How Do Hard-Wired Smoke Detectors Work?

Smoke detectors are essential for the safety of a home because they detect traces of smoke that result from fire and alert residents by emitting a loud sound. Smoke detectors are battery operated or hardwired. The only difference between the two is that a hardwired detector is connected to a building's power supply. Both still use batteries, and a hardwired smoke detector functions the same as other smoke detectors.

Smoke alarms that are hardwired into the electrical system will work even if you've forgotten to put in a fresh battery -- unless the power goes out.

Power Supply

The battery is an important backup if the power supply of the building fails. A benefit of a connected power supply is that the battery doesn't have to be changed as frequently. A power supply connected to the detector means that the detector has a constant supply of power, essentially never running out.

Photoelectric Smoke Alarm

Some hardwired smoke detectors work with photoelectric sensors that sense smoke through lasers. A laser beams out from the smoke detector and, if it is blocked by smoke, it will raise the alarm, which can be compared to walking into a supermarket where an automatic door opens when a person gets close enough to block the beam. A similar process happens with smoke in photoelectric smoke alarms. These types of detectors, however, do not sound an alert until a lot of smoke is present. More smoke means a bigger fire, so this is not the most beneficial smoke detector.

Ionization Smoke Alarm

Other hardwired smoke detectors are available that use radioactive material, such as americium-241, to detect smoke. Ionization smoke detectors are much more sensitive, detecting significantly smaller amounts of smoke than their photoelectric counterparts and are also much cheaper to produce. Inside the detector, the radioactive material produces alpha particles that ionize the air and carry an electric current. When even trace amounts of smoke enter the detector, it disrupts this electric current and sets off an alarm.

Maintaining Smoke Alarms

Detectors should be maintained properly to ensure that they function well and efficiently. Hardwired detectors need periodic dusting, so taking the cover off and dusting with compressed air is essential. Batteries need replacement about every year even if the detector is hardwired.