WARNING sign
The middle signal word on a safety sign. WARNING, in black letters on orange, marks a hazard that could result in death or serious injury if it is not avoided.
Easily confused with
How to read it
ANSI Z535 grades hazards with three signal words. WARNING covers the same outcome as DANGER, death or serious injury, as something that could happen where DANGER says it will; CAUTION is for minor or moderate injury. The orange is specified to stay clear of its neighbours. Angela Lambert, who chairs the ANSI Z535.1 safety colours subcommittee, told In Compliance Magazine that it “can’t look like ‘yellowish orange’ or ‘reddish orange’”, so that it isn’t mistaken for caution yellow or danger red.
Also searched as: ansi warning, warning signal word.
These explain what a sign’s signal word, colour and shape mean. For what to do in a hazard area, follow the site’s own signs, instructions and trained staff.
Danger, warning, caution and notice compared
| Signal word | Colours in ANSI Z535 | What it signals |
|---|---|---|
| DANGER | White letters on red | A hazardous situation that will result in death or serious injury if not avoided |
| WARNING | Black letters on orange | A hazardous situation that could result in death or serious injury if not avoided |
| CAUTION | Black letters on yellow | A hazardous situation that could result in minor or moderate injury if not avoided |
| NOTICE | White italic letters on blue | Practices not related to physical injury |
WARNING in OSHA’s rules
OSHA’s general sign rule, 29 CFR 1910.145, classifies signs as danger, caution and safety instruction signs, and has no warning sign. WARNING appears there only on tags, which may be used for a hazard level between “Caution” and “Danger”. Signs made to ANSI Z535.2, which includes WARNING, have been accepted under OSHA’s sign rules since 2013.
Look-alikes
The triangle with an exclamation mark beside the word is the safety alert symbol, which ANSI describes as “an equilateral triangle surrounding an exclamation mark”. ANSI’s summary of its product-label standard gives the WARNING version as a black triangle with an orange exclamation mark. The ISO general warning sign looks similar but stands on its own, as a yellow triangle with a black border.
More safety signs
Browse symbols drawn with letters and numbers, squares and rectangles or triangles.
Sources
- Product Safety Signs and Labeling: ANSI Z535.4-2023, The ANSI Blog, American National Standards Institute
- ANSI Z535.1 – Safety Colors in Focus, Erin Earley, “On Your Mark” column, 1 July 2023, In Compliance Magazine
- Specifications for accident prevention signs and tags (29 CFR 1910.145), 29 CFR 1910.145, U.S. Occupational Safety and Health Administration, 1910.145(c), (f)(7)
- Updating OSHA Standards Based on National Consensus Standards; Signage, 78 FR 35559 (13 June 2013), direct final rule, U.S. Occupational Safety and Health Administration, via the Federal Register
- ISO 3864-1:2011, Graphical symbols — Safety colours and safety signs — Part 1: Design principles for safety signs and safety markings (preview), ISO 3864-1:2011, International Organization for Standardization, preview via iTeh Standards, Table 1
- The Health and Safety (Safety Signs and Signals) Regulations 1996, Schedule 1, SI 1996/341, legislation.gov.uk (UK Government), Part II, 3.2
Last reviewed September 30, 2026 by Rory Hansen. How we research