Understanding Smoke Alarm Features

smoke alarm testing

U.S. Fire Administration

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.

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 interconnected throughout the home (meaning when one alarm sounds, all alarms are activated). You may encounter these in both private and multifamily 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 are connected to it. 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.

 Fire Protection Publications at Oklahoma State University/IFSTA

Fire Protection Publications at Oklahoma State University/IFSTA

Leading national fire organizations and others recommend testing smoke alarm batteries once each month, and replacing batteries at least once per 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 research10 suggests that allowing residents to physically practice these steps leads to better results in maintaining working smoke alarms in high-risk homes. 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.

installing smoke alarmsThere 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 manufacturers’ 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 nationally recognized testing laboratory (NRTL) that is listed by OSHA as accredited to test and certify to Underwriters Laboratories (UL) Standard 217. The following NRTLs are OSHA accredited:

  • Underwriters Laboratories (UL)
  • Factory Mutual (FM)
  • Intertek (ETL)

write date on smoke alarmDuring the visit, look for the manufacturing date 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.