How Do Smoke Detectors Work?

Smoke due to a fire outbreak can be hazardous to both lives of people present on the premises as well the materials and assets on the worksite itself. Also, the carbon monoxide that may be produced can be quite lethal. A reliable and efficient way to detect fire is by using a smoke detector. We will now take a look at how this device works.

Working of an Optical Smoke Detector

An optical smoke detector is usually installed on the ceiling, as the smoke usually travels upwards when something begins to burn. As the fire generates hot gases which are lighter than ordinary air, they begin to rise along with tiny particles of soot and smoke. The smoke detector has a big opening at the bottom, which opens out into the detection chamber. An infrared light beam, which is invisible, is projected across the chamber from an LED or a light-emitting source to a photocell. The photocell is an electronic light detector. This generates electricity as long as the light falls on it.  When there is no smoke, the light beam is constant between the detector and the LED indicating that everything is fine and the alarm is silent.

However, in the case of a fire outbreak, smoke enters the compartment and the light beam is interrupted. Since there is no light falling on the photocell, no electric current is generated and the alarm is triggered.

Working of an Ionisation Smoke Detector

Ionisation smoke detectors work on a completely different principle when compared to optical smoke detectors and are less expensive too.

An ionisation chamber is located inside the detector that is filled with ions and is open to the air. Inside the chamber, a small piece of radioactive material, Americium is placed, which emits radioactive or alpha particles that enters the detection chamber. These collide with air molecules and are converted into ions with a positive charge and electrons that are negatively charged. The electrons and ions move in opposite directions between two electrodes and cause a current to flow between the electrodes and a circuit is completed.

When there is an outbreak of fire, smoke particles enter the detector and block the ionisation chamber. The electric current stops as the smoke particles attach themselves to the ions. The circuit is broken and the alarm is activated.

When the fire is put out, the smoke stops and the detection chamber clears, the ions begin to move between the electrodes once again and the circuit shuts down and the alarm also stops.

Ionisation smoke alarms are better in case of flaming fires, while photoelectric alarms provide quicker response to smouldering and slow burning fires. The best option would be to choose a smoke detector that has both ionisation as well as photoelectric detectors to cover a range of fires and provide better protection.

Today, Cygnus products are redefining safety standards and the top-of-the-range Cygnus smoke detectors go a long way in ensuring the safety of the worksite and workforce.