FIRE ALARM INSTALLATION
A fire alarm system is generally required to be installed as part of fire certificate required by the Fire Precautions Act or the workplace regulations after an audit of a fire risk assessment.
Planning the Fire Alarm System
The decision of whether a fire alarm system is required or the type of category should not normally be the responsibility of the designer, customer/installer. The local authorities should take these decisions for enforcing legislation in buildings. With all fire alarm systems there should be an exchange of information and decision process a typical example would be.
★Building control officers
★Statuary and insurance requirements
When sufficient information and level of category has been obtained then the fire alarm system can be designed.
There are different types of smoke detectors:- optical/multi-sensor, Ionisation and beam detectors.
Optical: Optical smoke detectors operate on the principal of infra red light refracting off smoke particles entering the chamber. This
makes this type of detector more sensitive to smouldering fires such as modern fabrics or furnishings. Optical detectors are more
prone to false alarms from steam or dusty environments (outside bathroom/building works).
Beam Detectors: Beam detectors comprise of a transmitter and receiver. The transmitter emits an infra red beam from the TX (transmitter) to the RX (Receiver), the beam detects obscuration by the smoke.
Ionisation: Ionisation detectors operate on the principal of charred smoke particles passing between two electrodes causing a small current flow. This makes this type of detector more suitable for fast flaming fires such as paper/wood. Ionisation detectors are more prone to false alarms from burning smell i.e. outside a kitchen.
There are two main types, rate of rise & fixed temperature.
Rate of rise heat detectors will respond to a sudden increase in temperature but also have a fixed element in case of a slow smouldering fire. Rate of rise detectors are most suitable for areas where a smoke detector is undesirable i.e. staff room.
Fixed temperature heat detectors have a sensing element fixed at a particular temperature, when this is reached, the detector operates. Fixed temperature is ideal for kitchens, boiler room where a rate of rise heat detector would be unsuitable.