What color code is used for a piping system conveying gaseous elements?

If a facility only has the need for using the ANSI/ASME A13.1 standard, then normal gaseous materials should follow that standard. However, gas mixtures or those that are being used for medical purposes must follow the NFPA 99/CGA C-9 pipe marking standards. It may seem surprising but there are quite a few other pipe marking standards that certain facilities must follow.

Within the NFPA 99/CGA C-9 standard, the three elements that must be included on a pipe marker are:

  • The contents of the pipe
  • The direction of the flow
  • The level of pressure

Many of the gaseous substances in these environments are flammable which is why the NFPA is the entity that has created these standards for OSHA to enforce. The following are the color code combinations that must be used:

  • White lettering on a green background is for oxygen USP
  • White lettering on a gray background is for carbon dioxide
  • White lettering on a blue background is for nitrous oxide
  • Black lettering on an orange background is for cyclopropane
  • White lettering on a brown background is for helium USP
  • White lettering on a black background is for nitrogen NF
  • Black lettering on a yellow background is for medical air USP
  • White lettering on a red background is for instrument air
  • White lettering on a purple background is for waste anesthetic disposal
  • Back lettering on a white and yellow checkerboard pattern is for laboratory air
  • Black lettering on a black and white checkerboard pattern is for laboratory vacuum
  • Black lettering on a white background is for medical-surgical vacuum

There are also regulations regarding gaseous mixtures that must be followed to ensure worker safety. Those standard color combinations can be found here.

Overall, it is good to remember that the ANSI/ASME A 13.1 standard is not the only pipe marking standard out there. There is one pertaining to sea vessels and ones for water treatment facilities, and even extras for commercial buildings.


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