print logo

OSHA Pipe Labeling Requirements

By Graphic Products Editorial Staff

osha pipe marking

Pipe marking is an easily-overlooked but vital part of maintaining a safe workplace. Properly marked pipes (whether carrying hazardous or benign contents) inform employees, contractors, vendors, visitors, and emergency responders about any potential hazards associated with pipe contents. These simple but effective markings help ensure workplace safety and improve productivity.

Does OSHA have pipe labeling or pipe marking requirements?

OSHA does not outline requirements specific to pipe labeling for most industries. Instead, OSHA references the ANSI/ASME A13.1 pipe marking standard for the pulp and paper industry, textiles, and for welding and cutting. In effect, this makes ANSI/ASME A13.1 OSHA’s preferred pipe labeling system.

Pipe labeling also falls within the scope of OSHA’s General Duty Clause, which requires employers to provide a safe workplace. Where pipe marking would inform workers about a potential hazard, failing to mark the pipes may violate this requirement. Companies whose pipes aren’t labeled in compliance with ANSI/ASME A13.1 may be subject to an OSHA citation.

ANSI and ASME’s recommendations have become the single broadest recommendation for pipe marking in the United States. OSHA’s pipe marking requirements apply to pipes within a workplace. A different government agency, PHMSA (the Pipeline and Hazardous Materials Safety Administration), sets the requirements for marking the routes of underground pipelines. Pipe marking within a facility may also follow a variety of other standards for specific applications. For example, there is an IIAR standard for ammonia refrigeration piping, and a CGA standard for medical gas.

How can I comply with OSHA labeling requirements?

ANSI/ASME A13.1 states that labels should be placed on pipes:

  • Adjacent to all valves and flanges
  • Adjacent to all changes in pipe direction
  • On both sides of wall, floor or ceiling penetrations
  • Every 50 feet on straight runs of pipe (or every 25 feet in congested areas)

ANSI/ASME A13.1 recommends a color code based on the type of hazard posed by a pipe’s contents. The recommended color code is:



Fire quenching fluids

White text on red

Toxic and corrosive fluids

Black text on orange

Flammable fluids

Black text on yellow

Combustible fluids

  White text on brown


  White text on green

Compressed air

White text on blue 

This color code immediately shows the hazards associated with a pipe and enhances safety by identifying fire quenching systems (using red).

Requirements also dictate minimum label and text sizes, each based on the pipe’s outer diameter. Minimum sizes are outlined below:

Pipe outer diameter

Min. Label Length

Min. Letter Height

0.75 - 1.25 inches

8 inches

0.5 inch

1.5 - 2.0 inches

8 inches

0.75 inch

2.5 - 6.0 inches

12 inches

1.25 inch

6 - 100 inches

24 inches

2.5 inch

greater than 10 inches

32 inches

3.5 inch

Which pipes must be labeled?

For most industries, ANSI/ASME A13.1 is a recommendation, not a mandate. But OSHA's General Duty Clause covers all potential hazards in a workplace, so you could be fined if you don't label pipes where the following apply:

  1. Pipe contents are hazardous, or could generate hazardous conditions.
  2. The pipe serves a safety purpose, as part of hazard prevention or emergency response.
  3. Flow must be redirected, shut off, or adjusted to allow for maintenance or other expected work.
  4. The pipe or its contents could affect the procedures followed during an emergency.

Confusion over these pipe contents could result in injury or even death. As a result, these pipes must be labeled. However, ANSI/ASME A13.1 recommends marking all pipes with their contents. This helps with general facility maintenance and communication.

In addition to this recommendation, some industries and jurisdictions have additional legal requirements as well. The first step in assessing your facility is to understand what regulations apply there. Check with your local authorities. Pipe systems should be inspected at least once a year to ensure all markers are in place and in good condition.

What are some pipe marking best practices?

We offer a free Best Practice Guide to Pipe Marking that outlines recommended efforts for implementing, maintaining, and updating a pipe marking system. The guide provides valuable information for anyone involved with visual communication, compliance, and safety.

We also offer a free Pipe Marking Guide Wall Chart that details which field colors to use, font and label sizes, and where to place labels.

Related Resources