Automatic fire detectors can save lives and property. Their main functions are to quickly identify a developing fire and alert building occupants. When installed and maintained correctly, fire detectors are vital to preventing deaths and injuries.

There are five types of fire detectors: heat, flame, ionization, photelectric, and ionization/photoelectric. The difference between them is in the way the unit uses heat or smoke to detect fire. Selecting the right fire detector for the environment requires an understanding of how each type detects fire. The most common type of fire detectors are smoke detectors. A variety of heat and smoke detectors installed throughout the location can provide effective fire protection.

Heat Detector
Heat detectors use an increase in air temperature to detect heat and then sound an alarm. A heat detector takes longer to alarm than a smoke detector but has fewer false alarms. Heat detectors are a great selection for steamy, humid, or dusty environments because smoke detectors may false alarms in these kinds of environments. Heat detectors are also good selections for warehouses, storage locations, and infrequently occupied areas.

Flame Detector
Flame detectors use a line-of-sight device to look for specific types of light (infrared, visible, ultraviolet) emitted by flames during combustion. When the detector recognizes this light from a fire, it will cause the unit to alarm.

Ionization Smoke Detector
Ionization smoke detectors use disruption in an electrical current to detect smoke and then sound an alarm. Smoke disrupts a constant electrical current between two metal plates inside the unit causing it to alarm. Ionization smoke detectors are a great selection for environments where there is a possibility of fast-burning fires.

Photoelectric Smoke Detector
Photoelectric smoke detectors use disruption in a beam of light to detect smoke and then sound an alarm. Smoke scatters a beam of light inside the unit causing it to alarm. Photoelectric smoke detectors are a great selection for environments where there is a possibility of smoldering fires.

Ionization/Photoelectric Smoke Detector
Ionization/photoelectric smoke detectors combine both types of smoke detectors. Smoke disrupting either the electrical current or light beam will cause the unit to alarm. This type of smoke detector can detect fires that start as smoldering fires or flaming fires.

If your workplace uses a fire detection system designed and installed to meet the fire protection requirements of a specific OSHA standard, it must also comply with the Fire Detection Systems standard 29 CFR 1910.164.

General Guidelines for Placing Fire Detectors

  • Put at least one detector in each room, storage area, and hallway. You may need more than one detector per room for those that exceed the manufacturer's spacing requirements. For example, if your detector is rated for 30 feet, install detectors so they are evenly spaced with no more than 30 feet between them.
  • When only one detector is required in a room or space, place the detector as close to the center of the ceiling as possible.
  • Put at least one detector in each closet, elevator and dumbwaiter shaft, stairwell, and other enclosed spaces.
  • Place a detector at the top of each flight of stairs.
  • Place the detectors in the path of the air flow toward the return air duct when air supply or return ducts are present in a room or space.
  • Place all smoke detectors at least three feet from ceiling fans.

Over time, dust, dirt, and other foreign material can build up inside a detector’s sensing elements, resulting in reduced sensitivity, which can limit the amount of warning time given during a fire. Dirty or dusty detectors can also result in unwanted alarms that can desensitize occupants to the alarm system or produce more serious behavior (such as disconnecting the system altogether).

To avoid malfunctions and unwanted alarms and to make sure your fire detection system will perform as expected in the event of a fire, you are required to:

  • Operate and maintain your system in a working condition, making sure it is always turned on, except during repairs or maintenance.
  • Test and adjust fire detectors and fire detection systems often to ensure they operate correctly and maintain reliability.
  • Detectors found to be unreliable and/or with reduced sensitivity must be replaced or cleaned and recalibrated.
  • Assure that pneumatic and hydraulic operated detection systems installed after January 1, 1981, are equipped with supervised systems.
  • Have a qualified person service, maintain, and test all fire detection systems, including cleaning and necessary sensitivity adjustments.
  • Periodically have fire detectors cleaned of dust, dirt, or other particulates to ensure their proper operation.

All fire detection equipment must be returned to normal operation as soon as possible after being tested, used, or accidentally activated.