Fire Detectors are used to detect smoke, flames or heat in a building as an early warning of fire. Types of detectors include beam detectors, flame detectors, heat detectors, multisensor detectors and smoke detectors.

Beam Detectors project a beam of infra-red light, the beam detector then registers the light and produces an electric signal. The electric signal of the beam detector is then processed by the detector which generates alarm or fault signals if any smoke or harmful substance distrube the light beam.

Detector Testers are used to test all types of detectors including smoke detector testers and heat detector testers. Smoke detector testers work by releasing test smoke into the detector to test it whether it is working properly. Heat detector testers work by altering the ambient temperature around the detector to test it whether it is working correctly.

A flame detector is a detector that uses optical sensors to detect flames. There are two general types of flame detectors, Infrared Flame Detectors and Ultraviolet Flame Detectors.

A heat detector is a device that responds to changes in ambient temperature. If the ambient temperature rises above a predetermined threshold an alarm signal will be triggered. Heat detectors can be divided into two main classifications of activation, "rate-of-rise" and "fixed" however most sophisticated units are activated by both conditions.

In fire safety, multi sensor detectors combine multiple detection signals that a fire has started, such as the levels of heat and ionisation, as opposed to specialising in only one. In order to detect a fire in the quickest possible amount of time, an alarm sensor has to detect the products of combustion from a particular type of fire. However, one detector might be great at picking up smoke particles from a synthetic materials fire for example, but not work well at detecting the heat from a rapidly progressing liquids fire. The advantage of multi sensor detectors is that they quickly sense when different types of fires have started. Multi sensor detectors are normally triggered by many more types of fires than single sensor detectors.

Commercial, industrial, and mass residential smoke detectors detect smoke and issue a signal to a fire alarm system. Smoke detectors work either by optical detection (photoelectric) or by physical process (ionization) or by both detection methods to increase sensitivity to smoke. Smoke detectors in large commercial, industrial, and residential buildings are usually powered by a central fire alarm system, which is powered by the building power with a battery backup.