They may not technically be criminals, but smoke and fire are high on the public enemy list. The latest available data from the National Fire Prevention Association (NFPA) shows that fires caused over 3000 deaths, 17500 injuries, and $11.7 million in property damage in 2011. These statistics look even more tragic in the light of other numbers that reveal how easy it is to prevent such tragedies—homes that contain working smoke detectors suffer 90% less property loss and 75% fewer fatalities than homes that don't.
The case for getting a smoke detector is obvious. But what type should you choose? How many should you get? And how should you set them up so that your home is protected, but you don't have to evacuate every time you light a match? We broke down the tech specs and best practices, so you can make popcorn in peace.
Smoke Detector Types
There are three main types of residential smoke detectors — photoelectric, ionization, and combination.
Photoelectric smoke detectors work like this: a beam of light shoots directly above a photoelectric sensor, which detects light. In normal conditions, this beam never touches the sensor. When a high enough concentration of smoke is in the air, the smoke particles interrupt the light beam and act like mirrors, reflecting the light so that it bounces off the sensor, which triggers an alarm.
Ionization smoke detectors work like this: there’s a small chamber with a battery connected to two wires, but these wires are left separated. To get electricity to flow from one wire to the other, the electrical current needs to jump the gap. So this chamber contains a radioisotope, usually americium-241, that charges the air inside. The charged air allows an electric current to flow and jump the gap between the two wires. There’s a little device connected to one of the wires that detects if current is flowing. Normally, current flows through the detector and keeps the alarm quiet. But during a fire, smoke particles enter the chamber and get stuck on the charged air particles. This clogs up the air and stops the electrical current, which sounds the alarm.
Combination smoke detectors—which combine photoelectric and ionization technology—are also available.
Which Should I Choose?
Our opinion: Photoelectric sensors are the best for homeowners. They are safer than ionization, will not drive you crazy with false alarms, and are cheaper than combination alarms, so you can buy as many as you need to fully protect your home.
House fires come in two types: "fast-flaming," which blaze up very quickly, and "smoldering," which develop more slowly. Because they're so sensitive, ionization detectors detect fast-flaming fires slightly faster than photoelectric ones do, by an average of ten to twenty seconds. However, this sensitivity also means ionization detectors are more likely to go off at the slightest cooking mishap. Because homeowners get frustrated at the number of false alarms, they're more likely to disconnect ionization smoke detectors — and a disconnected smoke detector is worse than no smoke detector at all. Meanwhile, photoelectric detectors are much faster than ionization detectors at detecting smoldering fires, by an average of 47 to 53 minutes—a huge difference when it comes to escaping a dangerous situation, especially since many home fires start as smoldering fires.
For these reasons, many experts, including the International Association of Fire Fighters and the Fire Protection Association of Australia, officially recommend photoelectric smoke detectors over ionization smoke detectors, and several states and cities, including Vermont and Massachusetts, legally require photoelectric detectors in residential buildings.
Combination detectors can detect both types of home fires—but just like ionization detectors, they're likely to cause annoying false alarms, which means they're frequently disconnected by aggravated homeowners. Thus, many experts, including the IAFF, do not recommend them. Others agencies recommend combination alarms. But combination alarms are much more expensive, so there is a risk that homeowners will not purchase enough of these sensors to fully protect their homes.
We reviewed all the pros and cons of all the smoke detection technology, and in our view, photoelectric sensors are the safest and most practical choice. We sell a Photoelectric Smoke Detector that is fully integrated into our home security system, so we can call the fire department and have them arrive to rescue your family and your home if disaster strikes.
Like all heroes, smoke detectors are only helpful if they're in the right place at the right time. Here are some installation guidelines from the Consumer Product Safety Commission and the National Fire Prevention Association.
NFPA standards require smoke alarms to be installed outside of sleeping areas, as well as on each floor of your home, including the attic and basement. It's recommended that you place additional sensors in living rooms and dining rooms, but not in bathrooms or directly near kitchen appliances or fireplaces.
- Consider placing smoke detectors all along your planned escape route. Their blinking lights can help you find your way through a smoky hallway to safety.
- To ensure maximum room coverage, smoke detectors should either be placed in the center of the ceiling, or on the wall 6-12 inches below the ceiling.
- Replace your smoke detector batteries at least once a year. Time it with something you do annually anyway, such as setting the clocks back in the fall.
- Test your smoke detector once a week. Do it after dinner on Sunday and sleep easy for the rest of the week!
- Replace entire units after 10 years.
NOTE: All these tips and information apply to residential smoke detectors only, as commercial situations require very different equipment and practices. Homeowners, these tips will get you started — but your local fire marshal should always be your #1 consult.