Safety Signage: OSHA Requirements, ANSI Z535 Color Standards, and Common Violations

Walk through enough facilities during an OSHA inspection and you’ll see the same signage problems over and over. Faded CAUTION signs on overhead cranes that should say DANGER. Handwritten paper signs taped to energy control points instead of proper lockout tags. PPE-required areas with no signage at all. These aren’t small housekeeping items. Inadequate safety signs get cited, and depending on the hazard involved, they can become willful violations.

Two standards govern most of this: OSHA 1910.144 for color coding and 1910.145 for accident prevention signs and tags. ANSI Z535 runs alongside them as the recognized industry benchmark.

OSHA 1910.144 and 1910.145: The Regulatory Foundation

OSHA 1910.144 sets color requirements for safety equipment and hazards in general industry. The rule is short and specific. Red identifies fire protection equipment, danger, and safety can caps for flammable liquids. Yellow marks physical hazards including strike-against hazards, stumbling hazards, and caution areas. Orange covers dangerous parts of machines, energized electrical equipment, and construction warning signs.

OSHA 1910.145 goes further. It covers the design, application, and use of accident prevention signs and tags. Under this standard, signs fall into four categories: danger signs, caution signs, safety instruction signs, and general notice. Each has specific color and format requirements.

Danger signs must be red, black, and white. The word DANGER must appear in the red panel. Caution signs must be yellow with black lettering. The word CAUTION must be prominent. Safety instruction signs, which give required or recommended procedures, must use white or green backgrounds with white lettering on green panels.

The standard also specifies that tags, which are temporary warnings, must be used whenever a hazard exists that isn’t covered by a permanent sign. Tags stay in place until the hazard is corrected or controlled.

ANSI Z535: The Practical Standard

ANSI Z535 is a voluntary standard published by the American National Standards Institute. It builds on OSHA’s requirements with a more complete system covering signal words, colors, symbols, and layout. OSHA inspectors treat it as the benchmark for evaluating sign adequacy.

The ANSI Z535 family covers several sign types. Z535.1 covers safety colors. Z535.2 covers environmental and facility safety signs (the most commonly referenced). Z535.4 covers product safety signs and labels.

The biggest thing ANSI Z535 adds to the OSHA framework is the signal word hierarchy.

The Signal Word Hierarchy

ANSI Z535 defines five signal words, each corresponding to a specific severity level. Getting this right matters more than almost any other signage decision.

DANGER signals an imminently hazardous situation that will result in death or serious injury if not avoided. This word is reserved for the highest-severity hazards. Energized electrical panels above 480 volts, unguarded openings that lead to fatal falls, and similar conditions get DANGER signs.

WARNING signals a potentially hazardous situation that could result in death or serious injury. The distinction from DANGER is immediacy and certainty. DANGER says “this will kill you if you ignore it.” WARNING says “this could kill you under the wrong conditions.”

CAUTION signals a hazard that may result in minor or moderate injury, or property damage. Slippery floors, low clearance overhead beams, and minor trip hazards typically get CAUTION. The key word is “minor or moderate.” Using CAUTION for a condition that can cause death is a serious mismatch.

NOTICE is not a safety signal word. It indicates information that isn’t related to a personal injury hazard. Operational procedures, equipment information, and workplace rules go on NOTICE signs. The panel is blue with white lettering.

SAFETY INSTRUCTION signs provide general safety practices and instructions not associated with a specific hazard. Green backgrounds with white lettering. These are appropriate for safety reminder messages posted in common areas.

The practical rule: match the signal word to what actually happens if a worker ignores the sign. If the realistic outcome is a fatality, use DANGER. If it’s a serious injury, use WARNING. If it’s a sprain or a scratch, CAUTION is appropriate.

When Signs Are Legally Required

OSHA doesn’t have a single standard that says “put a sign here.” The requirements are distributed across dozens of standards, each mandating signage for specific hazards.

The PPE standard at 1910.132(d)(2) requires that areas where PPE is required be identified by signs or equivalent means. If workers must wear hard hats in a construction zone within your facility, that area needs posted notification.

The lockout/tagout standard at 1910.147 requires DANGER signs or equivalent warnings on equipment undergoing energy control procedures. Tags used in lockout programs must comply with 1910.145(f) requirements for accident prevention tags.

The permit-required confined space standard at 1910.146(c)(2) requires warning signs at each permit space informing workers of the hazard and the requirement to have authorization before entering.

The radiation standard at 1910.1096 requires specific warning signs at radiation areas, high-radiation areas, and airborne radioactivity areas, with mandatory symbols and signal words.

Beyond these specific standards, the General Duty Clause of the OSH Act (Section 5(a)(1)) creates a broader obligation. If a recognized hazard exists that isn’t obvious to workers, an employer has a General Duty obligation to warn of it. OSHA uses this to cite signage failures in situations where a specific standard doesn’t mandate a sign but the hazard is real and recognizable.

Placement, Visibility, and Lighting

A sign nobody can see isn’t a sign. OSHA 1910.145 requires that signs be placed to be visible to all affected employees in the hazard area. The standard doesn’t specify heights or distances, but the intent is clear: workers must be able to read and act on the warning before they reach the hazard.

The practical requirements that come out of inspections and enforcement:

Signs need to be visible from the approach to the hazard, not just from within it. A sign placed inside a doorway only seen after you’ve already entered doesn’t satisfy the intent of 1910.145.

Lighting matters. A sign that’s properly placed but unreadable in low light conditions doesn’t meet the standard. In areas with reduced lighting, consider reflective materials or additional illumination.

Height should position the sign at eye level or slightly above for the typical worker. Overhead signs need to be large enough to read at the viewing distance. Tiny signs mounted eight feet up don’t communicate the hazard.

Don’t block signs. This is common in storage areas where product or equipment gradually obscures hazard warnings. Include sign visibility in your periodic facility inspections.

Sign Maintenance and Inspection

Signs degrade. UV exposure fades colors, which matters because color is part of the safety message. A DANGER sign that’s faded to pink no longer communicates effectively. Chemical exposure, moisture, and physical damage all degrade sign readability.

Include safety sign inspection in your routine facility inspection process. Look for fading, damage, signs that have been covered, and signs that no longer match the current hazard configuration. Signs should be replaced before they become unreadable, not after.

Signs placed during construction or temporary operations need to be updated when conditions change. A CAUTION: WET FLOOR sign left in place after the floor dried isn’t just useless, it conditions workers to ignore signs in that area.

Tags vs. Signs: Understanding the Difference

Safety tags are temporary. Signs are permanent or semi-permanent. The distinction matters for both program design and compliance.

Tags under 1910.145(f) must include a signal word (DANGER, CAUTION, or BIOHAZARD), a major message explaining the specific hazard, an instruction message if needed, and a means of attachment that makes the tag conspicuous. Tags must be legible and understandable to all workers who might encounter them.

In lockout/tagout programs, tags are attached to energy isolating devices during lockout. They warn other workers that the equipment is being serviced. But OSHA is clear: a tag alone is not an energy control. The tag communicates the hazard. The lockout device controls it.

Tags are not a substitute for permanent signs on ongoing hazards. If a hazard is going to exist in a location for more than a few days, it needs a proper sign.

Pictograms and Multilingual Workforces

If your workforce includes workers with limited English proficiency, text-only signs create a gap. A DANGER sign with English text only may not communicate effectively to a worker who reads Spanish or Vietnamese.

ANSI Z535 supports the use of safety symbols and pictograms alongside or instead of text. ISO-compliant safety symbols are internationally recognized and don’t require reading ability in any specific language. Combining signal words, symbols, and multi-language text is the safest approach for mixed-language facilities.

OSHA has cited facilities for signage failures in multilingual workplaces under the General Duty Clause. If your workforce includes significant numbers of workers who can’t read English and your signs are English-only, that’s a recognized hazard.

For facilities onboarding new employees, addressing signage comprehension is a natural part of new employee safety orientation. Workers should be shown all relevant signs in their work area and confirm they understand what each one means.

Common Violations

The citations that show up repeatedly in OSHA data for signage involve four situations: missing required signs where a specific standard mandates them, wrong signal word for the actual hazard severity, signs too faded or damaged to read, and absence of any signage in areas where the General Duty Clause creates an obligation to warn.

Homemade signs are a consistent problem. A handwritten note on a piece of cardboard that says “watch out” doesn’t meet 1910.145. If you need a sign, buy one that meets OSHA 1910.145 requirements and ANSI Z535 formatting.

Spec your signs to ANSI Z535. Buy from a reputable safety supply vendor who sells compliant products. Use signal words that match actual hazard severity. Check signs during every facility walkthrough. That approach eliminates virtually every signage citation before the inspector walks through the door.