Recently mom’s smoke detector batteries began their ear-splitting, dying-battery beeping. The local fire department changed the batteries and afterward she asked me the same question she always asks after such episodes: Why do I have to replace batteries in a smoke alarm system that’s hard-wired into my home’s electrical system? Rather than offering my usual shrug, I decided to find the answer. Here it is.

Some smoke detectors rely only on batteries for power. Others are hard-wired into a home’s electrical system and also have a battery to operate the device when the power goes off. Being plugged into the electrical system does not keep the battery charged. It loses its “juice” just like other batteries do over time. That’s why the fire department keeps replacing the batteries in mom’s system.

How can you tell which type is in your loved one’s home? Remove the alarm from the wall. If there are wires coming out of the back, then the system is hard-wired. Note that a hard-wired system may also be tied into the home’s security system.

Check with the fire department in your loved one’s community to find out if replacing smoke detector batteries is a service offered to seniors. If so, remind your loved one to take advantage of the program, especially if he or she cannot or should not be climbing on step stools or ladders (or chairs) anymore.

On a somewhat related note, my research also revealed there are three different types of smoke detectors: ionization, photoelectric, and a combination of the two. Ionization detectors are more responsive to flame, while photoelectric detectors are more responsive to smoke. That’s why fire officials encourage people to install the dual-type. For more information, visit the National Fire Protection Association’s website.