Fire Alarm and Detection: Smoke and Heat Detectors

Home security is not only concerned with preventing burglary and other criminal attacks on the home, it also involves the safeguarding of lives and properties in the home against fatal accidents such as fire outbreaks. A fire alarm and detection system is designed to detect fire outbreaks in buildings and send out an identifiable alarm to the concerned parties. The system consists of smoke detectors, heat detectors, control and repeater panels, alarm bells and break glasses.

What Are Smoke Detectors?

Smoke detectors are devices capable of detecting or sensing smoke and signalling a warning to either the homeowner or the fire authorities, depending on the manner in which it was programmed. There are basically two types of smoke detectors: ionization and photoelectric smoke detectors.

ionization-detectorThe ionization detector uses the theory of electric circuit as its operating principle. The ions and electros in the chamber of the detector move between two electrodes, thus creating an electric current. However, during a fire outbreak, smoke particles attach themselves to the ions and the current ceases to flow. Once this happens, the sensor is tripped and the home owner alerted.

photoelectric-smoke-detectorIn the photoelectric or optical detector, a beam of infrared or ultraviolet light is emitted and reflected back. If the intensity of the light reflected back is lesser than the light emitted, due to smoke or other air-borne substances absorbing part of it, the smoke sensor is tripped and the alarm alerts the owner.

Comparisons Between Optical and Ionization Smoke Detectors

1. The ionization smoke detector is cheaper than its optical counterpart.

2. Ionization smoke detectors are more prone to false alarms than the optical ones.

3. Optical smoke detectors are more responsive to smoldering fires than blazing flames, while ionization smoke detectors respond faster to blazing 4. The optical smoke detector is more reliable for detecting smoke at both the smoldering and flaming stages of fires.

5. Optical smoke detectors are less likely to be mistakenly deactivated by the home owner.

On the whole, fire safety experts and authorities advise home occupants to purchase optical (photoelectric) detectors, as they are more effective than the ionization detectors. Combination detectors that use both the ionization and photoelectric processes are also recommended.

Smoke detectors should be installed in every bedroom and hallway. They should not be placed in the bathrooms, toilets, kitchens, laundry room and the garage. One smoke detector is sufficient for each room, as long as the room’s area is less than 100m 2 . Once the area of the room is equal to or greater than 100m 2 , then two smoke detectors are placed in the room.

What Are Heat Detectors?

These are devices that detect or sense a change in temperature in a space and alert the concerned parties. Heat detectors are placed in rooms or spaces where there would naturally be smoke or mist, such as kitchens, enclosed car parks, bathrooms and toilets, laundry rooms, garages and generator houses.

For ideal residential fire protection, the combination of smoke and heat detectors is recommended.