Warning sign (yellow triangle)
A yellow triangle with a black border and a black pictogram warns of a hazard. With an exclamation mark inside, it is the general warning sign.
Easily confused with
- WARNING signThe 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.
- CAUTION signThe lowest of the three hazard signal words. CAUTION, in black on yellow, marks a hazard that could result in minor or moderate injury if it is not avoided.
- Exclamation mark (GHS07)GHS pictograms are red-bordered diamonds, ISO warning signs yellow triangles.
How to read it
ISO 3864-1 defines a warning sign as one that indicates “a specific source of potential harm”, and gives it an equilateral triangle with rounded corners, yellow with a black symbol. ISO 7010 numbers warning signs with a W: W001 is the general warning sign, W002 explosive material, W003 radioactive material or ionizing radiation, W004 laser beam. Great Britain’s 1996 regulations call the general sign “General danger” and require the yellow to take up at least half the sign. The pictogram names the hazard; the biohazard, radiation, electricity and laser triangles have pages of their own.
Also searched as: iso 7010 warning, yellow warning triangle.
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.
Warning signs in the British regulations
The 1996 regulations list flammable material or high temperature, explosive material, toxic material, corrosive material, radioactive material, overhead load, industrial vehicles, danger: electricity, general danger, laser beam, oxidant material, non-ionizing radiation, strong magnetic field, obstacles, drop, biological risk and low temperature. A further sign, harmful or irritant material (a black cross), was removed after the 2015 changes to chemical labelling law, HSE’s guidance says.
What are lab safety symbols?
Lab safety symbols are the signs on laboratory doors, and they come from several systems at once. Kansas State University’s lab signs carry the GHS pictograms for the chemicals present, outlined in red with a black image; the NFPA 704 fire diamond; and symbols for cryogens, loud noise, radioactive material and lasers. The University of Houston’s signs add the protective equipment needed for entry, drawn as PPE symbols.
Look-alikes
The GHS pictograms on chemical labels are red-bordered diamonds. On American signs, a triangle with an exclamation mark sits beside the signal word as ANSI’s safety alert symbol, part of a DANGER, WARNING or CAUTION header. The warning triangle in Britain’s Highway Code is something else again: a triangle put on the road behind a broken-down vehicle.
More safety signs
Browse symbols drawn with triangles.
Sources
- 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, 3.16, Table 1
- ISO 7010:2011, Graphical symbols — Safety colours and safety signs — Registered safety signs (preview), ISO 7010:2011, International Organization for Standardization, preview via iTeh Standards, 4.3, Table 2
- The Health and Safety (Safety Signs and Signals) Regulations 1996, Schedule 1, SI 1996/341, legislation.gov.uk (UK Government), Part II, 3.2
- Safety signs and signals: The Health and Safety (Safety Signs and Signals) Regulations 1996, Guidance on Regulations, L64 (third edition, 2015), Health and Safety Executive (Great Britain), paragraphs 4, 48
- K-State Laboratory Signs, Kansas State University Environmental Health and Safety
- Laboratory Doorsigns, University of Houston Environmental Health and Safety
- Product Safety Signs and Labeling: ANSI Z535.4-2023, The ANSI Blog, American National Standards Institute
- The Highway Code: Breakdowns and incidents (274 to 287), Rule 274, Department for Transport (GOV.UK), Rule 274
Last reviewed September 30, 2026 by Rory Hansen. How we research