Photoelectric smoke alarms are the only smoke alarms you need. Forget dual-sensor smoke alarms, and forget ionization alarms. A recent article in the ASHI Reporter by San Bruno home inspector Skip Walker, titled Silent Alarms; Deadly Differences, convinced me of this.
Last year I wrote a blog post advocating the use of dual-sensor smoke alarms, which incorporate both ionization and photoelectric sensor, but there were enough statistics in this recent article to convince me they're not that great. If you already have dual-sensor smoke alarms, don't throw them out... but don't bother buying them next time. Just buy photoelectric smoke alarms.
Here are the main points advocating the use of photoelectric smoke alarms over dual-sensor smoke alarms.
- The perceived benefit of a dual-sensor smoke alarm is an increased response time to a fast flaming fire.
- Ionization alarms are prone to nuisance tripping. When smoke alarms experience nuisance tripping, they are often disabled.
- In approximately 1/3 of all U.S. fire deaths, the smoke alarm has been disabled.
- There is no industry standard for sensitivity levels in dual-sensor smoke alarms; as long as the alarm sounds within the UL 217 requirements for single sensor alarms, the smoke alarm passes.
- Dual-sensor smoke alarms can have the sensors adjusted to different sensitivity levels for the ionization and photoelectric sensors, provided one of the sensors goes off in a timely manner. This means that a dual-sensor alarm could theoretically have a non-functional ionization sensor, but as long as the photoelectric sensor makes the alarm sound, it meets UL 217 requirements.
- When the ionization sensor is adjusted to go off quickly, the potential for nuisance alarms will go up, which increases the potential for the smoke alarm to be disabled.
- When the ionization sensor is adjusted to take longer to go off, the perceived benefit of a faster response time to a fast flaming fire is diminished.
The International Association of Fire Fighters (IAFF) advocates the use of photoelectric smoke alarms, and in January of 2013, the American Society of Home Inspectors (ASHI) became the first home inspection organization to advocate the use of photoelectric smoke alarms. As an ASHI Certified Inspector, I'll be doing the same. If you're curious about what type of smoke alarms you have in your own home, click here for info on how to determine what type of smoke alarm you have. The bottom line is that every home should be equipped with photoelectric smoke alarms.
For more info on this topic, check out the videos below.
Rossen Reports: A news clip showing the difference between ionization and photoelectric smoke alarms, and a stammering representative from CPSC with no plausible excuse for the many known failures of ionization smoke alarms.
ASHI Vice-President Bill Loden conducts a test showing the differences between ionization and photoelectric smoke alarms.
Author: Reuben Saltzman, Structure Tech Home Inspections