Which of the following is NOT a property of a pressurized water extinguisher?

The correct answer is that a pressurized water extinguisher is not designed specifically for Class B fires. Pressurized water extinguishers are primarily intended for use on Class A fires, which involve ordinary combustibles such as wood, paper, and cloth. They work by cooling the burning material and reducing its temperature below the ignition point.

While these extinguishers can technically be used on certain types of Class B fires (which involve flammable liquids), doing so may be problematic because water can spread these kinds of fires rather than extinguish them effectively. Therefore, it is critical to use extinguishers that are specifically rated for Class B fires, like foam or dry chemical extinguishers, which are designed to handle flammable liquids effectively.

The other properties mentioned about a pressurized water extinguisher highlight its operational flexibility (can be started and stopped as necessary) and its effectiveness in cooling burning materials (extinguishes by cooling). These aspects are integral to how the extinguisher functions to suppress fires on appropriate materials.