How does fire alarm system function in practice?
23.12.2024
Fire alarm system is a hardware complex designed for early detection of fire points, elevated temperature or smoke in buildings and structures. Upon detecting an emergency, the system transmits signals to activate other hardware, such as warning systems, fire extinguishing and smoke exhaust systems.
Regardless of the detection method, when the alarm is activated, an audible alert sounds to warn people in the building of a potential fire. This ensures that appropriate measures can be taken to manage the risk and evacuate people.
Principle of operation
Generally, fire alarm system, combined with other systems, functions as follows:
- In case of early fire indicators (smoke, sudden temperature rise, open flame, etc.), the detection device (sensor or detector) is activated.
- It transmits signal to the fire alarm control device. The signal can be transmitted through manual fire alarm activators, enabling the “human factor” to aid in early fire detection.
- The fire alarm control device receives signals from sensors, processes them automatically based on the system’s programmed algorithm, manages the facility’s engineering systems, activates other fire protection systems, and alerts fire safety personnel.
- The fire alarm control device simultaneously activates the fire warning and evacuation management system.
- The elevator automation and access control systems are activated. The elevators automatically return to the first floor, and all doors are unlocked to enable evacuation.
- The necessary conditions for safe evacuation of people are ensured by the operation of the smoke control system.
- To combat the fire at its initial stage, the fire extinguishing system and internal fire water supply are activated.
Types of fire alarm systems
- Non-addressable fire alarm systems are often installed in small facilities. Upon detecting fire, such systems activate alarm signals that cannot pinpoint the exact location of the emergency. They are characterized by a relatively low cost but have a high probability of false signals.
- Addressable systems are typically installed in medium and large facilities. Unlike non-addressable systems, they enable accurate pinpointing of the source of a fire or smoke.
- Addressable analog complexes constitute the most expensive and reliable type of fire alarm system. They may include a variety of hardware, allowing for accurate localization of the emergency, determination of its nature, and minimization of false alarms.
Types of fire sensors / detectors
Fire sensors (detectors or sensors) are divided into four main types:
1) Fire alarm thermal detector
Thermal fire detector responds to temperature fluctuations. They are classified into:
- Fixed-temperature – with a set temperature threshold that activates the sensors.
- Integral – react to a sharp rise in temperature.
Fixed-temperature fire detectors are less effective because they activate at a 70°C threshold. One of the advantages of this type is its affordability.
Integral fire detectors allow for early fire detection. The disadvantages include their high cost, as they contain two thermoelements and an integrated signal processing system.
Thermal fire detectors should be applied only when heat is the main characteristic of a fire.
2) Smoke fire detectors
They react to smoke particles in the air. Smoke detectors operate on the principle of infrared radiation dispersion by smoke particles. A drawback of this detector is that it can activate in the presence of high levels of steam or dust in the room.
3) Flame sensors
Detectors of this type identify open flames or smoldering. They should be installed in areas where fires are likely to occur without preceding smoke. They are more effective than the two previous types of detectors, as they detect flames at an early stage, even before smoke or a significant temperature rise occurs.
4) Combined fire detectors
These systems combine multiple fire detection techniques. Typically, combination detectors contain both a smoke sensor and a heat sensor. This allows for more accurate identification of fire signs and sending alarm signals to the central monitoring console.
Conclusion
Effective fire protection in a building depends on proper sensor placement, the use of the right detectors in specific areas, and the quality of fire detectors.
The effectiveness and reliability of fire detectors depend on their quantity, type, installation location, and operating conditions.