Workshop Safety: PPE, Fire Classes, Lifting and Shop-Floor Codes
This domain tests how a workshop protects people and machines: personal protective equipment, fire classification and extinguisher choice, safe jacking and lifting, and the colour codes painted on shop floors and equipment.
Personal protective equipment
Safety boots with steel toes, goggles when grinding, chiselling or handling battery acid, gloves (removed near rotating shafts so they cannot snag), apron, ear plugs in the engine test bay, and a welding shield for arc work. Remove rings, watches and loose sleeves; tie back long hair. Never use compressed air to clean dust off skin or clothing - it can force air into the tissues.
Fire classes and extinguishers
Every fire needs three things: fuel, oxygen and heat. Remove any one and it goes out. Class A solids (wood, paper, rags) - water or foam. Class B flammable liquids (petrol, diesel, paint thinner) - foam, dry powder or CO2. Class C gases - dry powder, shut off the supply. Class D metal fires - special dry powder only. Live electrical equipment - CO2 or dry powder, never water. Petrol floats on water, so water spreads a petrol fire instead of extinguishing it.
Lifting, jacking and equipment
A jack lifts; it does not support. Always place axle stands under the frame or axle and chock the wheels before going underneath. Check the guard on a bench grinder and ring-test the wheel before fitting. Engine exhaust contains carbon monoxide, so run engines only with the door open or an extractor running. Battery charging releases hydrogen - no sparks or smoking nearby.
Worked example
A mechanic spills petrol near a hot exhaust and a small flame appears. Reasoning: fuel, oxygen and heat are all present, and the fuel is a Class B liquid. Correct action is to stop the engine, switch off the ignition, and smother the flame with foam, dry powder or CO2. Water is the wrong choice because petrol is lighter than water and would float, carrying the burning fuel across the floor.
Traps that cost marks
Choosing water for an electrical or petrol fire; supporting a vehicle on a jack alone; forgetting wheel chocks; wearing loose clothing near a propeller shaft or grinder; ignoring the correct extraction of exhaust gas in a closed shed.