What type of fires is a B:C extinguisher not effective against?

A B:C extinguisher is designed to be effective against flammable liquid fires (Class B) and electrical fires (Class C). It uses a dry chemical agent, typically sodium bicarbonate or potassium bicarbonate, to extinguish fires by disrupting the chemical reaction taking place in the fire.

Fires involving combustible metals, such as magnesium, sodium, and lithium, fall under Class D fires. These types of fires require specialized extinguishing agents that can react appropriately with metals, preventing further combustion. Therefore, the B:C extinguisher is not suitable for tackling fires involving combustible metals, as the dry chemical agent can react improperly with these materials, potentially exacerbating the fire instead of extinguishing it.

In contrast, B:C extinguishers work well on electrical equipment and flammable liquids, which is why those types of fires are included in their effective range. Cooking oil fires would typically require a Class K extinguisher in kitchens, so they are also not suitable for B:C extinguishers. Fires from plastic materials may fall under Class A depending on their composition, but these are also better dealt with using other types of extinguishers. Thus, the clarity around what a B:C extinguisher can effectively combat highlights its limitations regarding combustible metal