Fire Extinguisher Selection by Hazard: Class A, B, C, D and K Lookup
This table connects real plant hazards to the extinguisher class and agent that suits them, and lists what to avoid. It is meant for walk-through audits, fire warden training and checking that the extinguishers in a department match what is actually stored there.
| Hazard or location | Fire class | Suitable agent | Avoid | Note |
|---|---|---|---|---|
Paper, cardboard, packaging | A | Water, ABC dry chemical, foam | None specific | Typical warehouse and packing area |
Wood pallets and dunnage | A | Water, ABC dry chemical | None specific | Check for deep-seated embers after knock-down |
Textiles, rags, wipers | A | Water, ABC dry chemical | None specific | Oily rags may self-heat, use closed metal bins |
Diesel, fuel oil, hydraulic oil | B | ABC or BC dry chemical, CO2, foam | Straight water stream | Water can spread the burning liquid |
Paint, solvents, thinners | B | BC or ABC dry chemical, CO2, foam | Straight water stream | Paint booths often have fixed suppression too |
Cutting oil and machine tool coolant mist | B | ABC dry chemical, CO2 | Straight water stream | Many CNC machines fit an internal suppression system |
Flammable gas leak (propane, acetylene) | B | Shut off supply first, then dry chemical | Extinguishing without isolating the gas | A burning gas leak can re-ignite explosively |
Electrical panels and switchgear | C | CO2, clean agent, ABC or BC dry chemical | Water, foam | De-energize if safe, dry chemical can foul contacts |
Server room and control room electronics | C | CO2 or clean agent (halocarbon) | Water, dry chemical powder | Clean agents leave no residue |
Motors, transformers, VFD cabinets | C | CO2, clean agent, dry chemical | Water | Oil-filled transformers are also a class B hazard |
Forklift charging area (lead acid) | A, B, C | ABC dry chemical, CO2 | Water on live chargers | Check ventilation and eyewash too |
Magnesium chips and swarf | D | Class D dry powder, dry sand | Water, CO2, ABC dry chemical | Magnesium burns violently with water |
Titanium chips and turnings | D | Class D dry powder | Water, CO2, ABC dry chemical | Keep fine chips separated from coolant |
Aluminum powder and fine dust | D | Class D dry powder | Water, CO2 | Dust explosion risk, see NFPA 484 and 652 |
Sodium, potassium, lithium metal | D | Class D agent specified by the maker | Water, CO2 | Check the SDS for the specified powder |
Deep fat fryer and canteen kitchen | K | Wet chemical | Water, ABC dry chemical alone | Hood suppression system is usually required |
Lithium-ion battery packs | A (cells), C (electrical) | Large volumes of water or water mist as per the maker guidance | Relying on a small extinguisher | Extinguisher ratings do not cover thermal runaway |
Welding and hot work area | A, B | ABC dry chemical, water can near work | None specific | Hot work permit and fire watch also apply |
Spray paint booth | B | Fixed dry chemical or CO2 system, BC portable | Water | Overspray residue is a fire load |
General guidance only. Extinguisher selection, quantity, spacing and inspection must follow your local fire code, NFPA 10 or equivalent national standard, and the insurer's survey. Letter K is a US class, the equivalent cooking oil class is F in the UK, EU and Australia.
Inspection due dates inside your ERP
Optional: we can outline how extinguisher and safety equipment inspections can be scheduled from your ERP or EAM.
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How to use it on a floor walk
Walk a department, list the materials and equipment, and search for each one. Note the class letters that appear. Then compare against the extinguisher labels on the wall: the letter and the agent must match the hazard. Record gaps such as a water extinguisher near a switchgear room or no class D powder in a machining cell that cuts titanium. Export the table to Excel to attach it to your inspection record.
What the classes mean
Class A covers ordinary combustibles. Class B covers flammable liquids and gases. Class C is energized electrical equipment, and the class label really means the agent is non-conductive. Class D is combustible metals and needs a special powder. Class K (US) or F (UK, EU, Australia) covers cooking oils and fats. Multipurpose ABC dry chemical extinguishers cover A, B and C but are wrong for metal fires and kitchens.
- Water: class A only, never on B, C or D
- CO2: B and C, no residue, limited reach and little cooling
- ABC dry chemical: A, B and C, corrosive residue on electronics
- Class D powder: metals only, specific to the metal
- Wet chemical: kitchen fat fires
Mistakes to avoid
Do not assume one extinguisher type fits the whole plant. A common finding is only ABC units in a machining area with magnesium or titanium. Another is blocked or unmounted units, or units past their monthly check. Training matters too: untrained staff should evacuate and raise the alarm. Under OSHA 29 CFR 1910.157 an employer that expects employees to use extinguishers must provide training at hire and annually.
Frequently Asked Questions
Can I use an ABC extinguisher on an electrical fire?
Yes, ABC dry chemical is rated for class C. The powder is corrosive and can damage electronics and contacts, so for server rooms and sensitive equipment CO2 or a clean agent is the better choice.
What extinguisher is right for metal shavings?
A class D dry powder extinguisher suited to the metal, or dry sand where allowed. Water, CO2 and ABC dry chemical can make metal fires worse. Check the safety data sheet and the powder maker's listing.
Do extinguishers work on lithium-ion battery fires?
Not reliably. Small extinguishers may knock down flames but cannot stop thermal runaway. Guidance from most makers is to cool with large amounts of water or water mist and to evacuate. Follow your site risk assessment.
How often must extinguishers be inspected?
Under NFPA 10 and OSHA 1910.157 portable extinguishers get a monthly visual check, an annual maintenance check with a tag, and periodic hydrostatic testing at intervals set by the type. Confirm the details with your local code.
If you want hazard, location and inspection due dates linked to assets in your maintenance system, we can help set that up as part of an ERP or EAM project.
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