Does OSHA require pipes to be labeled, marked, or colored (a.k.a., pipe labels, pipe labeling, or pipe markers)?

Specific pipe labeling, marking, and coloring regulations

Federal OSHA does not require pipes in the workplace to be labeled, marked, or colored, other than in:

• Processing plants where the pipes contain flammable liquids (see 29 CFR 1910.106(h)(4)(ii)(c)),
• Certain welding situations (see 1910.253(d)(4)(ii)),
• Textile situations (see 1910.262(c)(7)), or
• Pulp, paper, and paperboard mills (see 1910.261(a)(3)(ii)).

However, also see information about safety color codes and sign and tag requirements for pipes later in this Frequently Asked Question.

Scheme for the identification of piping systems

It’s important to know that American National Standards Institute (ANSI) A13.1-1956, Scheme for the Identification of Piping Systems, is referenced at the following OSHA general industry regulations. Therefore, these are the only instances when the ANSI A13.1 color scheme is required by OSHA, that we know of. If you fall under these regulations, you will need to follow the 1956 edition of ANSI A13.1 when marking pipes:

• 1910.253(d)(4)(ii) (certain welding situations),
• 1910.261(a)(3)(ii) (certain pulp, paper, and paperboard mill situations), and
• 1910.262(c)(7) (certain textile situations).

If the ANSI A13.1-1956 references do not apply to your situation and your state does not have additional requirements (check your state requirements), you may wish to instead use the standards recommended by the 1996 or 2020 editions of ANSI A13.1. Both editions concern contents of pipes transporting not just liquids but also semi-liquids, gases, or fine particulates at industrial and commercial facilities, institutions, and public assembly buildings. The 2020 edition has a different color scheme than the 1996 and earlier editions.

Voluntary consensus standard ANSI A13.1-1996 suggests that pipes be identified as follows:

• Materials of inherently low hazard and classified as gas or gaseous mixture shall have a blue label with white letters;
• Materials of inherently low hazard and classified as liquid or liquid admixture shall have a green label with white letters;
• Materials inherently hazardous and classified as flammable or explosive, chemically active or toxic, extreme temperatures or pressures, or radioactive shall have a yellow label with black letters; and
• Fire quenching materials that are classified as water, foam, carbon dioxide, halon, etc. shall have a red label with white letters.

However, voluntary ANSI A13.1-2020 suggests pipes be identified as follows:

• Compressed air markings shall have white letters on a blue background;
• Water (potable, boiler, or cooling) markings shall have white letters on a green background;
• Combustible fluid markings shall have white letters on a brown background;
• Flammable markings shall have black letters on a yellow background;
• Oxidizing fluid markings shall have black letters on a yellow background;
• Toxic fluid markings shall have black letters on an orange background;
• Corrosive fluid markings shall have black letters on an orange background;
• Fire quencher (CO₂, foam, or water) markings shall have white letters on a red background;
• Other materials markings shall have other color combinations (i.e., white letters on a purple, grey, or black background or black letters on a white background) as determined by the facility; and
• Abandoned piping markings should have black letters on a white background with a black border. The legend should also mention any pressurized fluid or residual materials remaining in the abandoned piping.

ANSI A13.1-1996 and ANSI A13.1- 2020 call for pipe markings to include the identity of the materials in the pipe and an arrow(s), as well as any other information to alert the marking observer to any other hazards, e.g., pressure and temperature. Adding Globally Harmonized System (GHS) product identifier, pictogram(s), signal word, and/or hazard statements is optional as part of the legend. In addition to the color and legend provisions, the standards offer legend examples, definitions, and further provisions on marking locations and intervals, marking approaches, the size and style of marking letters, marking visibility, and alternatives to the marking scheme itself.

Safety color codes

Again, other than the federal OSHA requirements mentioned earlier, pipes are not required to be color coded. However, be aware that 1910.144, Safety Color Code for Marking Physical Hazards, references safety colors yellow and red and what those colors identify or designate. With regard to piping, 1910.144 states that red shall be the basic color not only for the identification of danger but also for fire protection equipment and apparatus, i.e., sprinkler piping. So, for example, if you apply color to fire protection piping for identification, you must use red.

In addition to OSHA regulations, the voluntary consensus standard, ANSI Z535.1-1998, Safety Color Code, recommends the following color designations:

• Red — Fire protection equipment, danger, flammable liquid, and stop (including emergency stop buttons);
• Orange — Warning, machine parts that may cause injury, and exposed parts;
• Yellow — Warn against potential hazards, caution against unsafe acts, physical hazards (i.e., striking against, stumbling, falling, tripping, and caught in between), flammable materials storage, corrosives, instability, traffic designation, and housekeeping mark;
• Green — Safety equipment, first-aid, and evacuation routes;
• Blue — Safety information, personal protective equipment, and notice;
• Black — Traffic designation and housekeeping mark;
• White — Traffic designation and housekeeping mark;
• Black and white combined — Traffic designation and housekeeping mark; and
• Black and yellow combined — Traffic designation and housekeeping mark.

Note the 2002 and later editions of ANSI Z535.1 no longer contain the safety color meanings.

Accident prevention signs and tags

Be aware that federal OSHA 1910.145, Specifications for Accident Prevention Signs and Tags, goes over the use of DANGER, CAUTION, and other sign and tag formats. Note that:

• Accident prevention signs are not required on or near piping unless the specific hazards presented by the piping is of a nature such that failure to designate the hazard (failure to designate in the form of a sign) may lead to accidental injury to workers or the public, or both, or to property damage.
• Accident prevention tags are not required on or near piping unless:
  • No other means of protection is provided to prevent accidental injury or illness to employees who are exposed to hazardous or potentially hazardous conditions, equipment, or operations that are out of the ordinary, unexpected, or not readily apparent; or
  • The situation falls under the Control of Hazardous Energy (Lockout/Tagout) Standard at 1910.147, and a tag is required to be placed on the piping for an operation that falls under that regulation.
• 1910.145 references portions of ANSI Z53.1-1967, Safety Color Code for Marking Physical Hazards, and ANSI Z535.1-2006(R2011), American National Standard for Safety Colors.