5.5 Labeling, Identification & Color Codes
Key Takeaways
Pipe labels must show the gas name or chemical symbol and its color code, and they must appear at least every 20 ft, at least once in or above every room, on both sides of walls penetrated, and at least once per story on risers.
Medical gas piping may not be painted.
Standard colors include oxygen green/white (or white/green), medical air yellow/black, nitrous oxide blue/white, nitrogen black/white, vacuum white/black, WAGD violet/white, and instrument air red/white.
Shutoff valve labels show the gas name or symbol, color code, rooms or areas served, and a caution not to close or open the valve except in an emergency.
Zone valve box labels must be visible through the cover or replicated outside, but never attached to the removable cover.
The Master Table: Names, Colors and Pressures
NFPA 99 Table 5.1.11 sets the designation colors and standard pressures. Pipe labels, valve labels, and outlets all use it.
| Gas service | Abbreviation | Colors (background/text) | Standard pressure |
|---|---|---|---|
| Medical air | Med air | Yellow/black | 50-55 psi |
| Carbon dioxide | CO2 | Gray/black or gray/white | 50-55 psi |
| Helium | He | Brown/white | 50-55 psi |
| Nitrogen | N2 | Black/white | 160-185 psi (standard for support gas) |
| Nitrous oxide | N2O | Blue/white | 50-55 psi |
| Oxygen | O2 | Green/white or white/green | 50-55 psi |
| Oxygen/carbon dioxide mixture | O2/CO2 n% | Green/white | 50-55 psi |
| Medical-surgical vacuum | Med vac | White/black | 15-30 in. HgV |
| Waste anesthetic gas disposal | WAGD | Violet/white | Varies with system type |
| Medical-surgical vacuum/WAGD combination | Med-surg/WAGD | White/black and violet/white | 15-30 in. HgV |
| Instrument air | — | Red/white | 160-185 psi (standard for support gas) |
| Other mixtures | Gas A%/Gas B% | Major gas for background, minor gas for text | None |
| Nonmedical air and dental air | — | Yellow and white diagonal stripe/black | None |
| Nonmedical vacuum and dental vacuum | — | White and black diagonal stripe/black boxed | None |
| Laboratory air | — | Yellow and white checkerboard/black | None |
| Laboratory vacuum | — | White and black checkerboard/black boxed | None |
The valve and outlet labeling rules treat 50-55 psi as standard for patient gases and 160-185 psi as standard for nitrogen and instrument air. Anything outside those ranges is a nonstandard pressure and must be stated on the label.
Note
CGA C-9 sets cylinder color marking, and its colors are not always the same as the pipeline label colors. On a pipeline, the label text, meaning the gas name or symbol, is what identifies the service. Never identify a pipe or a cylinder by color alone.
Pipe Labeling
Content. Piping is labeled with stenciling or adhesive markers that show:
- The name of the gas or vacuum system, or its chemical symbol, per Table 5.1.11
- The system's color code
Where positive-pressure piping operates at a nonstandard pressure, the label also shows the operating pressure. Where a vacuum system also serves WAGD, the piping in the immediate area of the WAGD system is labeled to show both systems.
Location. Pipe labels must be placed:
| Rule | Example |
|---|---|
| At intervals of not more than 20 ft (6.1 m) | A 90 ft corridor run needs labels at no more than 20 ft spacing, so at least five labels plus any others the rules below require |
| At least once in or above every room | A short pass-through above a storage room still gets a label |
| On both sides of walls or partitions the piping penetrates | One label on each side of a fire-rated wall |
| At least once in every story height a riser passes through | A riser crossing eight floors gets at least eight labels |
Never paint medical gas piping. Paint hides tube markings, labels, and leaks.
Intakes, exhausts and relief vents. Piping for compressor intakes, vacuum exhausts, and relief valve vent lines is labeled with the same content and its specific function, so nobody mistakes it for patient supply piping. The medical air intake itself is labeled so it is clearly identified as a medical air intake.
Shutoff Valve Identification
Every shutoff valve label must include:
- The name or chemical symbol of the gas or vacuum system
- The system's color code
- The rooms or areas served
- A caution not to close or open the valve except in an emergency
For nonstandard pressures, the valve label also shows the operating pressure. Where a vacuum system serves WAGD, valves on the source side of the WAGD connection are labeled for both systems.
Required wording by valve type (in substance)
| Valve | Label reads in substance |
|---|---|
| Source valve | SOURCE VALVE FOR THE (source or gas name) |
| Main line valve | MAIN LINE VALVE FOR THE (gas or vacuum) SERVING (name of building) |
| Riser valve | RISER FOR THE (gas or vacuum) SERVING (area or building served by that riser) |
| Service valve | SERVICE VALVE FOR THE (gas or vacuum) SERVING (area or building served by that valve) |
| Zone valve box | ZONE VALVES FOR THE (gas or vacuum) SERVING (rooms or spaces served) |
The zone valve box label must be visible from outside through the cover, or replicated on the outside, but it must not be fixed to the removable cover.
Station Outlet and Inlet Identification
Each outlet and inlet is identified with:
- The name or chemical symbol of the gas or vacuum
- The color code
Outlets at nonstandard pressures show the operating pressure in addition to the gas name. In sleep labs, outlets downstream of a flow control device carry a warning not to use them for ventilating patients.
Buried and Concealed Piping
- Buried piping outside buildings gets a continuous tape or marker immediately above the pipe that names the pipeline.
- During system inspection before concealment, the inspector confirms that labeling and valve tagging are present and correct for all concealed components and piping (Section 7.2). Labels that go missing behind a finished ceiling are hard to fix later.
- The verifier checks labeling again and confirms through the cross-connection and valve tests that each outlet and valve label matches the piping.
What color combination does NFPA 99 assign to waste anesthetic gas disposal (WAGD) piping labels?
White/black
Violet/white
Red/white
Brown/white
A 100 ft run of medical air piping passes above a corridor with no walls or rooms along the way. What is the maximum spacing NFPA 99 allows between pipe labels?
10 ft
25 ft
50 ft
20 ft
Where may the label for a zone valve box assembly be placed?
Visible through or copied outside the cover, never on the removable cover
Only on the removable cover itself, so it is visible from the corridor
Only inside the box, attached to each valve handle where staff will see it
On the ceiling grid above the box
Sections you finish are checked off in the contents.