How can you detect a fire?

Fire detectors do not detect the presence of fire, rather they detect heat or smoke depending on the type of detector. Smoke detectors have a light inside which shines on a receiver when smoke is present in the room it rises up and causes a break in the light therefore activating the alarm, this also makes it common for false activations in these types of alarms due to dust and dirt in the air. Heat detectors on the other hand have a small plate on the outside which is temperature sensitive. Heat detectors can be reactant to different levels of heat depending on what their use it. Usually they are made to activate at around 185 degrees F. When the ambient temperature reaches this (very low temperature for a fire) the metal plate will melt off its contact points therefore activating the alarm. These are just two types of detectors.