Ionization or photoelectric: Which does what, and is ‘better’?
After an emotional news report about the weaknesses of the most common type of smoke detector, Ridgefield Fire Chief Heather Burford and international fire chiefs say the devices are still life savers.
Chief Burford agrees it’s surprising to most people that there is more than one type of smoke detector, in part because firefighters emphasize what she says is the most important message, and one she doesn’t want to over-complicate: Get smoke detectors. Any detector is better than none.
“When you reach for a smoke detector you believe that it’s a smoke detector,” Chief Burford said.
As the report, which aired on the NBC’s Today Show and the NBC Nightly News with Brian Williams last week, points out, there are two different smoke-sensing technologies in smoke detectors: Ionization and photoelectric.
Ionization detectors are the most common type of detector, they cost less, and, in a test that was part of the news segment, they didn’t perform as well as the photoelectric sensors. In a smoldering, smoky fire without big flames, the ionization detector took 36 minutes to sound compared with the photoelectric detector’s 17 minutes.
Accompanying the study, the news segment featured a mother who lost three of her children in a fire in her home that reportedly had working ionization detectors.
Chief Burford acknowledged there are differences between the technologies, since they both have strengths and weaknesses.
According to the box of an off-the-shelf ionization smoke detector, photoelectric sensors are better at detecting larger smoke particles produced in smoldering fires, while ionization sensors are better at detecting small particles caused by big flames.
Chief Burford said a cigarette in a couch cushion would typically create smoldering smoke, while a grease fire in the kitchen would cause more flaming fires.
The box also says “For maximum protection: Use both types of smoke alarms in every bedroom and on every level of your home.”
That’s a recommendation the International Association of Fire Chiefs agrees with.
Additionally Chief Burford said, people should have carbon monoxide detectors, too.
The photoelectric detectors are harder to find, and cost more. There are also combination detectors that have both types of sensors.
“Going forward we will offer both types,” Chief Burford said.
In the past she has estimated some 50% of Ridgefield homes don’t have smoke detectors or don’t have them properly placed and installed. Shrinking that number has been a priority of the department and a public outreach challenge. While any complex with three or more housing units can be checked by the building department for proper carbon monoxide and smoke detectors, the town has no jurisdiction over one and two-family homes, except when it comes to granting the certificate of occupancy.
Smoke detector tips
Lots of homes have carbon monoxide (CO) and smoke detectors that are not maintained properly.
Here are the basics:
- They should be tested every month — push the button and wait for the beep.
- The batteries should be replaced twice per year. The fire department recommends doing it when you change your clocks in the spring and fall.
- The detectors themselves do wear out — they have to be changed at least every 10 years. Check the manufacturer’s recommendations.
- Smoke detectors should be placed on all levels and in every sleeping room (that includes an office with a fold-out couch); in hallways more than 20 feet long outside of sleeping rooms.
- CO detectors should be near all sleeping rooms.
