Free Pipe Marking Label Generator (ASME A13.1)

A pipe marking label (pipe marker) identifies the contents of a pipe and the direction of flow, using a standardized color code so workers, contractors, and emergency responders can recognize the hazard at a glance. The governing standard in the United States is ASME A13.1 — Scheme for the Identification of Piping Systems. A compliant marker has three parts: a colored background that signals the hazard category, a legend naming the contents in uppercase letters sized to the pipe diameter, and a flow-direction arrow.

ASME A13.1 prescribes six standard color combinations: yellow background with black letters for flammable or oxidizing fluids; brown with white letters for combustible fluids; orange with black letters for toxic or corrosive fluids; red with white letters for fire-quenching fluids (sprinkler and deluge lines); green with white letters for potable, cooling, boiler feed, and other water; and blue with white letters for compressed air. Four more combinations — purple/white, white/black, gray/white, and black/white — are reserved for user-defined, site-specific services.

There is no single general OSHA standard that says "label every pipe," and OSHA's Hazard Communication Standard (29 CFR 1910.1200) actually exempts pipes from its container-labeling rules. But that is not the end of the story: specific OSHA standards do require A13.1-style marking (for example 1910.253 for oxygen–fuel gas piping), OSHA can and does cite unmarked hazardous lines under the General Duty Clause, and fire codes, mechanical codes, insurers, and auditors all expect ASME A13.1 marking. A13.1 is the national consensus standard an inspector will measure your facility against.

ASME A13.1 sizes the marker to the pipe. For an outside diameter (including insulation) of ¾″ to 1¼″, the color field must be 8″ long with ½″ letters; 1½″ to 2″ pipe needs 8″ with ¾″ letters; 2½″ to 6″ pipe needs 12″ with 1¼″ letters; 8″ to 10″ pipe needs 24″ with 2½″ letters; and pipe over 10″ needs a 32″ field with 3½″ letters. This generator applies the correct size automatically when you select the pipe diameter.

Yes. ASME A13.1 requires the direction of flow to be indicated with an arrow at the marker. If the line can flow in both directions, use arrows pointing both ways. This generator prints the arrow as part of the marker — left, right, or bidirectional.

Place markers adjacent to every valve and flange, at every change of direction, on both sides of wall, floor, or ceiling penetrations, next to the equipment the line serves, and at intervals on straight runs — every 25 to 50 feet is the accepted practice. Position each marker for the normal line of sight: below the horizontal centerline on overhead pipes viewed from the floor.

The split follows flash point, the same line the fire codes draw. Flammable fluids — those that ignite at ambient temperatures, such as natural gas, propane, hydrogen, and gasoline — take a yellow marker with black letters (oxidizers share yellow). Combustible fluids — those that must be heated above their flash point, such as diesel, fuel oil, and lubricating oil — take a brown marker with white letters. Brown/combustible was added in the 2015 revision of A13.1, so older facilities often show these lines incorrectly in yellow.

Download the PDF at the correct A13.1 size for your pipe and print at 100% / actual size — never "fit to page," which shrinks the mandated letter height. For dry indoor lines, a color print laminated or inserted in a clear label sleeve works. For process areas, outdoor runs, or anything exposed to washdown, UV, or chemicals, print on self-adhesive vinyl or polyester stock — or hand the PDF to a sign shop as the exact artwork to produce. The 8″ and 12″ sizes fit letter and legal paper in landscape; the 24″ and 32″ sizes are wide-format jobs.

ASME A13.1 recognizes that very small lines cannot carry a legible marker. For pipes under ¾″ outside diameter, use a permanently attached identification tag — a stamped or engraved tag at valves and outlets — instead of a wrap-around marker.

Yes. Generate as many ASME A13.1 pipe markers as you need with no account and no payment. A valid work email is required to download the print-ready PDF.