ANSI Color Codes for Pipe Marking

By Graphic Products Editorial Staff

ansi color code pipe example

The American National Standards Institute (ANSI) is the source for a variety of standards in use across the United States and even around the world. Some of those standards have been incorporated into law, while some have been passed to other organizations for updating and maintenance. ANSI recommendations are recognized and respected in most industries. The major ANSI standard that discusses labeling for piping systems in a facility is ANSI A13.1.

The ANSI A13.1 Standard

This standard has been revised over time, with the biggest change coming in 2007. In that edition, the old ANSI standard was combined with recommendations from the American Society of Mechanical Engineers (ASME). As a result of the cooperation between the two groups, the new standard has been called “ANSI/ASME A13.1,” or even just “ASME A13.1,” but the central goal of the standard remains the same: ensuring safety and efficiency in a facility by clearly labeling all pipes.

A big part of the new edition was a dramatic change to the color code. Before the 2007 edition, color was used to indicate whether the contents of a pipe were “high-hazard,” “low-hazard,” or part of a fire suppression system. The 2007 version introduced a more specific code that identified the type of hazard that was posed. Flammable materials, for example, would be labeled with one color, while toxic materials would be labeled with another color. Additional colors were specified for user definition, allowing flexibility for unique challenges that could arise in a facility.

The most recent edition of the standard was released in 2015. It keeps the specialized color code, expanding one category to include additional hazard types. This edition also adds an option to include hazard pictograms from the international GHS standard for even more detail.

Pipe Marking with ANSI Color Codes

The ANSI/ASME A13.1 color code uses six predefined colors and four user-defined colors. The six predefined colors identify broad types of pipe contents, with definitions given in the standard to limit confusion. The four user-defined color options can be defined separately by each facility using the standard; in this case, the definitions need to be documented in the facility, and training needs to be provided for the workers in the area.

Each category has a solid color for the label background, which may be extended to color the entire pipe if desired, as well as a high-contrast color for the text that needs to appear on the label.

Pipe Contents

Color Scheme

Fire-Quenching Fluids

White Text on Red Background

Toxic or Corrosive Fluids

Black Text on Orange Background

Flammable or Oxidizing Fluids

Black Text on Yellow Background

Combustible Fluids

White Text on Brown Background

Other Water

White Text on Green Background

Compressed Air or Other Gases

White Text on Blue Background


White Text on Purple Background


Black Text on White Background


White Text on Gray Background


White Text on Black Background

Identifying ANSI A13.1 Categories

The predefined categories rely on the definitions provided in the standard. These definitions sometimes disagree with definitions used elsewhere, so it’s important to know what terms are being used.

The most common point of confusion is between “Flammable” and “Combustible,” as those terms are defined in the ANSI/ASME standard. In the past, other standards have used flash points and volatility measurements to identify whether a material was flammable or combustible. The ANSI/ASME standard uses a simpler definition: if the material is a vapor, or produces a vapor, that could ignite and continue to burn in air, it’s considered flammable. Other materials that may pose a fire hazard are considered combustible instead.

Another common confusion is how to label pipes that fall into more than one category. For example, some flammable gases are also toxic. Which color code should be used for them? This decision is largely up to each facility, but there are two common approaches: some facilities identify one of the hazard types as more significant in their specific facility, and use the color recommended for that hazard, while other facilities use one of the user-defined color schemes to identify a particular combination of hazards.

Are ANSI Color Codes Mandatory?

While a standardized color code for pipe labeling is clearly a good idea, and OSHA has repeatedly referred to the ANSI system as a common and acceptable practice, this particular color code is not actually mandatory.

An important clause in the standard points out that the color code in the standard is a recommendation, and that other color schemes may be acceptable. In order to comply with ANSI A13.1, the color code in use in a facility must be clearly documented, and workers need to be effectively trained to recognize and understand the code in place.

This is especially important in situations where a highly specialized piping system makes the ANSI color code less effective. For example, pipes in hospitals often carry a variety of compressed gases; some are for patients to breathe, while others are for operating equipment, and others are part of an anesthetic system. Confusion across these types of pipes could be dangerous, or even fatal. As a result, hospitals typically follow a more specialized color code system.

To make sure your facility uses the code that’s best suited for its needs, request a free copy of our Best Practice Guide to Pipe Marking. If you’re ready to move forward with pipe marking in your facility, the DuraLabel line of printers from Graphic Products may be just the tools you need to make the project succeed.