One of the most important safety features in a home is the smoke detector. In the CSPC Residential Fire Loss Estimate report there were approximately 378,800 house fires in 2008. The major toll was the 2,390 lives lost from these incidents. So how do smoke detectors sense a fire?
How do Smoke Detectors Work?
Photo Beam Sensor
There are several different types of sensors. A photo beam smoke detector uses a low power laser and a light sensor to detect an interference. The beam of light is shot from the laser to the detector at all times. When smoke crosses blocks path the detector no longer senses the light and sounds the alarm. The problem with this setup is it takes a lot of smoke to block the sensor so it won’t be the fastest response.
Photoelectric sensors work in a similar fashion but the setup is switched to a 90 degree angle. The beam of light is shot past the detector at a 90 degree angle so that it won’t sense the light. When smoke makes its way into the unit it deflects the path of the light to hit the sensor. The advantage of this setup is the increased sensitivity to smoke.
The last smoke detector is the ionizing radiation type. It utilizes a tiny amount of americium-241, a radioactive element. The radiation process ionizes oxygen and nitrogen atoms passes through a chamber in the device. This reaction creates a small amount of current between two plates that is detected by the electronics. As smoke enters the chamber it disrupts the current and sets off the alarm.
Which is Best?
The National Institute for Standards and Technology (NIST) found that photoelectric models detected smoke approximately 30 minutes sooner than ionizing models (on average). That is a tremendous difference when your home and life are on the line.
Regardless of the type, make sure to schedule smoke detector maintenance on your monthly checklist. It only takes a couple minutes to clean the unit and test it. Be sure not to neglect this task as it is the best way of detecting a fire as soon as possible.