- Smoke alarms detect smoke and sound an alert, while smoke detectors typically sense smoke and connect to a building fire alarm system.
- Common smoke alarm types include ionization, photoelectric, dual-sensor, multi-criteria, voice, and combination smoke/CO alarms, each designed for different fire detection needs.
- Smoke alarms can be powered by replaceable batteries, sealed 10-year batteries, or hardwired connections with battery backup.
- For effective protection, smoke alarms should be installed in bedrooms, sleeping areas, on every level of the home, and in suitable locations away from excessive airflow, cooking smoke, and shower steam.
- Regular testing, timely replacement, proper interconnection, and recognized third-party certification are essential for maintaining reliable smoke alarm performance.
Smoke alarms are crucial for fire safety in your home, as homes with smoke alarms installed have a 55% lower risk of death in structural house fires compared to homes without alarms or alarms that don’t work. Buying a smoke alarm can be a bit confusing for people who are not familiar with all the different types and terminology in use. Therefore, I will break down some of the most common questions to help you choose the best alarm.
I want to point out that smoke “detectors” and smoke “alarms” are different. Essentially, a smoke detector is just a sensor that monitors smoke and is connected to the building’s fire alarm system, while a smoke alarm has both a smoke sensor and a speaker that sounds an alarm to alert occupants.
What are the different types of smoke alarms?
Properly installing the appropriate number of working smoke alarms, regardless of type, in the right locations is key to safety.
Ionization vs. Photoelectric
There are several different types of alarms that you can purchase, each with their own pros and cons. The first difference you’ll see is between ionization and photoelectric alarms. The difference between the two is the type of sensor used to detect smoke. Ionization smoke alarms are typically more sensitive to flames (imagine a fire that you can see) while photoelectric smoke alarms are typically more sensitive to smoldering fires (like a cigarette).
Ionization
Ionization smoke alarms use a small amount of radioactive material to ionize air molecules into positively and negatively charged molecules, which creates a small electrical current. When smoke enters the ionized air, it reduces the current, causing the smoke alarm to sound. Generally, smoke alarms with ionization detectors tend to be less expensive than those with photoelectric detectors.
（Image from： NPFA）
Photoelectric
Photoelectric smoke alarms use a light source and a photosensitive cell. When smoke enters the chamber, the light is scattered and picked up by the photosensitive cell, causing the alarm to sound.
（Image from： NPFA）
Combination Ionization and Photoelectric
For the best protection against smoldering fires and flaming fires, you can get an alarm with dual sensors. These alarms have both an ionization sensor and a photoelectric sensor, which will cause the alarm to sound. Dual-sensor alarms offer the best protection and are recommended.
Smart Multi-Criteria Alarms
Smart Multi-criteria alarms use different sensors, such as photoelectric,heat and ionization, and algorithms to detect fires. Because of the multiple sensors, this type of alarm is better at reducing unnecessary nuisance alarms from non-fire scenarios, such as when you’re cooking and the alarm detects light and heat instead of a fire .
Voice Smoke Alarms
Some smoke alarms have 3 patterns (a series of three loud beeps) with different voice notifications that can tell you where smoke is detected or if the smoke alarm is wrong.
What is a combination carbon monoxide (CO) and smoke alarm?
Combination carbon monoxide and smoke alarms are devices that detect both smoke and carbon monoxide. Carbon monoxide is a colorless, odorless, poisonous gas that can cause serious health problems and even death if it accumulates in an enclosed space. This type of alarm is a good choice if you want to install one device with both detectors fuctions.
Our Standalone smoke detector SD-436
How do smoke detectors get power?
Smoke detectors can obtain electrical power in various ways.
Replaceable Batteries
Some smoke detectors rely entirely on replaceable batteries, which can be 9V batteries, AAA batteries, AA batteries, or other types of batteries. These batteries should be replaced at least once a year, and the alarm should be tested monthly.
10-Year Battery Alarms
Some smoke detectors come with sealed, non-replaceable batteries that can provide power for up to 10 years. These alarms do not require battery replacement, but you should still test them monthly.
Hardwired with Backup Battery
Some smoke detectors are hardwired into the home’s electrical system for their primary power source and have a backup battery as a secondary power source. The backup battery can be either a replaceable battery that needs to be replaced at least once a year or a sealed battery that can last up to 10 years without replacement.
Do I Need Battery or Wired Smoke Detectors?
If your home has hardwiring, you should replace the smoke detector with a hardwired smoke alarm from the same manufacturer. You can use a different manufacturer, but it may require an electrician to come in and wire in different plugs (see also the interconnect section below).
If you are doing renovations or building a new home, consult with the local building department and/or fire department for code requirements.
How Often Should I Replace My Smoke Detectors?
Smoke detectors must be replaced:
every 10 years according to the manufacturer date on the back label (combination carbon monoxide/smoke alarms are 7 years)
if the alarm sounds the end of life signal (see signal description on the back of the alarm)
if the alarm does not pass the monthly operational test
or after a fire
How Do I Know if I am Purchasing a Quality Smoke Alarm?
Smoke alarms need to be tested by a third-party accredited laboratory to strict product standards. Make sure the alarm you purchase has been tested by a recognized testing laboratory and has a label (shown on the packaging and the alarm label).
What are Interconnected Smoke Alarms and Do I Need Them?
Interconnected smoke alarms refer to the linking of alarms so that if one alarm sounds, all the alarms in the house will sound. Interconnected smoke alarms are more likely to alert occupants in a building of a fire anywhere in the building. Therefore, new building, fire, and life safety codes will require smoke alarms in new or remodeled construction to be interconnected.
Typically, if you are just replacing one alarm, you can replace it with the same type that is already there. If they are currently interconnected, then you need to replace them with interconnected alarms. If they are not interconnected, it is not necessary to install interconnected alarms, but interconnected alarms will provide an additional level of safety. Interconnected Smoke Alarms will make you safer and more secure when you are at home.
You can get smoke alarms that are interconnected by wired or wireless connections. If your smoke alarm is hardwired, check to see if there are three wires coming out of the alarm. If they are all connected, it is likely that the alarms are interconnected. If the smoke alarm is not hardwired, then you need to check if the alarm can be wirelessly interconnected. You can also simply press the test button on one alarm and listen for the other alarms in the house to sound.
Where should I install smoke alarms in my home?
Check your local building, fire, or life safety codes for specific requirements in your area, or contact your local fire department. However, smoke alarms are generally required to be installed:
Inside each bedroom, outside each sleeping area (such as hallways), and on every level of the home, including the basement.
On floors without bedrooms, alarms should be installed in the living room (or den or family room) or near the stairway to the upper level, or both.
Smoke alarms installed in the basement should be placed on the ceiling at the bottom of the stairs leading to the next level.
Larger homes may require additional smoke alarms.
Should I mount my smoke alarm on the ceiling or on the wall?
Smoke alarms can be mounted high on the wall or on the ceiling, both installation is okay as the smoke will rise.
Wall-mounted alarms should be installed no more than 12 inches (300 mm) from the ceiling (measured to the top of the alarm). However, if your ceiling is sloped, install the alarm within 36 inches (910 mm) of the peak, but not within the peak (four inches (100 mm) down from the peak).
Avoid mounting smoke alarms near areas with airflow or drafts, such as near windows or vents from HVAC systems.
How can I reduce false alarms?
If you need to place smoke alarms near cooking appliances or bathroom doors due to the layout of your home, keep in mind some things to reduce false alarms.
To limit the number of false alarms caused by cooking, you should place alarms at least 20 feet (6.1 m) away from cooking appliances. If the alarm is photoelectric, has a hush button, or is listed as being resistant to common cooking smoke, you can place it as close as 10 feet (3.0 m) from cooking appliances.
If placing smoke alarms in hallways near bathrooms with showers, they should be placed at least 36 inches (910 mm) away from the door to reduce the impact of steam from the shower on the alarm.
What if someone in my home is deaf or hard of hearing?
There are smoke alarms and alert devices available to alert people who are deaf or hard of hearing. These devices include strobe lights that flash when the smoke alarm sounds to alert people. You can also purchase and install pillows or bed shakers designed specifically for your smoke alarm.
To limit the number of false alarms caused by cooking, you should place alarms at least 20 feet (6.1 m) away from cooking appliances. If the alarm is photoelectric, has a hush button, or is listed as being resistant to common cooking smoke, you can place it as close as 10 feet (3.0 m) from cooking appliances.
If placing smoke alarms in hallways near bathrooms with showers, they should be placed at least 36 inches (910 mm) away from the door to reduce the impact of steam from the shower on the alarm.