On Palm Sunday, 2003, there was an overnight fire at an off campus house near Ohio State University. 5 students died. 2 years later, also on Palm Sunday, there was another off campus fire. This time at Miami of Ohio University. 3 students died. Between the 2 houses there were more than 20 ionization smoke alarms present, yet 8 students died. More on ionization smoke alarms later.
On November 18, 2014, the Consumer Products Safety Commission (CPSC) for the first time publicly acknowledged that current smoke alarms have only a 45-49% overall alarm success rate and supported significant changes to the UL 217 alarm testing standards. This is a very poor rate of performance, especially for something as important as a warning to get out of a burning building! So what is the problem? It turns out that there are two kinds of smoke alarms: Ionization and Photoelectric. Most people have ionization alarms- in fact, they are present in over 90% of homes. We are now finding out that ionization alarms have big weaknesses. Ionization alarms are not as good at detecting smoldering fires. This means that with these alarms, there is often a delay in sounding the alarm. This delay can make all the difference between surviving a fire or succumbing to it. The National Institute of Standards and Technology has tested smoke alarms and has reportedly determined that ionization alarms are 30 minutes slower, on average, to sound an alarm in the early smoldering stage of fires than photoelectric alarms, and may completely fail to sound at all! A smoldering fire can produce a lot of deadly fumes in 30 minutes. Ionization alarms are also more likely to sound a false alarm from a bit of smoke produced by cooking in the kitchen, or the mist from a hot shower. False alarms are a big problem because a lot of people end up disconnecting their alarms because of these. And a disconnected smoke alarm has a 0% chance of warning you of a fire. Photoelectric smoke alarms on the other hand, will almost always give a much earlier warning in the case of smoldering fires. Since many fires start out by smoldering for a period of time, an earlier warning of these types of fires can buy you precious time to get out of a burning building. As for the issue of false alarms, photoelectric alarms are much less likely to produce these than ionization alarms. So which kind should you buy? I believe that photoelectric alarms are the better choice hands down. The International Association of Fire Fighters and ASHI, the American Society of Home Inspectors are now recommending photoelectric smoke alarms over ionization.
Another option is to buy combination smoke alarms. These types have, both photoelectric and ionization detectors built into them. Underwriters Laboratories (UL) recommends this approach. However some of these alarms will not sound unless both detectors in them recognize the need to sound the alarm. This makes it even less likely that it will sound in a timely manner. And there is still the problem of nuisance or false alarms. Still other alarm types combine a smoke alarm with a carbon monoxide alarm. Some of the new alarms can even talk. Can you imagine your alarm yelling "Fire! Fire!", or "Carbon Monoxide!". Another nice feature: Some newer smoke alarms have a long life lithium battery. It is good for the 10 year life of the alarm. And after 10 years of so, when it's time to replace the smoke alarm, it will tell you! Just think- No more replacing batteries! That has always been such a hassle.
If you're in the market for smoke alarms, or want to replace your old ionization alarms with a safer alternative, choose photoelectric. --- Kim Christensen