The kind of smoke alarm you have in your home may not provide adequate warning during a fire. That’s right, if you have the kind of detection that most U.S. homes have, an ionization-type, you are at risk of dying in your own home without the alarm ever sounding.
This doesn’t seem possible, does it? After all, if there is a fresh battery in your detector and you have tested it to ensure that it is in working order, you and your family members should be safe, right? Maybe not! There is compelling research-based evidence that demonstrates that ionization-type detectors are ineffective in smoldering type fires, the most common cause of fatalities in home fires. In fact, tests have shown that ionization type smoke alarms don’t sound, even after the level of carbon monoxide and smoke reaches deadly concentrations. An alarming amount of documented residential fire deaths have occurred with only the installed ionization type detectors. Had there been a properly installed photoelectric detector in these situations, an alarm would have sounded to warn occupants of the life-threatening situation.
A 1994 study at Texas A&M concluded that the probability of a photoelectric detector failing to detect a smoldering fire is 4%, while the ionization detector provided close to 56% probability of failure in the same fire condition.
One of the reasons for the differences in the performance of these two detector types is in the way they are activated. Ionization smoke alarms contain a small amount of radioactive material and establish a small electric current between two metal plates. When the current is disrupted by smoke, the alarm sounds. This older type of technology is typically more responsive to a flaming fire, such as a kitchen pan fire, but it’s also more susceptible to nuisance alarms from bathroom humidity or cooking vapors when placed within 20 feet of a kitchen.
Photoelectric smoke alarms contain a light source and a light-sensitive electric cell. Smoke entering the detector deflects light onto the light-sensitive electric cell, triggering the alarm. These alarms are more sensitive to large particles given off during smoldering fires, such as an electrical fire-the kind of fires that usually occur at night when people are asleep.
For many years, authorities have urged homeowners to install smoke alarms without consideration to the type of potential fire ignition or the quality of smoke detection. This was based on the urgency to equip all homes with smoke detection with what was readily available on the market.
It is no surprise, then, that more than 90% of homes in the United States have only the ionization detection technology, leaving those occupants vulnerable to the most common and deadly type of fire.