge with the mechanical and fire alarm contractors.
5 Environmental and Service Conditions
5.1 Storage and Discharge Temperature
5.1.1Halocarbon agents are stored as a liquid under superpressurization with an inert gas (commonly nitrogen); the storage temperature affects the container pressure and the quantity of agent that can be discharged through the piping, and the design temperature of the protected space affects the volume the agent must flood and therefore the required quantity.
NOTE Inert-gas agents are stored as a high-pressure gas and are likewise temperature sensitive. (5.1.2)
0130
324070100130
Default: 70 °F
0100
32507090100
Default: 70 °F
5.1.3The agent storage containers and the protected enclosure shall be within the temperature range for which the listed system is rated.
NOTE The minimum design temperature of the enclosure governs the agent quantity, because a colder, denser atmosphere requires more agent to reach the design concentration. (5.1.4)
6 System Type and Agent Selection
6.1 Total-Flooding Basis
6.1.1The system shall be a total-flooding system that establishes a uniform agent concentration throughout the protected volume.
6.1.2Local-application clean-agent systems are not within this scope.
6.1.3The protected volume is the gross enclosure volume, including any raised-floor void and ceiling plenum that is part of the protected space and is not otherwise sealed off.
6.1.4Where the void or plenum is a separate fire risk (containing power or data cabling), it shall be protected and the agent quantity calculated for it as part of the design.
6.2 Agent Family
NOTE The two agent families differ fundamentally in how they extinguish fire, in how much agent is required, in their occupant-safety behavior, and in their discharge and venting requirements, and the choice drives the rest of the design. (6.2.1)
○ Halocarbon (heat-absorbing; liquid storage; 10 s discharge)
○ Inert gas (oxygen-reducing; high-pressure gas storage; 60 s discharge)
HFC-227ea (halocarbon)
FK-5-1-12 fluoroketone (halocarbon)
IG-541 — nitrogen/argon/CO2 (inert gas)
IG-55 — nitrogen/argon (inert gas)
IG-100 — nitrogen (inert gas)
NOTE Halocarbon agents (for example HFC-227ea and the fluoroketone FK-5-1-12) extinguish primarily by absorbing heat from the flame; they are stored as a liquid, require a relatively small storage footprint, flood the space quickly, and are subject to a maximum 10-second discharge time. (6.2.2)
NOTE Inert-gas agents (for example IG-541, a blend of nitrogen, argon, and carbon dioxide; IG-55, a nitrogen-argon blend; and IG-100, nitrogen) extinguish by displacing oxygen and reducing it below the level that supports combustion; they are stored as a high-pressure gas, require a substantially larger bank of cylinders, discharge over a longer 60-second period, and demand careful pressure-relief venting because they add a large gas volume to the enclosure. (6.2.3)
6.2.4The agent shall be selected for the hazard, the occupancy condition, the available storage space, the enclosure's ability to tolerate the over- and under-pressure of discharge, and the Owner's environmental objectives.
6.2.5The Contractor shall not substitute a different agent or agent family after design approval without re-running the design concentration, occupant-safety, flow, and enclosure-integrity analyses and resubmitting them, because the agents are not interchangeable.
7 Design Concentration and Occupant Safety
7.1 Minimum Design Concentration
NOTE The minimum design concentration is derived from the agent's measured extinguishing concentration with a safety factor applied: for Class A surface fires the design concentration is based on the agent's listed Class A extinguishing concentration (established through the UL 2166 or UL 2127 listing program) with the NFPA 2001 safety factor; for Class B fuels it is the cup-burner extinguishing concentration multiplied by the NFPA 2001 safety factor (1.3 for Class B). (7.1.1)
NOTE Where the protected hazard is energized electronic or electrical equipment, an additional design factor is applied per NFPA 2001 to account for the deeper-seated nature of such fires. (7.1.2)
○ Class A surface fire (electronic / records / general contents)
○ Class A energized-equipment hazard (added NFPA 2001 design factor)
○ Class B fuel (cup-burner concentration × 1.3)
512
567891012
Default: 7 % by volume
3452
343740434852
Default: 40 % by volume
7.1.3The agent quantity shall be calculated to establish at least the minimum design concentration throughout the protected volume at the minimum enclosure design temperature, in accordance with NFPA 2001.
7.1.4The design concentration and its basis shall be stated on the calculations and shall be the more demanding where multiple fire types are present.
7.2 Occupancy and the NOAEL / LOAEL Safety Margin
7.2.1The occupant-safety requirements of NFPA 2001 govern whether the design concentration is acceptable in the protected space and how long occupants may be exposed.
○ Normally occupied — design concentration at or below NOAEL / safe O2 level
○ Normally unoccupied — egress provisions before discharge
NOTE For halocarbon agents, safety is expressed by the NOAEL (no observed adverse effect level — the highest concentration at which no adverse physiological effect was observed) and the LOAEL (lowest observed adverse effect level — the lowest concentration at which an adverse effect was observed). (7.2.2)
7.2.3In a normally occupied space the design concentration shall not exceed the agent's NOAEL.
7.2.4Where the halocarbon design concentration falls between the NOAEL and the LOAEL, occupancy and exposure time shall be limited per NFPA 2001.
7.2.5Halocarbon concentrations above the LOAEL are permitted only in normally unoccupied spaces with provisions for occupant egress before discharge.
7.2.6As a reference point, HFC-227ea has a NOAEL of 9.0 percent and a LOAEL of 10.5 percent by volume; the designer shall use the values for the specific agent from the current NFPA 2001 tables.
NOTE For inert-gas agents, occupant safety is governed by the resulting oxygen concentration rather than agent toxicity: reducing oxygen to no lower than about 12 percent (an inert-gas concentration up to roughly 43 percent) permits a limited occupied-exposure period, lower oxygen levels (higher inert-gas concentrations) progressively shorten the permitted exposure, and below about 10 percent oxygen exposure is permitted only in normally unoccupied spaces with controlled egress, in accordance with NFPA 2001. (7.2.7)
7.2.8The egress time built into the pre-discharge sequence shall be reconciled with the permitted exposure time for the design concentration so that occupants can clear the space before a hazardous condition exists.
8 Detection and Releasing Control
8.1 Releasing Control Unit
NOTE The releasing unit continuously supervises the detection, the actuation circuits, the manual release and abort stations, and the agent-container and pressure-supervisory devices; processes the detection logic; provides the pre-discharge delay and abort; and energizes the actuator that releases the agent. (8.1.1)
○ UL 864 listed for releasing service
8.1.2The system shall be actuated by a dedicated releasing control unit listed to UL 864 for releasing service, in accordance with NFPA 72 and NFPA 2001.
NOTE The releasing function is distinct from the building fire alarm system: the releasing unit transmits alarm, supervisory, and trouble signals to the building fire alarm system and the supervising station for occupant notification and off-premises reporting (see
Fire Alarm Systems), but the agent release decision is made by the dedicated releasing unit.
(8.1.3) 8.2 Cross-Zoned Detection
NOTE Cross-zoning prevents an extremely costly and disruptive accidental discharge from one faulty or transiently triggered detector while still providing fast response when a real fire is confirmed by detectors on two separate zones. (8.2.1)
○ Cross-zoned — two independent detection zones required to release (standard)
○ Counting zone — two detectors on one engineered zone required to release
Spot-type smoke detectors (UL 268), cross-zoned at ceiling
Spot-type smoke detectors at ceiling, floor void, and ceiling plenum
Air-sampling (aspirating) detection for early warning
Air-sampling at room plus spot-type in voids
8.2.2Automatic actuation shall require two independent detection inputs in alarm before the discharge sequence begins — a cross-zoned (or counting-zone) detection arrangement — so that a single detector in alarm cannot by itself release the agent.
8.2.3Detectors shall be spot-type smoke detectors listed to UL 268, or aspirating (air-sampling) detection where early-warning sensitivity is required, located and spaced per NFPA 72 with the spacing reduced as required for the air movement in the protected space.
8.2.4Where the enclosure has a raised-floor void or a ceiling plenum that is part of the protected volume, detection shall be provided in those concealed spaces as well as at the ceiling.
8.3 Pre-Discharge Alarm, Time Delay, and Abort
NOTE The time delay allows occupants to evacuate and allows an abort if the alarm is investigated and found not to warrant discharge. (8.3.1)
☐ Manual release (electric, at egress) — overrides time delay
☐ Manual abort (dead-man, constant pressure) — holds discharge during delay
☐ Maintenance lockout / disable switch with supervised trouble signal
8.3.2On confirmation of the cross-zoned alarm, the system shall sound a distinct pre-discharge alarm, activate warning signs and strobes at the entrances to and inside the protected space, initiate the ancillary shutdowns (HVAC and fan shutdown, damper and door closure), and begin a time delay before discharge.
8.3.3The time delay shall be long enough for occupant egress yet short enough that fire growth does not exceed what the design concentration can extinguish, and shall not exceed the limit established by NFPA 2001 for the occupancy.
8.3.4A manual abort station, where provided, shall require constant manual pressure to hold the discharge in abort and shall not defeat the manual release.
8.3.5Releasing the abort or operating the manual release shall allow or cause discharge.
8.3.6The abort shall not silence the pre-discharge alarm and shall be of the "dead-man" type so that the system cannot be left indefinitely disabled by a jammed or taped abort.
8.3.7A manual release station shall be provided at the means of egress from the protected space to allow a person to discharge the system immediately, overriding the time delay.
8.4 Ancillary Functions and Interlocks
8.4.1The releasing sequence shall shut down or reconfigure the equipment that would otherwise prevent the enclosure from holding the agent.
☐ HVAC / air-handler shutdown serving the enclosure
☐ Supply / return / exhaust damper closure at enclosure boundary
☐ Door holder release / self-closing door closure
☐ Equipment power shutdown (only where intended)
☐ Signal to building fire alarm system and supervising station
8.4.2Heating, ventilating, and air-conditioning units serving or communicating with the protected space shall be shut down, and dampers in the supply, return, and exhaust ducts crossing the enclosure boundary shall close, before or at the moment of discharge, so that the agent is not swept out of the enclosure.
8.4.3Self-closing doors and any doors held open by electromagnetic holders shall release and close.
8.4.4Where the protected hazard requires it and is permitted, electrical power to the protected equipment may be shut down on discharge; this interlock shall be applied only where intended, because cutting power to equipment can itself cause an unacceptable loss.
9 Agent Storage and Distribution
9.1 Storage Containers
NOTE Halocarbon containers store the agent as a superpressurized liquid; inert-gas containers store the agent as a high-pressure gas, typically in a multi-cylinder bank with a manifold. (9.1.1)
○ Single container (small halocarbon enclosure)
○ Multiple containers, common manifold (large or multi-zone)
○ Multi-cylinder high-pressure bank with manifold (inert gas)
☐ Low-pressure supervisory switch (signals loss of pressure)
☐ Liquid-level / weight monitoring (halocarbon)
☐ Manifold pressure gauge
9.1.2Agent shall be stored in listed containers that are part of the listed system, located as close as practicable to the protected enclosure to keep pipe runs within the listed limits.
9.1.3Containers shall be located where they are accessible for inspection, weighing or pressure checking, maintenance, and recharge.
9.1.4Containers shall be secured against movement and the reaction forces of discharge, protected from physical damage and from temperatures outside their listed range, and provided with the pressure gauge or liquid-level indicating means required for routine inspection.
9.1.5Containers are pressure vessels and shall carry the markings and the hydrostatic-retest currency required by NFPA 2001 and DOT.
9.1.6Each container shall be monitored by a low-pressure supervisory switch (and, for halocarbon agents, by a means of detecting loss of agent quantity such as weight or liquid level) that transmits a supervisory signal to the releasing control unit.
NOTE A container that has slowly lost agent or pressure without anyone knowing is one of the most dangerous latent failures of a clean-agent system, because the system appears intact but cannot reach the design concentration. (9.1.7)
9.2 Discharge Piping and Fittings
NOTE The pipe network is part of the listed system and the flow calculation governs whether each nozzle delivers its share of agent within the discharge time. (9.2.1)
○ Per listed-system flow calculation — size, schedule, layout, and fittings as calculated
○ Balanced (symmetrical) network
○ Unbalanced network per listed flow calculation
9.2.2Discharge piping shall be the type and schedule required by the listed system and by NFPA 2001, sized and arranged exactly as the manufacturer's flow calculation requires.
9.2.3The pipe network shall not deviate from the calculated layout in length, size, fitting count, or tee orientation.
9.2.4Piping shall be reamed and blown clear of cuttings and debris before assembly.
9.2.5Pipe and fittings shall be rated for the maximum pressure developed on discharge, which for inert-gas systems is high and is established by the listed system.
9.2.6Piping shall be supported to resist the substantial reaction and thrust forces produced at tees, elbows, and nozzles during the rapid discharge.
9.3 Nozzles
○ Per listed nozzle coverage and height limits (type and orifice per flow calc)
☐ Room (above raised floor, below ceiling)
☐ Raised-floor void
☐ Ceiling plenum
9.3.1Discharge nozzles shall be the type, orifice, and quantity established by the flow calculation and shall be installed at the locations, heights, and orientations shown on the working drawings so that the agent disperses uniformly and reaches the design concentration throughout the protected volume within the discharge time.
9.3.2Nozzle coverage area and height limits are conditions of the listing and shall not be exceeded.
9.3.3Nozzles shall be oriented to avoid blowing directly on light, loose contents that the high-velocity discharge could disturb, and shall be kept clear of obstructions.
9.3.4Where the raised-floor void or ceiling plenum is part of the protected volume, nozzles shall be provided in those spaces.
9.4 Discharge Time
NOTE The discharge time is fixed by the agent family and is a pass/fail requirement of NFPA 2001. (9.4.1)
30120
306090120
Default: 60 s
9.4.2For halocarbon agents the system shall deliver at least 95 percent of the minimum design concentration within 10 seconds, because a halocarbon agent must reach concentration quickly to absorb heat before the fire grows and before agent decomposition products (such as hydrogen fluoride) accumulate.
9.4.3For inert-gas agents the discharge time is longer — typically not more than 60 seconds to reach the design concentration — because the agent extinguishes by oxygen displacement and a slower fill limits the over-pressure imposed on the enclosure as a large volume of gas is added.
9.4.4The flow calculation shall demonstrate compliance with the discharge time for the agent family.
10 Enclosure Integrity
10.1 Hold (Soak) Time and Leakage
NOTE Establishing the concentration is not enough; the fire is extinguished and hot surfaces cool over the hold period, and if the agent leaks away too quickly through unsealed penetrations, door undercuts, dampers that did not close, or a porous boundary, the fire can re-ignite. (10.1.1)
530
510152030
Default: 10 min
10.1.2The enclosure shall retain the agent at or above the concentration needed to prevent re-ignition for a minimum hold (soak) time after discharge, in accordance with NFPA 2001.
10.1.3The required hold time is commonly 10 minutes unless a different value is justified by the time the hazard will go unattended after discharge.
10.1.4The enclosure boundary shall be made substantially tight: cable and conduit penetrations sealed, dampers arranged to close on discharge, doors self-closing and reasonably gasketed, and the floor void and ceiling plenum boundaries sealed where they form part of the enclosure.
10.2 Door-Fan (Enclosure-Integrity) Test
NOTE A calibrated fan mounted in a doorway pressurizes and depressurizes the enclosure while measuring the airflow required to hold a series of pressures; from the measured leakage and the enclosure geometry the test calculates the predicted agent retention (hold) time at the design concentration descending to the protected height. (10.2.1)
NOTE This test substitutes for an actual agent discharge — it is impractical and wasteful to verify hold time by discharging agent — and it locates leakage paths so they can be sealed. (10.2.2)
○ Door-fan test per NFPA 2001 — predicted hold time meets or exceeds required hold time
10.2.3The enclosure integrity shall be verified by a door-fan (enclosure-integrity) test performed in accordance with the procedure in NFPA 2001, both as a design tool and at acceptance.
10.2.4The system shall not be accepted until the door-fan test demonstrates that the enclosure will hold the agent for at least the required hold time.
10.2.5Where the test fails, the leakage paths shall be sealed and the test repeated until it passes.
11 Pressure Relief Venting
NOTE The discharge of agent changes the enclosure pressure: a halocarbon discharge can cause both a brief negative excursion (as cold liquid vaporizes) and a positive excursion, while an inert-gas discharge adds a large volume of gas that produces a sustained positive over-pressure. (11.1)
NOTE A modern, tightly sealed enclosure — exactly the kind that holds the agent well — cannot relieve this pressure through incidental leakage and can have its walls, ceiling, or floor structurally over-stressed unless a pressure-relief vent is provided. (11.2)
○ Pressure relief vent sized per NFPA 2001 for agent quantity and enclosure strength
○ Engineering analysis confirms enclosure leakage adequate — no added vent (rare; documented)
Barometric (self-closing) relief damper
Motorized relief damper interlocked to discharge
Per drawings
550
510152550
Default: 10 lb/ft²
11.3The protected enclosure shall be provided with pressure relief sized for the agent and the discharge so that the enclosure structure is not damaged by the pressure transient of discharge, in accordance with NFPA 2001.
11.4The relief vent shall be sized from the agent quantity and discharge rate and the enclosure's allowable pressure.
11.5The relief vent shall be a listed barometric or motorized damper-type relief that opens during discharge and otherwise stays closed so it does not itself become a leakage path that shortens the hold time.
12 Testing and Commissioning
12.1 Acceptance Test
12.1.1The complete system shall be tested and commissioned at acceptance in accordance with NFPA 2001 and NFPA 72, with the AHJ witnessing where required.
☐ Cross-zoned detection logic verified
☐ Pre-discharge alarm, signs, and strobes verified
☐ Time delay duration verified
☐ Manual release and abort behavior verified
☐ Circuit supervision (detection, actuation, container pressure) verified
☐ Ancillary functions (HVAC, dampers, doors, power) verified
☐ Signal to fire alarm system / supervising station verified
☐ Actuation verified without agent discharge
12.1.2The acceptance test shall verify the detection and its cross-zoning logic; the pre-discharge alarm and warning signs; the time delay and its duration; the manual release and the abort behavior; the supervision of the detection, actuation, and container-pressure circuits; the transmission of alarm, supervisory, and trouble signals to the building fire alarm system; and every ancillary function (HVAC and fan shutdown, damper and door closure, and any power shutdown).
12.1.3The actuation circuit shall be verified without discharging agent by substituting a means that confirms the actuator would fire, in accordance with the manufacturer's instructions.
12.1.4Agent shall not be discharged for acceptance unless specifically required and accepted.
12.2 Enclosure-Integrity Test at Acceptance
12.2.1The door-fan test shall be performed at acceptance after all penetrations are sealed and the enclosure is in its final, in-service condition, and the predicted hold time shall meet or exceed the required hold time before the system is accepted.
12.2.2The test result shall be recorded in the closeout documents and shall establish the baseline against which future periodic enclosure-integrity tests are compared, since enclosure tightness degrades over time as cables are added and penetrations are opened.
13 Installation
13.1 General
13.1.1The Contractor shall install the system in accordance with this standard, the approved working drawings, NFPA 2001, NFPA 72, NFPA 70, and the listed-system manufacturer's design and installation manual.
13.1.2Where these conflict, the more stringent governs, and no installation shall deviate from the conditions of the listing.
13.1.3Piping shall be installed to the calculated layout, reamed and cleaned, pressure-tight, and supported to resist discharge reaction forces.
13.1.4Nozzles shall be installed at the locations and orientations shown.
13.1.5Detection, manual stations, alarms, and signs shall be installed at the heights and locations required for visibility and reach.
13.2 Signage
☐ Entrance: clean-agent protection / evacuate on alarm
☐ Manual release station identification
☐ Abort station identification and limits
☐ Lockout / disable (out-of-service) sign
☐ Agent storage room identification
13.2.1Warning and instruction signs shall be provided in accordance with NFPA 2001 at the entrances to and inside the protected space and at the agent storage and control locations: a sign warning that the space is protected by a clean-agent system and that occupants shall evacuate on the pre-discharge alarm; a sign at the manual release identifying its function; a sign at the abort identifying its function and limits; and a sign at any lockout/disable switch.
13.2.2Signs shall be permanent and legible.
14 Delivery, Storage, and Handling
○ Factory-charged, marked with agent type/quantity and fill weight or pressure, retest current
14.1Agent containers shall be delivered fully charged, with the agent type and quantity and the charge pressure or fill weight marked on each container, and with the actuation devices secured for transport.
14.2Containers shall be kept capped, secured upright or as the manufacturer requires, and protected from physical damage and from temperatures outside their listed range until installed.
14.3Containers are pressure vessels transported under DOT rules; the Contractor shall verify the hydrostatic-retest currency of each container on receipt and shall not install a container whose retest is out of date.
14.4Actuation devices (electric, pneumatic, or cartridge actuators) shall be kept disconnected or secured so that the system cannot discharge during handling and installation, and shall be connected and armed only as the final commissioning step after the detection and control system have been verified.
15 Warranty
15.1The Contractor shall warrant the clean-agent system installation against defects in materials and workmanship for a period of not less than one year from substantial completion, or for the period stated in the contract documents if longer.
15.2Any defect in the detection, releasing, actuation, piping, or nozzles, and any failure of the enclosure-integrity provisions installed under this scope that causes the system to fail to reach or hold the design concentration, shall be corrected at the Contractor's expense, including the cost of recharging agent expended in correcting the defect.
15.3Correction of a deficiency that requires re-sealing the enclosure and re-running the door-fan test shall be performed and re-verified at the Contractor's expense.
16 Spare Parts
16.1The Contractor shall provide the spare components recommended by the listed-system manufacturer for maintaining the system in service without delay, in accordance with NFPA 2001 and the contract documents.
16.2As a minimum, the Contractor shall provide the following:
- Spare detectors of each type installed
- The means (a spare or rechargeable container arrangement) by which the system can be returned to service after a discharge with minimum downtime
☐ Spare detector(s) of each installed type
☐ Spare actuation device(s)
☐ Agent recharge source identified for prompt return to service
☐ Container hydrostatic-retest schedule provided to Owner
NOTE A discharged system leaves the protected space unprotected until the agent is recharged. (16.3)
16.4The Owner shall be advised of the agent recharge source and the container hydrostatic-retest schedule so the system is maintained ready throughout its life.