1 Scope
NOTE This standard governs the design, materials, fabrication, installation, testing, and verification of piped medical gas and vacuum systems serving patient care areas in healthcare facilities. (1.1)
NOTE Medical gas and vacuum systems are life-safety systems: a source failure, cross-connection, or contaminated gas can cause patient death. NFPA 99 therefore treats these systems with the same rigor as fire protection, imposing redundant sources, independent verification, and qualified personnel at every stage. (1.2)
NOTE The system Category (1, 2, or 3) determined under NFPA 99 Chapter 4 drives nearly every other requirement in this standard and shall be established before design begins. (1.3)
1.3.1Work governed by this standard shall comply with NFPA 99 for the edition adopted by the authority having jurisdiction.
1.3.2The Contractor shall confirm the adopted NFPA 99 edition with the authority having jurisdiction before fabrication, because requirements differ materially between editions.
1.3.3Each gas and vacuum service shall be provided as a separate and complete system with its own source, distribution piping, shutoff valves, alarms, and station terminals.
1.4 Systems Included
NOTE Each gas or vacuum service is an independent system; a single connection between two services (a cross-connection) is catastrophic and is the central hazard the verification protocol exists to detect. (1.4.1)
1.4.2The following systems shall be provided where indicated for the project.
☑ Oxygen (O2)
☑ Medical air
☑ Medical-surgical vacuum
☑ Waste anesthetic gas disposal (WAGD)
☐ Nitrous oxide (N2O)
☐ Nitrogen (N2)
☐ Instrument air
☐ Carbon dioxide (CO2)
NOTE Medical air is a patient-breathed gas meeting the USP medical air monograph and is a different system from instrument air. (1.4.3)
1.4.4Instrument air drives surgical tools and pneumatic controls and shall be provided as a separate source, distribution, and labeled system from medical air.
NOTE Combining medical air and instrument air onto a single system is a code violation; the two systems serve different purposes and have different purity and pressure requirements. (1.4.5)
1.5 Scope Exclusions
NOTE This standard does not cover the following, which are specified elsewhere: (1.5.1)
- Laboratory specialty gases not serving patient care, covered by Laboratory Gas Systems
- Natural gas and fuel gas piping, covered by Fuel Gas Piping
- General-purpose compressed air for shop and pneumatic tools, covered by Compressed Air Systems
- HVAC and building exhaust systems, except where they serve a passive WAGD termination coordinated under this standard
2 System Category
NOTE NFPA 99 classifies medical gas systems by the risk that a failure poses to patients, not by facility type. The Category determines source redundancy, alarm requirements, permissible equipment, and the essential-power connection. The three categories are: (2.1)
- Category 1 applies where system failure is likely to cause major injury or death of patients or caregivers.
- Category 2 applies where system failure is likely to cause minor injury to patients or caregivers.
- Category 3 applies where system failure is unlikely to cause injury but could cause patient discomfort.
NOTE Most acute-care hospital systems serving operating rooms, intensive care, post-anesthesia care, procedure rooms, and inpatient nursing are Category 1. Defaulting to Category 2 or 3 for spaces that are actually Category 1, such as pre-op and PACU, produces non-compliant installations and AHJ rejection; the Category must be confirmed, not assumed. (2.1.1)
2.1.2The system Category shall be established by the engineer of record in consultation with the authority having jurisdiction before design proceeds.
2.1.3The Category established for the project shall be recorded on the contract documents.
● Category 1
○ Category 2
○ Category 3
2.1.4Source equipment redundancy shall be provided as required for the established Category, with duplex minimum for all Category 1 source equipment.
3 Referenced Standards
NOTE The following standards are referenced in this document. The edition adopted by the authority having jurisdiction governs where an edition is not stated. (3.1)
| Standard |
Title |
| NFPA 99 |
Health Care Facilities Code |
| NFPA 50 |
Standard for Bulk Oxygen Systems at Consumer Sites |
| NFPA 70 |
National Electrical Code (Article 517) |
| NFPA 110 |
Standard for Emergency and Standby Power Systems |
| ASTM B819 |
Standard Specification for Seamless Copper Tube for Medical Gas Systems |
| CGA G-4.1 |
Cleaning Equipment for Oxygen Service |
| CGA G-4 |
Oxygen |
| CGA V-5 |
Diameter Index Safety System (DISS) |
| ANSI/AWS A5.8 |
Specification for Filler Metals for Brazing and Braze Welding |
| ASSE/IAPMO/ANSI 6010 |
Professional Qualifications Standard for Medical Gas Systems Installers |
| ASSE/IAPMO/ANSI 6020 |
Professional Qualifications Standard for Medical Gas Systems Inspectors |
| ASSE/IAPMO/ANSI 6030 |
Professional Qualifications Standard for Medical Gas Systems Verifiers |
| ASSE/IAPMO/ANSI 6040 |
Professional Qualifications Standard for Medical Gas Systems Maintenance Personnel |
| ASSE/IAPMO/ANSI 6060 |
Professional Qualifications Standard for Medical Gas Systems Designers |
4 Submittals
NOTE Submittals establish the chain of accountability that NFPA 99 depends on: who designed the system, who is qualified to install it, what product was furnished, and who independently verified it before patient use. (4.1)
4.2 Action Submittals
NOTE The Contractor shall submit the following action submittals for review before fabrication or ordering of material. (4.2.1)
- Shop drawings showing pipe routing, sizes, valve and outlet locations, zone boundaries, and alarm point assignments
- Product data for source equipment, manifolds, compressors, vacuum pumps, valves, alarm panels, and station outlets
- Pipe and fitting product data confirming ASTM B819 marking and cleaning for oxygen service
- Brazing procedure specification including filler metal and nitrogen purge method
- Flow calculations demonstrating pipe sizing per the NFPA 99 sizing method at peak demand
- Connector type and indexing for each gas, confirming facility-wide uniformity
☑ Shop drawings (routing, sizes, valves, outlets, zones, alarm points)
☑ Product data (source equipment and components)
☑ Pipe and fitting data (ASTM B819 marking, oxygen-cleaned)
☑ Brazing procedure specification with nitrogen purge
☑ Flow calculations (NFPA 99 method)
☑ Connector type and indexing schedule
NOTE The Contractor shall submit the following informational submittals documenting personnel qualifications. (4.3.1)
- ASSE 6010 certification for each installer who brazes or assembles medical gas piping
- ASSE 6060 designer qualification for the system designer where required by the adopted edition
- Evidence that the verifier is ASSE 6030 certified and independent of the installing contractor
☑ ASSE 6010 installer certifications
☐ ASSE 6060 designer qualification
☑ ASSE 6030 verifier certification and independence statement
4.4 Closeout Submittals
NOTE The Contractor shall submit the following closeout submittals before the system is placed in service for patient care. (4.4.1)
- Record drawings showing as-installed routing, valve and outlet locations, and zone boundaries
- Complete verification report from the independent ASSE 6030 verifier
- Test reports for pressure, cross-connection, purity, flow, and alarm testing
- Operation and maintenance manuals for all source equipment
- Valve and zone identification schedule keyed to the record drawings
☑ Record drawings
☑ Independent verifier report (ASSE 6030)
☑ Test reports (pressure, cross-connection, purity, flow, alarm)
☑ Operation and maintenance manuals
☑ Valve and zone identification schedule
5 Quality Assurance
NOTE NFPA 99 makes personnel qualification a hard requirement, not a recommendation: only certified installers may join piping, and only an independent certified verifier may release the system for use. Calling out merely experienced contractors creates liability and invites AHJ rejection. (5.1)
5.2 Installer Qualifications
5.2.1Personnel who braze or assemble medical gas piping shall be certified to ASSE 6010.
5.2.2The installing contractor shall maintain current ASSE 6010 certification records for all such personnel on site.
NOTE ASSE 6010 requires minimum mechanical or plumbing experience, a formal training course, a written examination, and a practical brazing examination; the certification is the evidence that the installer can produce sound oxygen-clean joints. (5.2.3)
5.3 Inspector and Designer Qualifications
5.3.1Inspections performed on behalf of the authority having jurisdiction or the owner shall be performed by personnel certified to ASSE 6020.
5.3.2Where the adopted edition requires designer qualification, the system designer shall be certified to ASSE 6060.
5.4 Verifier Independence
5.4.1Final verification shall be performed by a verifier certified to ASSE 6030.
5.4.2The verifier shall be independent of the installing contractor.
NOTE Verifier independence exists so that the party releasing the system for patient use has no financial interest in passing a defective installation; an installer cannot verify its own work. (5.4.3)
5.5 Maintenance Personnel Qualifications
5.5.1Personnel performing ongoing maintenance on the installed system shall be certified to ASSE 6040.
6 Source Equipment
NOTE The source supplies the entire facility; NFPA 99 requires every Category 1 source to be redundant so that maintenance or failure of one component never interrupts supply. Source selection is driven by gas, demand, and the Category. (6.1)
6.2 Oxygen Source
6.2.1The oxygen source shall be one of the following configurations as indicated for the project demand.
● Bulk liquid oxygen with reserve cylinder manifold
○ Automatic alternating high-pressure cylinder manifold
○ Liquid oxygen with secondary liquid reserve
6.2.2A bulk liquid oxygen source shall comply with NFPA 50 for storage, vaporizers, and manifolds.
6.2.3A bulk liquid oxygen system shall include a reserve supply sized to maintain service during primary tank changeover or interruption.
6.2.4The bulk oxygen storage location shall be coordinated with the authority having jurisdiction for separation distances and access. bulk oxygen storage location NOTE Bulk liquid oxygen is the standard source for hospitals because liquid storage holds far more oxygen per unit volume than cylinders and reduces the frequency of deliveries; the reserve exists to bridge a primary failure. (6.2.5)
6.3 Cylinder Manifold Source
6.3.1A high-pressure cylinder manifold serving a continuous-use gas shall be the automatic alternating type with primary and reserve banks.
6.3.2An automatic alternating manifold shall switch from the depleted bank to the full bank without interruption of supply and without manual intervention.
NOTE Automatic changeover prevents an unattended depletion from interrupting a life-critical gas; the operator is alerted to change cylinders but supply continues uninterrupted. (6.3.3)
● Automatic alternating, two-bank (primary + reserve)
○ Automatic alternating with reserve header
○ Manual changeover (Category 3 only)
6.4 Medical Air Source
6.4.1The medical air compressor system shall be configured for the established Category, with duplex minimum for Category 1.
● Duplex
○ Triplex
○ Quadruplex
6.4.2A multiplex compressor system shall sequence as lead, lag, and standby so that any single compressor can be removed from service while the system continues to meet peak demand.
6.4.3Medical air shall meet the USP medical air monograph for dew point, carbon monoxide, carbon dioxide, particulate, and oil content.
6.4.4The medical air system shall include dryers and filtration to achieve the required purity.
6.4.5The medical air system shall include continuous dew point monitoring.
NOTE Continuous dew point monitoring is mandatory for Category 1 medical air because moisture in breathing air supports microbial growth and corrodes downstream equipment; omitting the monitor is a code compliance gap. (6.4.6)
6.4.7Medical air shall be drawn from a source free of contamination and shall not be taken from the same intake as a vacuum or WAGD exhaust.
6.5 Instrument Air Source
6.5.1Where instrument air is provided, it shall be supplied by a dedicated oil-free compressor system separate from the medical air system.
6.5.2The instrument air system shall include drying and filtration to achieve the required purity class.
● Class 1.2.1
○ Class 1.3.1
○ Class 2.2.1
6.6 Medical-Surgical Vacuum Source
6.6.1The medical-surgical vacuum pump system shall be configured for the established Category, with duplex minimum for Category 1.
● Duplex
○ Triplex
○ Quadruplex
● Dry-running claw
○ Dry-running scroll
○ Oil-sealed liquid ring
○ Oil-lubricated rotary vane
6.6.2The vacuum pump system shall sequence as lead, lag, and standby so that any single pump can be removed from service while the system continues to meet peak demand.
6.6.3The vacuum source shall include a receiver and a bacteria-retentive separation arrangement at the source.
6.7 WAGD Source
NOTE Waste anesthetic gas disposal removes exhaled and excess anesthetic agent from anesthetizing locations to protect staff from chronic exposure; it is kept separate from medical-surgical vacuum to avoid loading the vacuum pumps with anesthetic agent. (6.7.1)
6.7.2The WAGD system shall be one of the following types as indicated for the project.
● Active (dedicated vacuum producer)
○ Passive (venturi or dedicated exhaust fan)
6.7.3An active WAGD system shall use a dedicated vacuum producer with its own receiver, separate from the medical-surgical vacuum system.
6.7.4WAGD exhaust shall terminate outside the building in a location that prevents re-entry of the discharged gas.
NOTE WAGD exhaust termination conflicts with outside air intakes are a common late-stage problem requiring costly rerouting; the termination shall be coordinated with the HVAC and architectural disciplines early in design. (6.7.6)
6.8 Source Electrical
6.8.1Category 1 source equipment shall be connected to the essential electrical system per NFPA 99 and NFPA 110.
NOTE Connecting Category 1 compressors, vacuum pumps, or critical alarms to normal power only is a recurring coordination failure; the connection to the essential electrical system shall be confirmed on the panel schedules. (6.8.2)
● Equipment branch
○ Critical branch
○ Life safety branch
6.8.3Source equipment power, grounding, and bonding shall comply with NFPA 70 Article 517.
6.9 Auxiliary Connection
NOTE The 2024 edition of NFPA 99 requires an auxiliary connection on the patient side of the source valve so a temporary or supplemental source can be connected during maintenance or source failure; omitting it fails AHJ review under that edition. (6.9.1)
6.9.2Where the adopted edition requires it, each system shall include an auxiliary connection on the patient side of the source shutoff valve.
7 Distribution Piping
NOTE Distribution piping carries the gas from the source to every outlet. The tube must be specifically cleaned for oxygen service, because hydrocarbon residue in an oxygen line is a fire hazard, and the joints must be made without internal oxide scale. (7.1)
7.2 Tube Material
7.2.1Distribution tube shall be seamless copper conforming to ASTM B819.
7.2.2Tube shall be furnished cleaned for oxygen service and capped at the factory.
NOTE Substituting standard ACR copper tube for ASTM B819 tube is a code violation: ACR tube is not cleaned for oxygen service. Only ASTM B819 tube marked OXY, MED, OXY/MED, OXY/ACR, or ACR/MED meets NFPA 99. (7.2.3)
7.2.4Tube wall thickness shall be Type K or Type L as indicated for the application.
NOTE Type L tube is identified by a blue marking and Type K by a green marking; both are acceptable where cleaned for oxygen service, with Type K typically reserved for underground or high-pressure runs. (7.2.5)
7.2.6Factory caps shall remain in place until the moment of assembly to preserve the cleaned interior.
7.3 Fittings and Cleanliness
7.3.1Fittings shall be wrought copper or cast bronze cleaned for oxygen service per CGA G-4.1.
7.3.2Components installed in the piping shall be cleaned for oxygen service and shall remain sealed until installation.
7.3.3Any tube, fitting, or component whose factory seal is broken before installation and which cannot be confirmed clean shall be re-cleaned for oxygen service or rejected.
7.4 Pipe Sizing
7.4.1Distribution piping shall be sized by the engineer of record using the NFPA 99 flow calculation method at peak demand.
NOTE Rule-of-thumb sizing leads to pressure-drop failures at peak demand, especially on vacuum systems where undersized mains starve distant inlets; the engineer shall submit flow calculations rather than rely on nominal sizing. (7.4.2)
7.5 Brazing
7.5.1Joints in medical gas piping shall be brazed except where mechanical or threaded connections are specifically permitted.
7.5.2Brazing filler metal shall conform to ANSI/AWS A5.8 and shall be a cadmium-free silver brazing alloy.
○ BCuP series (copper-phosphorus, copper-to-copper)
● BAg series (silver, copper-to-brass and dissimilar)
7.5.3A continuous nitrogen purge shall be maintained through the tube during all brazing of medical gas piping.
7.5.4The nitrogen purge shall be oil-free dry nitrogen and shall flow at a low rate sufficient to displace air without creating positive pressure at the joint.
NOTE Omitting the nitrogen purge causes internal copper-oxide scale to form during brazing; that scale flakes loose, contaminates the gas stream, and can condemn the system. The purge is the single most important fabrication control. (7.5.5)
7.5.6Only personnel certified to ASSE 6010 shall braze medical gas piping.
7.6 Labeling
7.6.1Piping shall be identified with the gas name, color code, and direction of flow at intervals and at each branch, in accordance with NFPA 99.
NOTE Consistent labeling prevents a maintenance worker from cutting into the wrong line and prevents an accidental cross-connection during future renovation. (7.6.2)
7.6.3Valves, zones, and station outlets shall be labeled in accordance with Equipment Labeling. 8 Valves
NOTE Valves isolate the system for maintenance and let staff shut off a gas to a room in an emergency, such as a fire or an outlet leak. Their placement and accessibility are life-safety functions. (8.1)
8.2 Valve Type
8.2.1Shutoff valves in medical gas piping shall be quarter-turn ball valves cleaned for oxygen service.
8.2.2Each valve shall provide clear visual indication of open or closed position.
8.2.3Source, riser, and main line valves shall be lockable or otherwise secured against unauthorized operation.
● Ball valve with position indicator, lockable
○ Ball valve with position indicator
8.3 Zone Valve Boxes
NOTE Zone valve boxes provide a single accessible location where staff can shut off each gas serving a defined area; they shall be located where they are visible and reachable in an emergency. (8.3.1)
8.3.3Each zone valve box shall contain a labeled shutoff valve for every gas serving the zone.
8.3.4Each zone valve box shall be located outside the zone it controls so the valve remains accessible when the zone itself is the emergency.
8.3.5The zone valve box and area alarm panel may be combined in a single enclosure or provided as separate components.
● Combination zone valve box and area alarm panel
○ Separate zone valve box and area alarm panel
9 Alarms
NOTE The alarm system is how staff learn that a source is failing or a pressure is abnormal before it reaches the patient. NFPA 99 requires a tiered arrangement: local alarms at the source, area alarms at each zone, and master alarms at two staffed locations. (9.1)
9.2 Master Alarms
9.2.1Master alarm signals shall be annunciated at not fewer than two locations, each continuously staffed or monitored.
NOTE Master alarm locations shall be selected so that a single event cannot disable all annunciation, such as the main monitoring station and the facility engineering office. (9.2.2)
9.2.3The master alarm panel shall monitor source equipment status, reserve status, and main line pressures for each system.
9.2.4The master alarm panel shall provide both visual and audible annunciation.
9.2.5The master alarm panel shall be provided with not less than 20% spare monitored point capacity for future expansion.
NOTE Master alarm panels are routinely sized for current zones only, forcing panel replacement when the facility adds zones; the spare-capacity requirement prevents that. (9.2.6)
9.3 Area Alarms
9.3.1An area alarm panel shall be provided for each zone to monitor the pressure of every gas serving that zone.
9.3.2Area alarm panels shall provide both visual and audible annunciation and a means to silence the audible signal while retaining the visual indication.
9.4 Local and BAS Integration
9.4.1Local alarms shall be provided at source equipment to indicate operating and fault conditions at the equipment itself.
9.4.2Alarm panels shall provide dry-contact or equivalent outputs for integration with the building automation system where indicated.
● Dry-contact outputs to BAS
○ Network protocol gateway to BAS
○ No BAS integration
10 Station Outlets and Inlets
NOTE Station outlets and inlets are the terminals where staff connect equipment at the bedside or in the operating room. Connector indexing is gas-specific and non-interchangeable so that an oxygen device cannot be plugged into a nitrous line. (10.1)
10.2 Connector Type
10.2.1All station outlets and inlets shall use a single connector type and indexing system facility-wide.
NOTE Mixing connector types between drawing sheets, or failing to match the existing facility standard, produces non-interchangeable outlets that force medical-equipment adapter changes; the connector type shall be confirmed against the facility standard before specifying. (10.2.2)
● Latch-key quick-connect
○ Pin-indexed quick-connect
○ Geometric non-interchangeable quick-connect
○ NIST quick-connect
10.2.3High-pressure threaded outlets shall use DISS connections conforming to CGA V-5.
10.2.4Each outlet and inlet shall be gas-specific and non-interchangeable with any other gas served in the facility.
10.3 Outlet Construction
10.3.1Each station outlet and inlet shall include a primary and secondary check arrangement permitting service of the connector without shutting down the zone.
10.3.2Outlet bodies and components in contact with the gas shall be cleaned for oxygen service.
● Flush wall mount
○ Surface wall mount
○ Ceiling column
○ Ceiling-mounted articulating arm
11 Testing
NOTE Testing is divided into installer tests performed during construction and the final verification performed by the independent ASSE 6030 verifier. The verification is what releases the system for patient use, and its scope must be defined to avoid disputes at closeout. (11.1)
11.2 Installer Tests
11.2.1The installer shall perform an initial pressure test on each piping system after installation and before concealment.
11.2.2The installer shall perform a standing pressure test to confirm the system holds pressure over time without loss.
11.2.3The installer shall perform a purge and particulate test to confirm the interior of the piping is clean before connecting outlets.
11.3 Verification Scope
NOTE Specifying only verify per NFPA 99 without defining scope leads to closeout disputes over which outlets, which gases, and who witnesses; the verification scope shall be defined completely. (11.3.1)
NOTE The independent verifier shall perform the following verification tests on the completed system. (11.3.2)
- Standing pressure test of each system
- Cross-connection test confirming each outlet delivers only its intended gas
- Valve test confirming each valve controls the intended zone and gas
- Alarm test confirming every monitored point annunciates correctly
- Purity test confirming each gas and air system meets its required purity
- Flow and pressure-drop test at representative outlets under simulated demand
- Source equipment test confirming changeover, redundancy, and reserve operation
☑ Standing pressure test
☑ Cross-connection test (all outlets)
☑ Valve and zone test
☑ Alarm test (all points)
☑ Purity test (all gas and air systems)
☑ Flow and pressure-drop test
☑ Source equipment changeover and reserve test
11.4 Cross-Connection Test
NOTE The cross-connection test confirms that every outlet of every gas delivers only the gas it is labeled for. A single cross-connection can deliver nitrous oxide or vacuum where oxygen is expected, with fatal consequences. (11.4.1)
11.4.2Every station outlet in the facility shall be individually tested for cross-connection.
11.4.3The cross-connection test shall be performed with all systems pressurized one at a time so that any wrong connection is detected.
11.4.4The cross-connection test shall be witnessed and documented for project closeout.
12 Installation
NOTE Installation requirements ensure the system is supported, braced, and protected so that the verified-clean piping reaches the patient intact. (12.1)
12.1.1Piping shall be installed by personnel certified to ASSE 6010.
12.1.2Piping shall be supported at intervals appropriate to the tube size and shall be protected from physical damage where exposed.
12.1.3Dielectric separation shall be provided where copper medical gas tube contacts dissimilar metal supports.
12.1.5Penetrations through fire-rated assemblies shall be firestopped to maintain the rating of the assembly.
12.2 Seismic Bracing
12.2.1Source equipment, manifold racks, compressors, vacuum pumps, and distribution piping shall be seismically braced in accordance with the building code and ASCE 7 for the facility seismic design category.
NOTE Seismic bracing of medical gas equipment is frequently left uncoordinated between the mechanical and structural disciplines; equipment anchorage shall be reviewed by the structural engineer of record. (12.2.2)
13 Delivery, Storage, and Handling
NOTE The value of factory-cleaned tube is lost if the interior is contaminated during storage; handling controls preserve oxygen cleanliness from delivery through installation. (13.1)
13.1.1Tube, fittings, and components shall be delivered with factory caps and seals intact.
13.1.2Tube and components shall be stored under cover, off the ground, and protected from moisture, dust, and oil.
13.1.3Caps and seals shall be removed only at the moment of assembly.
13.1.4Any item with a damaged or missing cap shall be re-cleaned for oxygen service or rejected.
14 Warranty
NOTE The warranty assigns responsibility for latent defects in source equipment and installation after the system is in service. (14.1)
14.1.1The Contractor shall warrant the installed system against defects in materials and workmanship for the warranty period.
14.1.2Source equipment shall carry the manufacturer's standard warranty, which shall be transferred to the owner.
● 1 year
○ 2 years
○ 3 years
15 Spare Parts
NOTE Stocking spares for source equipment and outlets lets the facility restore service quickly without interrupting patient care while replacement parts are procured. (15.1)
NOTE The Contractor shall furnish the following spare parts to the owner at closeout. (15.1.1)
- Spare station outlet and inlet assemblies for each gas and connector type
- Spare zone valve box components
- Spare alarm panel sensors and indicators
- Source equipment consumables, including filters and dryer media
☑ Station outlet/inlet assemblies (each gas and connector type)
☐ Zone valve box components
☐ Alarm panel sensors and indicators
☑ Source equipment filters and dryer media