What the rating code on an extinguisher actually certifies — the A number (wood crib size), B number (litres of burning liquid), class C/F marks — and how powder, CO2, foam and lithium-specific (AVD) types map to workshop, electrical, kitchen and battery risks, with the stocked Housegard range and signage.
Under EN 3, an extinguisher's rating is earned on standard test fires. The A number is the length class of a burning wood crib it extinguished (55A beats 43A beats 27A); the B number is the volume class of a burning liquid tray (233B > 183B > 89B > 34B); C marks suitability for gas fires (no numeric rating); F ratings cover fat fryers. So "Powder 6 kg 55A 233B C" certifies: large wood-crib capability, large liquid-tray capability, gas-suitable. Bigger numbers mean more extinguishing performance, not just more agent — a high-efficiency 6 kg can out-rate a mediocre 12 kg.
| Type | Classes | Stocked examples | Best placed |
|---|---|---|---|
| ABC powder | A B C | PE6HR-A 6 kg 55A 233B C, PE12HR-A 12 kg, PE2HR-A 2 kg, PE1HR-A 1 kg | Vehicles, workshops, mixed risk; highest rating per kg |
| CO2 | B (electrical practice) | 5 kg 89B, 2 kg 34B | Switchrooms, electronics, kitchens' fringe — no residue |
| Foam (PFAS-free) | A B | 6 L 27A 144B, 9 L 34A 183B | Offices, corridors: good A/B with limited mess |
| AVD (lithium) | Li-ion battery fires | AVD 6 L | Battery charging/storage areas |
| ReUse / service classes | per model | ReUse 6 kg | Sites standardising refillable stock |
Powder's drawback is collateral: a discharge in a server room or galley writes off more than the fire. CO2 near people outdoors is ineffective (wind) and in tight unventilated spaces is an asphyxiant — placement thinking, not just rating shopping.
Monthly in-house glance: in place, unobstructed, pin sealed, gauge in green, hose sound. Periodic competent-person service and the pressure-test/refill intervals follow the standard your jurisdiction applies (NS 3910 practice in Norway; the service label on the bottle is the record). After any discharge — even a second — the unit is serviced or replaced; a part-used powder never reseals reliably. Train the first-aid-fire response alongside kits and eyewash (first-aid kit Plus) so the extinguisher is the backup to evacuation, not a substitute for it.