The effectiveness of controlling and extinguishing a fire depends on the time elapsed from the appearance of the threat to its detection and the initiation of firefighting actions. Quick detection of a fire reduces material damage and requires fewer resources to control the fire. The highest efficiency in this regard is achieved with Permanent Fire Protection Systems combined with effective detection and activation systems. Therefore, modern fire detection and control systems are crucial components of a building’s fire protection equipment.
How do detection systems detect a fire?
The primary components responsible for detecting a fire are fire detectors. These devices continuously or periodically analyze the air within protected areas for signs of fire. Key factors in selecting fire detectors include not only installation costs and legal requirements but also the likelihood of fire development in its early stages, the architecture of protected spaces, environmental conditions (ventilation, heating, humidity, dust), and, most importantly, the type of materials stored.
The four main types of detectors are:
- Aspirating Smoke Detection Systems (ASD): For example, VESDA detectors are among the most sensitive devices used for fire detection. They work effectively in the early stages of a fire—during the smoldering phase when the first combustion products are present in the air. These detectors work by drawing air from the protected area for analysis. When combustion products are detected, an alarm signal is sent to the fire control panel.
- Smoke Detectors: These detectors analyze the air for aerosol particles resulting from combustion or thermal decomposition, i.e., when smoke is visible. Optical smoke detectors, which use light absorption and scattering phenomena, are currently the most commonly used. If smoke partially absorbs the light beam emitted by the detector, it triggers an alarm. While popular and cost-effective, optical smoke detectors may be less effective in environments with high dust levels, significant vapor presence, or high humidity, potentially leading to false alarms.
- Flame Detectors: These devices detect infrared and ultraviolet radiation emitted by flames. They are used primarily for monitoring areas where materials produce minimal smoke during combustion or for protecting open spaces where other detectors may be ineffective. Flame detectors work by selecting the frequency of the flame’s flicker. They should be avoided in areas with modulated sunlight due to moving trees or radiation from industrial processes, which can interfere with their operation.
- Heat (Temperature) Detectors: Effective during the heat phase of a fire, when the thermal energy from the fire spreads to the detector. An alarm is triggered when the rate of temperature increase or the temperature reaches preset levels. Heat detectors should not be used in environments where conditions exceed the thresholds set by the manufacturer, such as maximum temperature or humidity. They are also unsuitable for areas divided into multiple fire zones, where rapid air movement can carry hot air from the fire zone to adjacent areas.
