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Everything You Ever Wanted to Know About Pipe Marking

03 February, 2023

A pipe marking best practices resource describing pipe marking requirements, how to retrieve data, and specific sizes and color codes to achieve compliance.


I'm going to skip the part where I share stories of safety managers who didn't ensure pipes were properly labeled, resulting in employee injury or death. You've heard the horror stories and you know to take this seriously, so let's get right to what you need to know.

Collecting Pipe Data

First, you need to do a safety audit to determine which pipes need to be labeled or relabeled. Walk through your facility and photograph pipes that need to be labeled and add notes. Another approach, if you have access to a piping system plan that maps your facility's network of pipes, is to take a copy of the plan and number the locations that require labels, cross-referencing those numbers with the following information for each case:

  • Pipe diameter
  • Pipe contents
  • Direction of flow
  • Special situations (pipes that are greasy or hot will require a ladder to access, etc.)
  • Optional: it may be helpful to include other details such as pressure or temperature of contents.

Exceptions To the Rules

It's important to know that some industries and localities are held to different standards. The pulp and paper industry, for instance, is required to apply ANSI/ASME A13.1 in its mills, according to 29 CFR 1910.261(3)(ii).

Hospitals and healthcare facilities often follow the National Fire Protection Association (NFPA) standard NFPA 99: Healthcare Facilities Code, which covers many aspects of a hospital or healthcare facility and includes labeling for pipes.

Seafaring ships and vessels have their own standard, allowing language-independent identification of pipes. The international standard ISO 14726:2008 (or ISO 14726) uses bands of color to identify pipes on seafaring ships and vessels.

Also, ammonia refrigeration has its own set of standards. The most common standard for ammonia refrigeration piping is from the International Institute of Ammonia Refrigeration (IIAR), published in their IIAR Bulletin No. 114 and sometimes referred to as the IIAR label standard.

Some jurisdictions may also be covered by other legal requirements. Check with your local authorities to ensure that you are complying with municipal and state law.

Label Color Codes

In 2007, ASME introduced a change to the pipe marking color coding system. Previously the colors were determined based on the severity of the hazard, but they're now based on the type of hazard present. The color codes are the font color followed by label color, for example, black on yellow is black type on a yellow label.

Hazard Type Description Color Code
Flammable Vapors that can burn in the air, or fluids that can release a vapor that can burn in the air Black on yellow
Combustible Any contents that could pose a fire hazard, but do not qualify as Flammable White on brown
Toxic and Corrosive Contents are hazardous to health when released Black on orange
Fire-Quenching Contents are part of a fire-fighting system, such as water sprinklers or halon systems. The contents themselves may or may not be hazardous. White on red
Other Water Any water pipes that are not part of a fire-fighting system. White on green
Compressed Air Any vapors under pressure that do not fit a different category. White on blue
User-Defined Defined by the facility White on black
User-Defined Defined by the facility Black on white
User-Defined Defined by the facility White on purple
User-Defined Defined by the facility White on gray


Your facility can use the four "wild card" color combinations however desired, as long as the system is consistent across your facility, and you document it and train your workers to recognize it.

Label Size and Font Size

Next, is picking the label size. There are standards to this part too, as well as the minimum height of letters.

Outside Diameter
(including covering)
Recommended Minimum Label Size Minimum Height of Letters
.75" ? 1.25" 1" x 8" .5"
1.5" ? 2" 1" x 8" .75"
2.5" ? 6" 2" x 12" 1.25"
8" ? 10" 3" x 24" 2.5"
Over 10" 4" x 32" 3.5"


If the pipe diameter is less than 0.75", you should use a hanging tag.

The label itself will need to identify the pipe contents and the direction of flow. Abbreviations may be used but it must be clear what they mean. Optionally it can include details such as pressure or temperature.

Placement of Markers

The standard also emphasizes label placement to assure that labels are placed often enough in your facility, particularly in pipe-dense areas, and that they're visible without having to travel a long distance. In an emergency you don't want employees running the length of the pipe, looking for evidence of its contents, instead of coping with the hazard presented by the leaking contents.

Labels should face the angle of a typical approach. If the pipe is in a high ceiling and people would typically walk beneath it, the label should be placed on the underside of the pipe. A typical recommendation for label spacing is no more than 50 feet apart on straight runs or 25 feet in congested areas. Place labels adjacent to pipe directional changes. Put them on both sides of wall or floor penetrations so they're visible on both sides and adjacent to all valves and flanges.

Pipe Marking Resources

To achieve pipe marking compliance in your facility, Duralabel carries a variety of pipe marking resources to make this venture easier. Discover pipe marking labels that are right for your workplace and the specific challenges present in your environment including valve tags, tag stock, and other pipe marking supplies.