Colours and shapes of safety signs, classes of fire and the right extinguisher for each.
Safety signs
Safety signs give a safety message quickly by shape, colour and symbol, so that even a person who cannot read the language understands it.
| Type | Shape & colour | Meaning / example |
|---|---|---|
| Prohibition | Red circle with a diagonal bar | Do not do – "No smoking" |
| Mandatory | Blue circle, white symbol | Must do – "Wear goggles" |
| Warning | Yellow triangle, black border | Be careful – "High voltage" |
| Safe condition | Green square/rectangle | Safe way – "First aid", "Exit" |
| Fire equipment | Red square/rectangle | "Fire extinguisher", "Fire alarm" |
Fire
Fire needs three things – fuel, heat and oxygen (the fire triangle). Remove any one and the fire goes out: starving (remove fuel), smothering (cut oxygen), cooling (remove heat).
Classes of fire and extinguishers
| Class | Burning material | Use |
|---|---|---|
| A | Wood, paper, cloth, cotton waste | Water, foam |
| B | Oil, petrol, paint, grease | Foam, CO₂, dry chemical powder (DCP) |
| C | Gases – LPG, acetylene | DCP (first shut off the gas) |
| D | Metals – magnesium, sodium | Special dry powder |
| Electrical | Live electrical equipment | CO₂ or DCP – never water |
Using an extinguisher – PASS Pull the pin · Aim at the base of the fire · Squeeze the handle · Sweep from side to side.
Quick Revision
- Red circle = prohibition, blue circle = mandatory, yellow triangle = warning, green = safe condition.
- Fire triangle: fuel + heat + oxygen.
- Never use water on oil or electrical fires.
- PASS: Pull, Aim, Squeeze, Sweep.
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