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How Does a Photoelectric Smoke Detector Work

Did you know that approximately 2,755 people were killed in residential fires in 2013 (National Fire Protection Association)? You'd be surprised to know that more people are killed by smoke inhalation than by burns, which means that heat and smoke from a fire are more dangerous than the fire itself.

So how do you protect your home and family from fires? Install smoke alarms! Smoke alarms can detect fumes and smoke coming from a fire, way before you are able to detect the danger. According to the Kentucky Injury Prevention and Research Center, 13 out of 14 homes in the US have smoke alarms installed.

What is a photoelectric smoke detector?

There are different types of smoke alarms you can choose from. Photoelectric smoke detector is one of the most commonly installed smoke alarms. This alarm is more responsive to smoldering fires as it is designed to detect smoke and fumes from a fire. This type of detector could buy you sufficient time to escape the premises in case of fire.

How does it work?

A photoelectric smoke detector operates on a basic light scattering principle or a light obstruction principle. Here are the details:

Light scattering principle

A photoelectric smoke detector which uses the light scattering principle is typically made up of a light diode and a sensor, which are positioned to one another at a certain angle in the chamber. Due to the angle, the light beam will not directly reflect onto the sensor. When smoke enters the chamber, the smoke particles disrupt the beam of light being emitted, causing it to scatter and reflect on the light sensor. As soon as the light sensor detects the particles of light, it will immediately trigger the alarm.

Light obstruction principle

A photoelectric smoke detector which uses the light obstruction principle is made up of a light source and a light sensor placed inside the chamber. In the event of a fire, smoke particles would block the light beam. The light sensor will detect the light's sensitivity, and would raise the alarm if the beam of light falls below a certain frequency threshold.


Photoelectric smoke alarms can detect smoldering fires and give you enough time to escape. But such alarms can also lead to false alarms. It is recommended that you install a smoke alarm at least 10 feet away from kitchen appliances to reduce the risk of false alarms. However, it is important that you have smoke alarms installed in every floor of your home.