What Does Class B Fire Mean?
Class B fire refers to a fire involving flammable liquids such as petroleum (gasoline, kerosene, petrol, diesel, octane, etc.), paint, alcohol, solvent, oil and tar, etc. that normally do not leave any embers or residues (or very low amounts of residues). Most of these liquids have a high carbon content and the compounds in them and are highly combustible.
Safeopedia Explains Class B Fire
A class B fire does not leave embers or ashes and can be best extinguished by providing a wall between the fuel and the oxygen, a technique known as smothering. The most effective extinguishing agent against a class B fire is foam. However, the type of foam to be used depends on whether it is water soluble or hydrocarbon.
A small class B fire can also be extinguished by multipurpose dry chemical powder or by water mist that can effectively cool the fire. Re-ignition may also occur if the sources of heating the substance (above the ignition temperature) are not removed. One should never use water stream on a class B fire as it helps to spread the fire since these liquids are lighter than the water.