Charlie Glahe WIN Broomfield

Understanding the difference between ionization, photoelectric smoke detectors


With a home purchase being one of the most significant financial decisions a person will make in their lifetime, it's natural to want to protect that residence from any potential danger that can result. While achieving this ideal can be difficult, particularly for those who reside in areas where drastic weather events occur with some regularity, homeowners can at the very least reduce the risk of property damage by ensuring that their home has working smoke detectors.

But for many years, there has been a considerable amount of debate about the type of smoke detector that works best - ionization or photoelectric. According to experts on the topic, it's hard to determine which one is best because they both have their own unique set of strengths.

Ionization models are the ones that most homeowners have. Though how they work is somewhat complex, they basically function by utilizing a small amount of radioactive material that's within the chamber. When flame is detected, the electrodes - which are also within the detector - detect airflow that diminishes when some type of combustion has been distinguished. It's this reduced conductivity that causes the alarm to sound.

A photoelectric smoke alarm - as the name suggests - uses visual cues to detect fire. So when smoke or flame is in the area of the alarm, a light emitting diode scatters light that is detected by sensors within the chamber, signaling the detector to make a sound.

Ionization, photoelectric react based on intensity of fire
Just as the way in which the alarms operate differ, they also react in a dissimilar fashion, depending on the type of fire that's present. Photoelectric alarms, experts say, are best for fires that produce a small amount of heat, such as those where there's smoldering action. In other words, when a conflagration takes a while, photoelectric alarms work best. Ionization type alarms react more effectively for fires that produce intense heat. For example, grease fires or any other highly combustible material - such as newspaper - is where ionization alarms work best.

It's important to note that both alarms should sound off when any conditions associated with flame are present. However, how quickly one reacts versus the other depends on the flame and the detector. In addition, according to the National Fire Protection Association, either type of smoke alarm should give homeowners and families with plenty of advanced warning so that they can escape their house if a fire is present.

While studies into which type is the most effective are on going, fire officials agree that for the most part, one is not necessarily better than the other because they both respond to fire but in accordance with the conditions that are most suitable to its functionality. It's for this reason that homeowners should use both types of smoke detectors in their homes by placing them in rooms based on the potential for a specific type of fire. For example, because they're more reactive to smoke, photoelectric are best in the kitchen, where there may be smoldering. But for ionization alarms, which react best to fires that produce high heat quickly, these are most suitable for areas of the home where a fire could ignite quickly. In other words, in any place where there are highly combustible materials.

Bill Loden, vice president of the American Society of Home Inspectors, was recently interviewed by a Huntsville, Alabama local news affiliate, describing how smoke alarms factor into the home inspection process.

"Ninety-five percent of homes in this country have ionization alarms," Loden told WHNT News.

He added that insuring that these smoke alarms are fully operational is often a matter of life and death, as thousands of people have died unnecessarily due to detectors not working or falling into disrepair.