Pipe labeling marking standards are not specifically outlined or defined by OSHA, but standard number 1910.261(a)(3)(i) notes the ASME's (ANSI) standard A13.1 as the recommended scheme for identification of pipe systems.

The ASME Standard for Pipe Identification is a widely used guideline in determining pipe identification requirements. The ASME A13.1-2007 editorial notes indicate that, "A13.1 is intended to establish a common system to assist in identification of hazardous materials conveyed in piping systems and their hazards when released in the environment." It goes on to identify that this scheme provides pipe system identification recommendations for industrial workplaces, power plants, commercial and institutional installations, and buildings used for public assembly.

Editorial Note Source and A13.1-2007 Guide Purchase Information

Pipe Marking Reference Informational Sheet

Brady’s Color and Size Pipe Marking Guide

Download a printer-friendly pipe marking color and size guide for the ANSI standard A13.1.

This e-book will explain the cost savings, improving safety, simplifying preventative maintenance, and much more.

Label Color	Text Color	Color	Pipe Contents
Red	White		Fire-quenching fluids
Orange	Black		Toxic and corrosive fluids
Yellow	Black		Flammable fluids
Brown	White		Combustible fluids
Green	White		Potable, cooling, boiler feed and other water
Blue	White		Compressed air
Purple Gray Black	White		Defined by user
White	Black		Defined by user

Pipe Marker Visibility and Size Requirements

The ANSI standard A13.1 states that, "Markers shall be located so that they are readily visible to plant personnel from the point of normal approach." They need to instantly tell you all you need to know about pipe contents, direction of flow, and whether the contents are hazardous or safe.

Outside Diameter of Pipe or Covering	Length of Color Field	Letter Height
3/4" - 1 1/4" (19-32mm)	5" (127mm)	1/2" (13mm)
1 1/2" - 2" (38-51mm)	8" (203mm)	3/4" (19mm)
2 1/2" - 6" (64-152mm)	12" (304mm)	1 1/4" (32mm)
8" - 10" (203-254mm)	24" (609mm)	2 1/2" (64mm)
10" (254mm) or bigger	32" (812mm)	3 1/2" (89mm)

What if your pipe or covering outside diameter is less than 3/4 inch or 19 mm?

In cases where it is difficult to label a pipe or covering due to size, we advise using durable and long-lasting energy source valve tags or custom blank tags in place of pipe labels or markers.