Classes of Fire in Singapore
Using the wrong fire extinguisher can spread flames rapidly or cause fatal electrocution. Under Singapore Standard SS 578:2019 (Code of Practice for Use and Maintenance of Portable Fire Extinguishers), fires are classified based on the type of fuel feeding the blaze.
Class A Fires (Combustible Solids)
Fuel Source: Carbon-based solid materials such as wood, paper, cardboard, fabrics, and plastics.
Characteristics: Produces glowing embers, deep-seated heat, and ash.
Extinguishing Method: Cool the burning embers below ignition temperature using Water Fire Extinguishers or Foam Fire Extinguishers, or achieve rapid surface flame knockdown using AB Dry Powder Fire Extinguisher..
Class B Fires (Flammable Liquids)
Fuel Source: Flammable and combustible liquids, including petrol, diesel, kerosene, oil-based paints, industrial thinners, and solvents.
Characteristics: Rapid surface spread; vapors ignite above the liquid surface.
Extinguishing Method: Smother the vapor layer to cut off oxygen. Foam Fire Extinguishers create an aqueous film blanket that suppresses vapors and prevents flashover; Dry Powder provides immediate flame knockdown; Carbon Dioxide Fire Extinguisher is effective for smaller, indoor contained spills leaving zero residue.
Class C Fires (Flammable Gases)
Fuel Source: Combustible gases, including Liquefied Petroleum Gas (LPG), Town Gas, butane, and methane.
Primary Response: Isolate the gas supply immediately. Turn off the main gas valve or emergency shut-off cylinder valve.
Why Extinguishers Lack a Class C Logo: Under SCDF guidelines and SS 578 (mandatory for all extinguishers certified or renewed since 1 May 2013), portable fire extinguishers in Singapore do not display a Class C marking. Extinguishing a gas flame without isolating the gas source allows invisible gas to pool, creating a catastrophic vapor cloud explosion hazard.
Electrical Hazards (Not a Standalone Class)
Under Singapore Standard SS 578:2019, electrical fires do not have a dedicated letter class because electricity is an ignition source, not a fuel. The burning components are Class A solids (wiring insulation, plastic enclosures) or Class B liquids (transformer oils).
Extinguishing Method: De-energize the power source at the main breaker if safe to do so. Use Carbon Dioxide (CO2) or Dry Powder extinguishers, which are dielectrically tested and non-conductive to eliminate shock hazards.
Class D Fires (Combustible Metals)
Fuel Source: Reactive and combustible metals, including magnesium, titanium, zirconium, lithium, potassium, and sodium.
Extinguishing Method: Use specialized Class D Fire Extinguishers. Never use water or standard foam, as hot reactive metals will break water down into hydrogen gas, triggering explosive reactions.
Class F Fires (Commercial Cooking Oils & Fats)
Fuel Source: High-temperature cooking oils, grease, animal fats, and lard in deep fat fryers and kitchen ranges.
Extinguishing Method: Deploy a Wet Chemical Fire Extinguisher or smother the pan using a Fire Blanket. Wet chemical agents extinguish the blaze via saponification, cooling the oil and creating a thick, soapy blanket that prevents re-ignition. Never throw water on hot oil.
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