Editing Security alarm (section)

===Smoke, heat, and carbon monoxide detectors===
Most systems can also be equipped with smoke, heat, and/or [[carbon monoxide]] detectors. These are also known as 24-hour zones (which are on at all times). Smoke and heat detectors protect from the risk of fire using different detection methods. Carbon monoxide detectors help protect from the risk of carbon monoxide poisoning. Although an intruder alarm panel may also have these detectors connected, it may not meet all the local [[fire safety#Fire code|fire code]] requirements of a fire alarm system.

Traditional smoke detectors are ionization smoke detectors which create an electric current between two metal plates, which sound an alarm when disrupted by smoke entering the chamber. Ionization smoke alarms can quickly detect the small amounts of particles produced by fast-flaming fires, such as cooking fires or those fueled by paper or flammable liquids. A newer type of the smoke detector is the photoelectric smoke detector. It contains a light source, which is positioned indirectly to the light sensitive electric sensor. Normally, light from the light source shoots straight across and misses the sensor. When smoke enters the chamber, it scatters the light, which then hits the sensor and triggers the alarm. Photoelectric smoke detectors typically respond faster to a fire in its early, smoldering stage, before the source of the fire bursts into flames.