6 Types of Smoke Detectors for Your Home
Updated: May 02, 2024
Working smoke detectors save lives. Here's what you need to know about these important safety devices.
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Look around your home. Do you see multiple smoke alarms? At a minimum, you should have one on every level of your house, one in every bedroom and one near all sleeping areas (even if that’s not a bedroom).
Working smoke detectors (alarms) make the difference between life and death in a home fire.
“Today’s home fires burn faster than ever,” according to Susan McKelvey, communications manager for the National Fire Protection Association (NFPA). “In a typical home fire, you may have as little as two minutes to escape safely from the time a smoke alarm sounds.”
In the event of a fire, homes with working smoke alarms suffer fewer than than half the deaths as those without them, according to the NFPA.
A note about terminology: You may hear, or use, “smoke detector” and “smoke alarm” interchangeably. Technically, smoke detectors only detect smoke, then send a signal to a building’s fire alarm system. The standalone units we have in our homes are smoke alarms, which detect smoke and sound an alarm, all in one device.
McKelvey identifies two types of smoke alarms: ionization and photoelectric. They work on different types of fires, so the NFPA recommends buying alarms that combine these two technologies. First, I’ll explain how smoke alarms work, then take you through the different ways you can employ these life-saving devices.
Ionization
Ionization smoke alarms use a battery and two metal plates, called electrodes, to create an electrical circuit. Ions are tiny, electrically charged particles that flow through the circuit and between the two plates. When smoke enters the detector, it disrupts the flow of current and activates the alarm.
Ionization smoke alarms work best on fires with active flames, also called “flaming fires,” McKelvey says. These can be from flammable liquids, paper or wood, and may have less smoke than flames. Many house fires are considered fast-flaming fires.
Photoelectric
Photoelectric smoke alarms work best on smoldering fires, or fires that take a long time to get going.
Instead of an electric circuit, photoelectric smoke alarms use a beam of light and a sensor to detect smoke particles. The light beam stays fixed, pointed across the inside of a chamber inside the device. When smoke particles disrupt the light beam, the sensor sets off the alarm.
Smoldering fires can be caused by unattended cigarettes and other slow-burning ignition sources, resulting in heavy clouds of smoke compared to flames. Smoldering fires can turn into flaming fires as they ignite other materials in the home.
Combination
“Both types of alarms are designed to alert people to fire in time to get out safely,” McKelvey says. But because house fires can be flaming or smoldering, and you can’t know beforehand what type of fire may start, the NFPA recommends buying combination smoke alarms. These employ both technologies — ionization and photoelectric — in one device.
All three types of smoke alarms come in battery, hard-wired and smart versions. Each offers different advantages.
Battery-Operated
Battery-operated smoke alarms are relatively inexpensive, and they don’t take any special knowledge to install. You can pick up a two-pack of ionization smoke alarms for less than $15, available at any home improvement center. Photoelectric smoke alarms are a little more expensive due to their more complicated technology; a two-pack will cost you about $40.
Traditionally, battery-operated smoke alarms used nine-volt batteries, but increasingly these are changing to AA or even lithium-ion. If the batteries are replaceable, the alarm will chirp when they’re running low. Regardless of battery life, always replace smoke alarms every 10 years.
Hard-Wired
These use the same technology as those with batteries, but they’re powered by a circuit fed from your electrical panel. That means as long as you have electricity, you don’t have to worry about dead batteries. If you do lose power, hard-wired smoke alarms have a backup battery that will beep if it ever needs replacing.
Hard-wired smoke detectors are more difficult to install in existing homes, because each needs to be connected to each other and the electrical circuit, using a wiring system like Romex. They do have an advantage over traditional battery-operated alarms because if one goes off, they all go off, which will alert your entire home of danger.
Smart/Wireless
If you love telling Alexa or Siri to turn on your lights or turn down the air conditioning, you’re in luck. Smart smoke detectors also exist, and like hard-wired ones, they’re interconnected to alert your entire home. Some systems, like Google Nest Protect, can send alerts to your phone and connect to an external monitoring system.
You don’t have to spend a fortune to get smart protection, though. “There are smart alarms on the market that detect smoke, carbon monoxide (CO) and other issues in one system,” McKelvey says. “But they offer no advantage in detecting or alerting people to fire over other hard-wired or wireless smoke alarm systems.”
Simple wireless smoke detectors, like First Alert’s wireless smoke alarm, use wireless tech to interconnect. They’re easy to install and provide great protection at a reasonable price.
The Most Important Thing
No matter what kind of smoke alarms you buy, McKelvey says, make sure they work! Check to see they bear the mark of an independent testing laboratory, like UL or Intertek, to ensure they’ve been tested to established safety standards.
Test smoke alarms monthly, and replace them every 10 years to ensure maximum effectiveness. (Reduce that to every seven years for CO/fire combination detectors.) If you’re not sure when your smoke alarm was installed, check the manufacture date listed on the device.
“In the end, having the proper number of working smoke alarms installed [regardless of the type] in the correct locations is key when it comes to safety,” McKelvey says.
Originally Published: September 18, 2023
