Fire Detection and Alarm Systems: A Brief Guide (part 3)


There various types of fire detectors. The major ones are smoke, heat, and flame detectors. Within each type are a lot of additional specific types. Here we are discussing the most popularly used for building fire detection and alarm activation.

Heat detectors are the most basic type of detectors. They are produced in several types which are divided into two main categories; line and spot. Line detectors provide a continuous detector through all areas of the coverage. Spot detectors are single units which are installed in single locations of the protected area. While spot detectors are more widely used, line detectors are usually reserved for special situations.

Spot detectors are most commonly rate-of-rise, fixed temperature, or a combination. Rate-of-rise detectors are activated based on the rise speed of the temperature, not a fixed point. Fixed temperature detectors operate at a specific temperature. These two types of detectors are most suitable for the areas which may get hot even under normal conditions, for example, detectors in a warehouse which is not temperature-controlled.

Smoke detectors are available in many types. Photoelectric smoke detectors are activated based upon light scattering within the detector’s detection chamber. Light is projected through the detector’s chamber and then will be scattered if striking smoke. This light is detected by a photocell.

Ionization smoke detectors are the most common in home use. They detect the particles in smoke. When smoke passes through the detector’s chamber, the particles are ionized. These particles may be detected later by the charged plates in the detector. There are smoke detectors combined with a heat detector. The beam detector operates when obscuring smoke between the laser receiver and emitter interrupts the beam. These detectors are often used in large open spaces.

The air sampling detection system uses the tubing which is placed throughout the protected area. The tubing has small holes that are spaced out along the tube’s length and the air is drawn constantly into the unit, which can detect low levels of combustion products.