(WHTM) — You might have heard when you change your clocks for Daylight Saving Time, that you should always check your smoke detectors at the same time.

But, while you change out the batteries, did you ever wonder how these devices work and how they save lives?

According to the National Institute of Standards and Technology (NIST), these devices work by detecting particles in the air through one of two types of detection technology: Ionization and photoelectric.

Ionization detectors work by using a small piece of safely shielded radioactive material that electrically charges or ionized the air molecules between two metal places. When air particles enter the chamber, they attract the ions and carry them away, which in turn reduces the current. When the number of particles takes too many of these ions away, the device will register that as smoke, and the alarm will sound.

Photoelectric technology works by detecting light that is reflected off particles from a light beam inside the chamber. When no particles are present in the sensing chamber, the light beam does not hit the light detector, indicating an all-clear. But when there are particles present and the amount of light is registered by the chamber, the alarm sounds.

Both types, of detectors, can trigger by detecting either a slow-burning fire or a flaming fire. The National Fire Protection Association (NFPA) urges homeowners to have both ionization and photoelectric units in their homes. And dual-sensor alarms that combine both technologies are also available. 

The NFPA has the following tips when it comes to smoke detectors in homes:

  • A closed door may slow the spread of smoke, heat, and fire. Install smoke alarms in every sleeping room and outside each separate sleeping area. Install alarms on every level of the home. Install alarms in the basement. Smoke alarms should be interconnected. When one sounds, they all sound.
  • Large homes may need extra smoke alarms.
  • It is best to use interconnected smoke alarms. When one smoke alarm sounds they all sound.
  • Test all smoke alarms at least once a month. Press the test button to be sure the alarm is working.
  • Today’s smoke alarms will be more technologically advanced to respond to a multitude of fire conditions, yet mitigate false alarms.
  • A smoke alarm should be on the ceiling or high on a wall. Keep smoke alarms away from the kitchen to reduce false alarms. They should be at least 10 feet (3 meters) from the stove.
  • People who are hard of hearing or deaf can use special alarms. These alarms have strobe lights and bed shakers.
  • Replace all smoke alarms when they are 10 years old