BC fire extinguishers usually use Sodium bicarbonate powder. They are termed regular or ordinary fire extinguishers and can be used on class B and C fires. They were the first of the dry chemical fire extinguishers developed. The powder is usually White or blue in color.

In the heat of a fire, it releases a cloud of carbon dioxide that smothers the fire. That means the CO2 gas, which is heavier than oxygen, keeps oxygen away from the fire which then dies out. This powder is not generally effective on class A fires because the agent is expended quickly and the cloud of gas dissipates quickly so if the fuel is still sufficiently hot, the fire restarts.

While liquid and gas fires do not usually store much heat in their fuel source, solid fires (such as Class A) do retain heat and can frequently reignite.

Sodium bicarbonate was very common in commercial kitchens before the advent of wet chemical agents, but now found to be less effective than wet chemical agents for Class K (Kitchen) fires.

Though effective for BC fires, they are less effective than Purple-K for class B fires, and is NOT suitable on class A fires

What the A B C ratings mean on BC Fire Extinguishers



Fire extinguishers with a Class A rating are effective against fires involving paper, wood, textiles, and plastics. The primary chemical used to fight these fires is monoammonium phosphate, because of its ability to smother fires in these types of materials.


Fire extinguishers with a Class B rating are effective against flammable liquid fires. These can be fires where cooking liquids, oil, gasoline, kerosene, or paint have become ignited. Two commonly used chemicals are effective in fighting these types of fires. Monoammonium phosphate effectively smothers the fire, while sodium bicarbonate induces a chemical reaction which extinguishes the fire.


Fire extinguishers with a Class C rating are suitable for fires in “live” electrical equipment. Both monoammonium phosphate and sodium bicarbonate are commonly used to fight this type of fire because of their nonconductive properties.

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