There are many different brands of smoke alarms available, but most fall under two basic types: ionization and photoelectric. Some alarms are dual sensor and have one of each in the same unit. In addition to these, there are alarms and alert devices available for people with hearing disabilities, and alarms that also detect the presence of carbon monoxide. Understanding how these alarms work, and the proper installation and maintenance of these alarms is critical for educating the residents during your home safety visits.
Understanding Smoke Alarm Features
Ionization or photoelectric alarms can be battery operated or hard-wired. Battery powered units run on 9-volt or AA batteries, or a long-life lithium battery that may be sealed inside the alarm so the battery is non-replaceable. This feature is referred to as tamper-proof.
Hard-wired units are wired directly into the home’s electrical system. Some will also have a backup battery that will power the alarm in case of a power outage. Hard-wired units are often inter-connected throughout the home (meaning when one alarm sounds, all alarms are activated). You may encounter these in both private and multi-family homes.
This guide does not address installation of hard-wired smoke alarms, since most fire departments install only battery-powered alarms. They are faster to install and do not require an electrician. If you do encounter a hard-wired smoke alarm, still test it to see if it is operational and if it activates the other smoke alarms that it is connected with. Also, check the date on it to see if it is more than 10 years old and if the battery is still operational. If the system is connected to an alarm company, notify the monitoring service before you test the alarm.
USFA and others recommend testing smoke alarm batteries once each month, and replacing batteries at least once a year or when the alarm “chirps,” signaling the power in the unit is low. It is very important while conducting the home safety visit that you demonstrate to the residents how to test their alarms monthly and how to change the batteries and/or replace long-life alarms and alarms with sealed batteries.
When applicable, show how the hush button feature works. Don’t assume that people know about this feature. New research* suggests that allowing residents to physically practice these steps leads to better results in maintaining working smoke alarms in high-risk homes.
(*SOURCE: Increasing smoke alarm operability through theory-based health education: a randomised trial
Miller TR, et al. J Epidemiol Community Health 2014;0:1–7. doi:10.1136/jech-2014-204182) It is important to leave the instructions that are packaged with the smoke alarm and alert equipment with the consumer. But since some residents may not be able to read and understand them easily, take the time to talk through the key steps to maintaining working smoke alarms.
There are distinct differences between ionization and photoelectric alarms. Either smoke sensing technology provides adequate warning of home fires. Ionization is more effective in detecting flaming fires. Photoelectric is more effective in detecting smoldering fires that make dark smoke. For best protection, it is recommend that every home have some of both Ionization and photoelectric smoke alarms. In homes where recommended installation distance from kitchens and bathrooms is an issue, use photoelectric models to reduce nuisance alarms (because ionization alarms are more likely to signal from cooking vapors and steam near these areas). Read the manufacturer’s instructions for more details about proper location of smoke alarms.
It is important to inform the residents that all smoke alarms have a life of no more than 10 years. All alarms older than 10 years must be replaced.
When purchasing and installing smoke alarms, be sure to check the package to ensure they are listed by a national testing laboratory (NRTL) that is listed by OSHA as accredited to test and certify to Underwriters Laboratories (UL) Standard 217 . The following NRTL’s are OSHA accredited:
- Underwriters Laboratories (UL)
- Factory Mutual (FM)
- Intertek (ETL)
During the visit, look for the date of manufacture on the back of the alarms already present in the home. If you do not see one, replace the alarm and write the date of installation on the inside cover.
Smoke Alarms for People with Hearing Loss—People who are hard of hearing need an alert device installed where they sleep that makes a low frequency sound and activates a bed shaker for a tactile alert. People who are deaf need the bed shaker to wake them up and a visual alert such as a strobe light. For more information:
Home Fire Safety Solutions Smoke Alarm Project, developed by Oklahoma State University’s Fire Protection Publications and Oklahoma Able Tech.
Here are some examples of these specialized alarms and alert devices.
This alert device actively listens for the sound of a conventional smoke alarm. It is not a smoke alarm. It is activated by the signal from a conventional smoke alarm. The Lifetone has 7-day back-up battery power.
When it detects the sound of the smoke alarm, it creates four signals:
- A loud 520 Hz square-wave alarm (90 dB).
- A powerful clam shell-like vibrating bed shaker (placed under the mattress).
- Instruction in a loud voice (“Fire! Get out!”) in multiple languages.
- The word “FIRE” is displayed in large text against a flashing orange backlight.
Installation takes approximately 20 minutes. If you find that it doesn’t respond to the existing smoke alarms, replace them with smoke alarms that generate the correct signal.
This photoelectric, single-station smoke alarm is designed to alert with both an audible and visual signal. The audible alarm is the standard UL 217 temporal three high-frequency sound. The visual alarm is a strobe light. Gentex makes a model that is AC-powered with a 9’ cord and a 9-volt backup battery. The battery provides back up power to the smoke alarm only. The alarm does not require an electrician to install. The alarm is packaged with a small bracket that is used to prevent the alarm from being unplugged. It is secured with the small screw that keeps the receptacle cover in place.
This device is triggered by a conventional smoke alarm sound and includes a motorized bed shaker, a flashing light, and a low frequency, high-decibel square wave sound.
CAUTION: There are several devices on the market that claim to notify people who are deaf and people who are hard of hearing to a residential smoke alarm sound. At publication time, only two devices are listed by national testing laboratories: Lifetone and SafeAwake, and some Silent Call equipment.