It is a device that is used at a very high rate in fire detection systems due to its ability to detect most types of fires at their beginning. These devices are classified into three categories:

1- Ionic smoke detector: which senses visible and invisible smoke and also senses small suspensions that fly upward due to heat. It is used in paper fires, for example, because burning is rapid.

2- Optical smoke detector: which senses visible smoke and large suspensions that fly upwards due to heat and is used in places where there are cables or PVC materials, but it is sensitive to cigarette smoke or the like.

3- Smoke detector within the air conditioning system ducts (return air ducts)

Factors that affect the performance of the smoke detector:

· Fumes, dust or humidity.

· Air current at a speed greater than 1.5 meters / second.

· Paint fumes, detergents or chemicals, air fresheners and strong odors.

· Excessive smoking or the like.

· Vibrations or shocks.

· Insects.

· Magnetic field or radiation.

· Ceiling height.