Not all fire detectors work the same way: some detect heat while others detect smoke. An ionization fire detector will alert you if there’s a rapid rise in temperature. On the other hand, a photoelectric sensor measures the actual smoke particles in the air, and it will alert you when it detects an abundance of smoke. Therefore, not all fire detectors measure fire safety in the same way.
Recently, Dateline did some practical research regarding the differences in fire detectors. They found that several families with just an ionization fire detector had experienced fires in their home in which the fire alarm never went off. In one extreme case, Amanda Debuty’s home caught fire in the middle of the night and the smoke detectors failed to go off. By the time Debuty woke up she could not get upstairs to her four children, who tragically died in the fire. Debuty told Dateline that she had just tested her fire alarms, and she suspects that she simply had the wrong kind of fire alarm for the type of fire that broke out in her home.
Concerned about the effectiveness of different smoke detectors, Dateline did a controlled experiment at Texas A&M University. Firefighters lit a couch on fire in an enclosed area in two different instances: one with ionization fire detectors and another with photoelectric fire sensors. In the case with the ionization fire detectors, it took 36 minutes for the fire alarms to go off, just before the couch erupted in flames. In contrast, the photoelectric fire detectors went off after just 17 minutes.
With many fires, there is a rapid change in temperature that an ionization fire detector will sense just fine. However, when fires are slow and smoldering there is not necessarily a rapid increase in temperature, and therefore, a photoelectric sensor will work better. In a best case scenario, your home should have both kinds of sensors, or one sensor that incorporates both technologies. Check to see what kind of fire detectors you have in your home, so you know whether your detectors will go off in all scenarios.