“Experience is the best teacher,”
says an old saying and continues “but the tuition is high.” The tuition in the field of fire prevention through history has been long lasting and has caused minor or major damage. Based on these experiences many laws, regulations and guidelines on fire protection were established. In addition to technical regulations, building regulations also need to be mentioned, as the fire prevention procedure begins with the design and construction of buildings. These regulations ensure that the buildings are constructed in such a manner that a potential fire cannot spread and can be effectively extinguished, and that people and animals can be rescued in case of emergency.
Proper and professional maintenance is recommended
If we leave out intentionally caused fires (sabotages, pyromaniacs…), the most common causes of fire are human negligence and technical device malfunctions usually caused by unprofessional interference, misuse and improper maintenance.
Improper maintenance means either that the system is not maintained at all, or that it is maintained by unauthorized and/or unqualified personnel. Other causes of fire fall within the scope of chemistry, the use of different technologies in modern industries which use highly flammable and explosive substances. In this case, fire may also cause an explosion if there is a flammable mixture of air and vapours of flammable substances present in the room.
Many fires arise from smouldering that can last for several hours before the flame erupts. The vast majority of fire victims die due to smoke asphyxiation or intoxication with toxic gases. Smoke is more dangerous than fire. Flue gases consist mainly of carbon dioxide and (in the case of incomplete combustion caused by insufficient supply of oxygen) also carbon monoxide. With modern fires there are not only wood and carbon compounds that burn, but also plastics and synthetic fibres, rubber, etc. The result is the presence of vaporised hydrochloric and hydrocyanic acid, hydrogen chloride, hydrogen sulphide, and other extremely toxic gases in flue gases. Non-toxic gases and vapours may cause death by suffocation as well if their concentration in the air makes the proportion of oxygen fall under 10%.
The early detection of fire is crucial
The extent of damage incurred in case of fire and the risk of injury or death depend on the time of its detection. When substances ignite and burn, they react very differently. A fire can start with an explosion or an immediate flame; it is also possible that smoke appears first (as with smouldering). That is why appropriate assessment of the most probable cause of fire and substances which might burn in a certain room is crucial; fire detectors should be selected accordingly.
When the firemen arrive at the scene of the fire and start putting it out, it is already too late to prevent damage from occurring. That is why timely fire detection and identification of the potential threat before the fire spreads is extremely important, as it helps limit damage as much as possible. The first devices which automatically detect changes in temperature signalling the start of a fire were made in the previous century.
Modern devices can detect smoke before temperature changes
Automatic fire detectors have been used since the 1960s. A fire is detected at the very start and firemen and other relevant departments are immediately notified; detectors can be set up to act independently as well (shutting down the air-conditioning devices and the inflow of air, opening the smoke vents, opening the path for safe evacuation and its automatic control). Modern devices do not react only to changes in temperature, which occur at a later stage in the fire, but also detect smoke beforehand. It is during the starting stages of a fire that the thickest clouds of toxic gasses are formed, which first spread over evacuation paths therefore posing the biggest threat to people.
Automatic fire detectors are similar to burglary detectors in the structure of their systems.
Fire alarm central control panel performs the following functions:
- power supply for the whole system, which is available for a certain amount of time during power failures as well,
- receiving fire signals from connected detectors and confirming their reception with audio and visual signals,
- forwarding the fire alarm to emergency services using the selected medium (phone network, optical connection…), or triggering the fire protection equipment using controllers and interfaces: shutting down oxygen supply, facilitating smoke and heat removal, activating fire extinguishing using appropriate methods, opening evacuation paths, turning on emergency lighting…),
- controlling the operation of the whole fire protection system; using audio and visual indicators to warn about system malfunctions (short circuit, power supply faults, status of back-up/auxiliary power supply, broken connections between detectors and the central control panel).
Modern fire detection, alarm systems and extinguishing systems come in different versions and allow for accurate pinpointing of the location of the fire – which detector triggered the central control panel. This is marked by an LED on the central control panel or by a message on the screen. Detectors are constantly connected with the central control panel and in pre-set time intervals monitor the required chemical and/or physical parameters which could indicate fire in the area that the detectors are monitoring.