A medical gas system is the piping, valves, alarms and outlets that deliver oxygen, medical air, nitrous oxide, nitrogen and vacuum to patient care areas, and in the U.S. it is built to NFPA 99, the Health Care Facilities Code. It's installed by certified installers, tested as it's built, and tested again as a finished system before it's put into use.
This guide is for hospital facilities staff, clinic owners and anyone planning a buildout or renovation that includes piped gases. It covers what's in a system, which rules apply, and what happens between the last brazed joint and the first patient.
What a medical gas system includes
NFPA 99 sets out standard names and identifications for the gases and vacuum systems it covers. That list includes:
| System | Typical use |
|---|---|
| Oxygen | Patient breathing, anesthesia, respiratory therapy |
| Medical air | Patient breathing and respiratory equipment |
| Nitrous oxide | Anesthesia and sedation, including in dental offices |
| Nitrogen | Driving surgical tools and equipment, not for breathing |
| Carbon dioxide | Some surgical procedures |
| Medical-surgical vacuum | Suction at the bedside and in procedure rooms |
| Waste anesthetic gas disposal (WAGD) | Removing exhaled anesthetic gas from the room |
That list comes from the code text reproduced in NFPA's committee documents for NFPA 99, which also covers helium and oxygen/carbon dioxide mixtures. Not every facility has every gas. A dental office may only pipe oxygen, nitrous oxide, air and vacuum, while a hospital operating suite may have all of them.
Beyond the pipe itself, every system has:
- A source: cylinder manifolds, a bulk liquid oxygen tank, medical air compressors or vacuum pumps.
- Valves: a source valve, main and riser valves, and zone valves, so staff can shut off one area in an emergency.
- Alarms: panels that warn staff when pressure or vacuum drifts outside its normal range.
- Outlets and inlets: the wall or ceiling connections where equipment plugs in.
The governing standard: NFPA 99
NFPA 99 is the Health Care Facilities Code. Among other things, it covers medical gas systems, cryogenic fluids and dental systems.
NFPA 99 sorts piped gas and vacuum systems by how much risk a failure would pose. Based on the code language in NFPA's committee report:
- Category 1: losing the system is likely to cause major injury or death.
- Category 2: losing it is likely to cause minor injury to patients, staff or visitors.
- Category 3: losing it is not likely to cause injury, but can cause discomfort.
The category drives how much redundancy, alarming and testing the system needs. For dental facilities, the code ties the category to the type of sedation: Category 1 where general anesthesia and deep sedation are performed, Category 2 where only moderate and minimal sedation are performed, and Category 3 where minimal or no sedation is performed. Your designer should establish the category early, because it shapes the whole system.
Which edition applies to your project depends on what your state, local authority and accrediting bodies have adopted. Ask your design team which edition they are designing to.
Who can install it: ASSE 6010
ASSE International publishes a series of professional qualification standards for medical gas work (ASSE Series 6000). The main ones are:
- ASSE 6010: Medical Gas Systems Installers
- ASSE 6020: Medical Gas Systems Inspectors
- ASSE 6030: Medical Gas Systems Verifiers
- ASSE 6040: Medical Gas Systems Maintenance Personnel
NFPA 99 requires installers of medical gas systems to be certified to ASSE 6010. The dental chapter says so regardless of the size of the source, and it adds that a certified installer can't use that certification to oversee people who aren't certified (NFPA 99, 15.4.2.1). In other words, every person brazing the pipe needs the card, not just the foreman. On any bid, ask to see the certifications of the people who will actually be on your job.
How it's installed
Medical gas piping is cleaned copper tube joined by brazing. NFPA 99 requires brazed joints to be continuously purged with oil-free, dry nitrogen while they're made, so copper oxide doesn't form inside the pipe, and the purge has to be checked with an oxygen analyzer before brazing starts (NFPA 99, 5.1.10.4.5). Oxide flakes and residue inside the pipe would otherwise end up in the gas a patient breathes, which is why the work is held to that standard.
Testing and verification before use
A medical gas system goes through two rounds of testing before it's used.
- Installer testing. The installing contractor tests the piping as it's built: blowing it clear, pressure testing it, checking for cross-connections between gases, and holding a standing pressure test. The dental chapter of NFPA 99, for example, lists initial pressure, piping purge, cross-connection and standing pressure tests (NFPA 99, 15.3.3.8.3).
- System verification. After the installer's tests, the completed system is verified. ASSE publishes a separate qualification standard for the people who do this work, ASSE 6030 for verifiers. Ask your design team early what verification will cover, who will perform it, and how much time to leave for it before the space opens.
Full field testing is always required for the final installation, even when parts of the system arrived as factory-tested assemblies, as NFPA's piping committee put it in its response to a proposed change. And the facility itself has a role: in the dental chapter, the responsible facility authority has to review the inspection and testing records before the system is used (NFPA 99, 15.3.3.8.1.4). Keep those records. You'll want them for inspections, accreditation surveys and the next renovation.
Renovations and tie-ins
Most medical gas work in existing buildings is a renovation: a new procedure room, a relocated nurse station, a clinic moving into a former office. The hard part is usually connecting new piping to a system that's in use. That takes planning:
- Know exactly which zones a shutdown will affect, and confirm the zone valve labels match the rooms.
- Schedule the shutdown with clinical staff and have portable supply ready for any patients who need it.
- Expect the new section and the tie-in to be tested and verified before the area is put back in service.
- Update the drawings and the valve and alarm labels to match what was built.
Planning a project
If you're planning a buildout that includes medical gas, settle these early:
- Which gases and how many outlets each room needs
- The risk category, which follows from the procedures and sedation planned
- Where the source equipment goes, and whether existing sources have the capacity
- Who is doing verification, and when it's scheduled relative to occupancy
- The certifications of the installers who will be on site
Medical gas usually goes in alongside other mechanical work, such as new HVAC for the suite or gas piping for other equipment in the building. For medical office owners replacing aging HVAC, commercial geothermal is also worth pricing, since buildings with long operating hours see savings add up fastest.
Next step
We install medical gas piping and systems for hospitals, clinics and other medical facilities across the St. Louis area. Request a free estimate or call 636-327-4238.