What is the main danger of using a Class A extinguisher on a Class B fire?

Using a Class A extinguisher on a Class B fire can indeed cause the fire to spread instead of extinguishing it. Class A extinguishers are designed for fires fueled by ordinary combustibles like wood, paper, and textiles. In contrast, Class B fires involve flammable liquids such as gasoline, oils, and solvents.

When a Class A extinguisher is applied to a Class B fire, especially if the extinguisher uses water as its primary extinguishing agent, it can have a dangerous effect. Water may cause the flammable liquid to float or disperse, leading to a wider spread of the fire. This can result in an increased risk of the fire becoming more uncontrollable instead of being effectively put out.

Other potential responses that touch on risks associated with using inappropriate extinguishers do not convey the primary danger as clearly. For example, concerns about an explosion or the efficacy of the extinguishing might arise, but the key issue remains that the inappropriate use of the extinguisher type could enhance, rather than mitigate, the fire risk.