Owner's manuals are full of boxed warnings, and after the first dozen most people stop reading them. That's understandable, but the words at the top of each box are chosen deliberately. They tell you how serious the hazard is, and knowing the scale makes it much easier to spot the few that really matter.
The signal words
In the US, most manufacturers follow the ANSI Z535 standard, and international products follow a similar approach from ISO 3864. Both use a small set of signal words, from most to least serious.
| Signal word | What it means | Typical color |
|---|---|---|
| DANGER | A hazard that will cause death or serious injury if not avoided | Red |
| WARNING | A hazard that could cause death or serious injury | Orange |
| CAUTION | A hazard that could cause minor or moderate injury | Yellow |
| NOTICE | Information about property damage, not personal injury | Blue |
The difference between DANGER and WARNING is certainty. DANGER is for situations like working on live electrical parts, where the outcome is not in doubt.
Symbols you'll see often
- Triangle with an exclamation mark: the general safety alert symbol. Read the text next to it.
- Lightning bolt in a triangle: electrical shock hazard.
- Book with an "i": read the manual before use.
- Flame: fire or flammable material.
- Wavy lines over a surface: hot surface.
- Crossed-out wheelie bin: don't throw in household trash. The product needs electronics recycling.
- Square inside a square: double insulated, so no ground connection is needed.
Which warnings to actually read
You don't need to memorize every box. But always read the DANGER and WARNING sections before installing, wiring, or doing maintenance on anything that uses gas, high voltage, blades or pressure. For baby products and car seats, the warnings contain the limits that keep a child safe, and they change between models.