Optical Smoke Detector

Definition - What does Optical Smoke Detector mean?

An optical smoke detector, also called a photoelectric smoke alarm, is a type of smoke detector that uses optical light to detect the presence of smoke. These devices contain a light emitter, which may be optical, infrared, or ultraviolet light, as well as a light sensor. If smoke crosses the light beam, the intensity of the light that hits the sensor will be reduced, triggering the alarm.

Optical smoke detectors are one of two primary types of smoke detection alarm, along with ionizing smoke detectors. The use of smoke detectors is required by occupational health authorities such as OSHA, as well as fire protection organizations such as the National Fire Protection Association, which sets minimum standards for the use of alarms under its NFPA 72 standard.

Safeopedia explains Optical Smoke Detector

A typical optical smoke alarm contains a small chamber for smoke to enter, which houses the light beam and sensor used to monitor for smoke. In larger buildings, such as auditoriums, the detection unit may consist of separate light beam and sensor devices instead of a single unit. Both types of systems are activated when the minimum light intensity hitting the sensor falls below a certain threshold. This threshold is designed to prevent false alarms while maintaining sufficient sensitivity to the presence of smoke.

The usefulness of a particular type of fire detection system varies depending on the type of fire it is being used to detect. Optical smoke detectors are useful for the quick detection of fires that begin with a period of smoldering, while ionizing smoke alarms—which rely on an ionizing beam and a sensor that detects ionized smoke—work better for detecting fast-growing fires. Because different smoke alarms are more effective under some conditions than others, the NFPA recommends the use of combination alarms that either use both types of detection systems or that use either system in combination with a different fire detection method (such as heat detection).

The correct use of fire detection and alarm systems is an integral part of modern occupational safety systems. As such, their use is required by advanced regulatory agencies throughout the world. OSHA’s “Fire Detection Systems” standard (29 CFR 1910.164) provides a number of minimum requirements for the use of smoke alarms in the workplace, including where they must be deployed and how often they must be inspected, tested, and maintained.

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