Why would a fire extinguisher class icon have a red slash through it?

A. Because using the extinguisher on that class of fire would be ineffective

B. Because using the extinguisher on that class of fire would create additional risk

C. Because the use of that type of extinguisher on that class has not been tested

D. Because it is illegal to use that type of extinguisher on that class of fire for environmental reasons

A fire extinguisher icon with a red slash indicates it's not safe to use on that class of fire, either due to ineffectiveness or the potential for additional hazards, such as spreading the fire or causing electrocution, especially with electric fires where water can conduct electricity.

Explanation:

A fire extinguisher class icon may have a red slash through it to indicate that using the extinguisher on that class of fire would be either ineffective or could create additional risk. Especially in cases of electric fires, introducing water can cause the fire to spread due to water's conductivity, or it can create an electrocution hazard. Therefore, it's vital to use the correct type of extinguisher for the specific class of fire you are confronting.

We are advised not to flick electric switches with wet hands because water is a good conductor of electricity, and you could get an electric shock. Similarly, throwing water on an electric fire is dangerous because it can cause electrical currents to travel unpredictably, potentially leading to electrocution or spreading the fire.