For which types of fires is the photoelectric type of alarm less effective?

The photoelectric type of smoke alarm is generally less effective for fires involving flammable liquids such as gasoline and alcohol. These types of fires can produce more rapid flames and less smoke compared to solid material fires, which often create large amounts of particulate matter that a photoelectric detector is designed to sense.

Photoelectric alarms work best in environments where the smoke particles from smoldering materials, like wood and paper, are more prevalent. In contrast, flammable liquid fires can ignite quickly and burn intensely, producing different smoke characteristics that might not activate the photoelectric sensor as effectively. Therefore, while photoelectric alarms are an excellent choice for detecting the early stages of various types of fires, they have limitations when it comes to liquid fires where the ignition and flame dynamics differ significantly from those of solid materials.