According to codes published by the National Fire Protection Association, you should have smoke alarms inside every bedroom of your house as well as in the hallways outside the bedrooms. There should be one on every level of the house as well as in the kitchen and living area. That's a lot of protection, and if you ever have a fire, you'll be glad you have it. However, smoke alarms do have drawbacks. They can go off for seemingly no reason, and if you use the wrong kind of fire alarm, it could fail to provide warning in sufficient time. Moreover, if you don't replace a smoke alarm after 10 years, it'll start chirping, and that can be really annoying, especially if you don't know how to silence. it. In the worst case, a smoke alarm that's more than 10 years old may not work at all. That would be a terrible thing to discover when a fire actually does occur.
Two Types of Smoke Alarms
The most common smoke alarms – photoelectric ones – employ a light beam to detect smoke particles in the air. When particles are present, they block the beam and the alarm sounds. Less common are ionization smoke alarms, which use a small amount of radioactive material to ionize the air immediately surrounding the sensor. The ionized air creates an electric current between a pair of plates, and when smoke or heat interrupts the current, the alarm sounds.
Photoelectric smoke alarms are better at detecting smoldering fires than open flames, while the reverse is true for ionization alarms. So if you have one but not the other, you aren't getting complete protection. Manufacturers do sell dual alarms. They're the safest and are recommended by the NFPA. However, because disposing of radioactive material is problematic, many people opt for photoelectric ones. That means that their alarms may be slow to respond to a flash fire, which is the most dangerous kind.
The Dreaded Horn
When a smoke alarm sounds, the noise is ear-splitting, so you'd prefer it didn't happen unless it's a real emergency. Unfortunately, smoke alarms often seem to have a mind of their own. What's usually occurring is that steam or smoke from the stove is passing through the sensor chamber. Dust can also collect on the sensor plates and cause a false alarm. Most alarms have a hush button, but that doesn't do much good if the alarm is on the ceiling where you can't reach it. If you're getting frequent false alarms from a unit placed near the bathroom, keep the bathroom door closed after showering until the steam has cleared. If steam or cooking smoke isn't the problem, clean the sensors with a can of compressed air. Still no luck? It's probably time to replace the alarm.
Crickets in the Night
When your smoke alarm starts chirping at one-minute intervals, the batteries are weak and need to be replaced. The chirping sound isn't as disturbing as a false alarm, but it can still keep you awake. You want to sleep, so you go to replace the batteries, but the chirping doesn't stop. That's because you have a model that retains a memory of the weak battery. To clear the memory, disconnect the alarm or turn off the breaker for the smoke alarm circuit, remove the batteries and press the large button on the front of the cover plate. Hold it in for 10 seconds or so until the alarm stops sounding, then put in new batteries and restore the power.
In California, and probably soon in other states, you can no longer buy smoke alarms with replaceable batteries. They're designed to last for 10 years, and if you hear chirping, you have to replace the entire alarm. That may seem like a hassle, but it ensures you always have working smoke alarms to warn you and your family if a fire ever breaks out.