Once medical gases and vacuum leave the source equipment, they travel through a tree of brazed copper piping, isolation valves, and monitored alarm points before reaching the patient at a wall outlet, ceiling column, or boom. This Article covers everything between the source and the outlet — the distribution network, the valve hierarchy (main, riser, service, zone, and in-line), the alarm system (master, area, and local), and the layout of station outlets and inlets at the point of care. It does not cover sources, manifolds, or bulk oxygen (its sibling Article), nor redundancy/emergency supply or third-party verification (covered by other Articles in this Chapter).

All of this is governed by NFPA 99, Health Care Facilities Code, primarily Chapter 5 (Gas and Vacuum Systems), interpreted through the lens of the facility's risk category (Category 1 systems serve patients where failure is likely to cause major injury or death — the case for nearly all acute-care medical-gas piping). FGI Guidelines drive how many outlets each clinical space needs; the applicable plumbing/mechanical code (IPC/UPC/IMC) and NEC/NFPA 70 govern supporting trades; and the AHJ, the accreditor (TJC or DNV), and CMS Conditions of Participation enforce it in operation.

The distribution hierarchy: source to outlet

Medical-gas distribution is organized as a descending tree, and the valve and alarm strategy maps onto each level. Understanding the hierarchy is the key to reading a med-gas riser diagram and to knowing what gets shut off when a given valve is closed.

The governing design principle is selective isolation: a single fault, repair, or renovation should be containable to the smallest practical area without dropping gas to the rest of the facility. That is why zone valves are placed so that any patient-care space can be isolated without affecting another smoke compartment, and why the valve is always visible and accessible to the staff responsible for that zone.

Distribution piping and materials

The physical pipeline is as code-regulated as the equipment it connects.

• Tubing material. Positive-pressure medical-gas and medical-vacuum piping is Type L (and, where pressures require, Type K) seamless copper tube, supplied cleaned and capped for oxygen service ("Type L/ACR cleaned for medical gas," delivered with end caps intact). The tube must arrive degreased and stay sealed until installed — hydrocarbons in an oxygen-enriched line are an ignition and contamination hazard.
• Joining method. Joints are brazed with a filler metal (typically a copper-phosphorus or silver-bearing alloy) while purging the interior with oil-free dry nitrogen (NF — nitrogen, oil-free, dry). The nitrogen purge prevents the formation of copper oxide scale on the inside of the joint, which would otherwise flake off and contaminate outlets, clog the tiny orifices of flowmeters, or foul ventilator and anesthesia equipment downstream. The purge is not optional and is a routine inspection focus during verification.
• No flux, no soldering. Soft solder is prohibited on positive-pressure medical-gas lines; flux is generally avoided on the inside of joints. The intent is a clean, oxide-free internal surface.
• Identification. Piping is labeled at intervals and at every wall/partition penetration and valve with the gas name, color code, and direction of flow. Color identification follows the standardized scheme (for example, green for oxygen, yellow for medical air, black for vacuum, and the specified colors for nitrous oxide, carbon dioxide, and nitrogen in U.S. practice). Consistent, frequent labeling is a life-safety feature: it prevents cross-connection during maintenance and renovation.
• Cross-connection prevention. Because every gas uses the same copper tubing, the system relies on rigorous labeling, gas-specific (non-interchangeable) outlet connections, and the cross-connection test during verification to guarantee that oxygen comes out of the oxygen outlet and nothing else. A cross-connected line is one of the most dangerous defects in the building.
• Sizing and pressure. Lines are sized for simultaneous-use (diversity) demand so that pressure at the most remote outlet stays within the standard delivery band under peak flow. Most positive-pressure piped gases operate at a nominal ~50–55 psi delivery pressure (gas-specific bands apply; some support-gas and tool-air services run higher). Vacuum is sized to hold a specified minimum inches-of-mercury at the most remote inlet under full simultaneous load.
• Support, protection, and seismic. Tubing is supported at code intervals, isolated from dissimilar metals, sleeved through fire/smoke barriers with the rated penetration firestopping, and — in OSHPD/HCAI and other high-seismic jurisdictions — braced and anchored to the applicable seismic standard. Med-gas piping that fails in an earthquake defeats the very resilience the system exists to provide.

Valves: the isolation hierarchy

Valves are how the system is partitioned for routine maintenance, emergency shutoff, and phased construction. NFPA 99 defines a layered set of valves, each with a job.

• Source / source-shutoff valves isolate the source equipment from the rest of the system (covered with the source Article).
• Main line valves isolate the main trunk where it enters the building, so the whole facility can be shut off if necessary.
• Riser valves isolate a vertical run, allowing one stack of floors to be worked on while the rest of the building stays in service.