Home Inspectors Guide: Smoke Detectors

Smoke  detectors, those things you never think about until you burn dinner or the low battery chirp wakes you up at three a.m. Here are a few facts about the little device that could save your life. While conducting home inspections in Baltimore I often find them missing, outdated or non-functional.

What are the different types of smoke detector?

There are two basic types: ionization and photoelectric. Ionization uses a tiny amount of a radioactive element to pass an electrical current through the air between two metal plates. When that flow is interrupted, the alarm sounds. Photoelectric detectors use light to detect smoke particles.  Ionization detectors are better at detecting flaming fires, while photoelectric detectors are better at detecting smoldering fires. There are also combination detectors that use both technologies. Photoelectric are often preferred near kitchens and baths as they are less likely to be tripped by steam from cooking or bathing. It’s a good idea to have both technologies in your home.

Battery smoke detectors vs. Hardwired smoke detectors:

Many new construction homes and rehabs have hardwired smoke detectors that use the homes AC power supply. Modern detectors have a battery backup, though some older units may not. Those units are probably due for replacement. Wired smoke detectors can also be connected so that every alarm will sound if anyone is tripped.  Battery units are a good choice if the home isn’t equipped for hardwired detectors. Today, the standard is a ten-year sealed battery. Since smoke detectors should be replaced every 10 years, this makes maintenance simple.  Whatever type you use, they should be tested on a monthly basis. If you still have removable battery alarms, the batteries should be changed twice a year, including backup batteries for hardwired detectors.  Check the back of your smoke detectors for a manufacture date to find out how old they are.

Smoke Detectors Manufacture Date
Smoke Detector Manufacture Date

How many smoke detectors do I need?

Smoke detectors should be installed at least one per floor, one outside each sleeping area, and one in each bedroom. Obviously, those requirements overlap. So, in a house with three bedrooms on the second floor, that floor would require 4 detectors, one in each room, with the fourth in the hallway meeting the first two requirements. Of course, you should check your local code for requirements in your area. As a home inspector, I’m happy to help you find out how many you need.

Do I need Carbon Monoxide (CO) detectors?

Carbon monoxide is a colorless, odorless gas that is produced as a byproduct of combustion.  If your home has any gas, oil or wood burning appliances, you need carbon monoxide detectors. Conveniently, many manufacturers offer combination smoke/CO detectors. I also check for CO detectors during my home inspections.

For more information visit the National Fire Prevention Association.