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Safety Sign Colors, Signal Words and Pipe Marking Color Reference

Use this reference to check that the signs, color codes and pipe labels in your plant mean what workers expect. It lists the ANSI Z535 signal words, the OSHA safety colors and the common ASME A13.1 pipe marking colors in one searchable table.

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System	Header or fluid	Color	Meaning	Typical plant use
ANSI Z535 sign header	DANGER	Red	Hazard that will result in death or serious injury if not avoided	High voltage, open hazards without guards
ANSI Z535 sign header	WARNING	Orange	Hazard that could result in death or serious injury	Moving parts, pinch points, hot surfaces
ANSI Z535 sign header	CAUTION	Yellow	Hazard that could result in minor or moderate injury	Wet floor, uneven surfaces
ANSI Z535 sign header	NOTICE	Blue	Information not related to personal injury, such as property damage or policy	Keep gate closed, restricted area policy
ANSI Z535 sign header	SAFETY INSTRUCTIONS	Green	General safety procedures and equipment locations	First aid, eyewash, emergency shower, safety equipment
ANSI Z535 sign header	Fire safety	Red	Fire equipment location and fire related instructions	Extinguisher, fire alarm pull station, hose cabinet
OSHA 1910.144 safety color	Red	Red	Fire protection equipment, danger, emergency stop devices	Emergency stop buttons, fire extinguisher stations, safety cans for flammables
OSHA 1910.144 safety color	Yellow	Yellow	Caution and physical hazards	Striking against, stumbling, falling, tripping, caught in between
OSHA 1910.144 safety color	Orange	Orange	Dangerous parts of machines or energized equipment	Inside of guards and enclosure doors, exposed gears and cutters
OSHA 1910.144 safety color	Blue	Blue	Caution limited to warning against starting or use of equipment under repair	Blue tag at control point of equipment being serviced
OSHA 1910.144 safety color	Green	Green	Safety and first aid equipment location	First aid kit, eyewash, safety exit signs in some regions
OSHA 1910.144 safety color	Purple (magenta) on yellow	Purple and yellow	Radiation hazard	Radiography area, X-ray cabinets, radiation sources
OSHA 1910.144 safety color	Black and white	Black, white	Traffic and housekeeping markings	Aisle borders, waste container markings
ASME A13.1 pipe marking	Water (potable, cooling, boiler feed)	Green	Water service	Cooling water loops, process water
ASME A13.1 pipe marking	Fire quenching fluids	Red	Fire protection service	Sprinkler mains, standpipes, fire water
ASME A13.1 pipe marking	Compressed air	Blue	Compressed air service	Plant air headers and drops
ASME A13.1 pipe marking	Combustible fluids	Brown	Combustible but not flammable fluids	Fuel oil, hydraulic fluid, lubricants
ASME A13.1 pipe marking	Flammable or oxidizing fluids	Yellow	Flammable or oxidizing service	Natural gas, solvents, oxygen
ASME A13.1 pipe marking	Toxic and corrosive fluids	Orange	Toxic or corrosive service	Acids, caustics, plating line chemicals
Facility floor marking (common practice)	Aisles and walkways	Yellow or white	Traffic lanes and walking routes	Forklift aisles, pedestrian walkways
Facility floor marking (common practice)	Hazard area stripes	Red and white or black and yellow	Do not block or caution zone	Fire equipment clearance, electrical panel clearance

Sign headers follow ANSI Z535.2 and OSHA 1910.145 practice, safety colors follow OSHA 1910.144, and pipe colors follow ASME A13.1 guidance. Floor marking colors vary by site standard. Verify against the edition your site has adopted.

Signage and inspection records in one system

Optional: a short chat on how safety inspections can be tied to locations and work orders in your ERP.

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How to use the table

Search by color, header word or fluid. When auditing signs, walk an area with the list and check that the header word matches the severity of the hazard, for instance that a Danger header is not used where the risk is only minor injury. For pipes, compare the band color and the legend to the fluid in the line. Export the rows to Excel and add columns for location and corrective action.

Signal words and severity

ANSI Z535 ties each header to a level of risk. Danger means the hazard will cause death or serious injury if not avoided. Warning means it could. Caution means minor or moderate injury. Notice is for non-injury matters. Overusing Danger weakens it, because workers learn to ignore signs they see everywhere. Pick the header from a risk assessment, not from habit.

Danger: red, imminent, severe
Warning: orange, possible, severe
Caution: yellow, possible, minor or moderate
Notice: blue, no personal injury
Safety instructions: green, how and where

Common problems found in audits

Mixed old and new signs on the same machine, text-only signs for a mixed-language workforce, pipe markers hidden behind insulation or missing flow arrows, and floor markings worn out where forklifts cross. Consider pictograms and the languages your workers read. Keep a list of sign locations and replace faded signs on a schedule.

Frequently Asked Questions

What is the difference between a Danger and a Warning sign?

Danger signals a hazard that will cause death or serious injury if not avoided, and uses a red header. Warning signals a hazard that could cause death or serious injury, and uses an orange header. Caution is for minor or moderate injury.

Are pipe marking colors mandatory?

ASME A13.1 is a consensus standard. OSHA references it as accepted practice in some places and many insurers and local codes expect it. Sites often adopt it formally in their own standards for consistency.

What does a blue tag mean?

Under OSHA safety color practice, blue marks caution against starting or using equipment under repair. Many plants use blue tags for out-of-service equipment. Lockout tagout tags are a separate control with their own rules.

Does this replace the standards?

No. It is a summary for quick checks. Use the current edition of ANSI Z535, OSHA 1910.144 and 1910.145, and ASME A13.1 for final design of signs and markings.

If you track signage, inspection dates or corrective actions in your ERP or maintenance system, we can show how to connect them to locations and work orders.

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