How does a smoke detector work?

Smoke detectors can be divided into three different types, which work in different ways. We explain the photo-optical smoke detector, the thermo-optical smoke detector and the ionization smoke detector.

What is a photo-optical smoke detector?

Most private homes have since the smoke detector duty on photo-optical devices, also called photo-electronic smoke detectors. They have a lightless smoke chamber, which has some openings for the ingress of smoke.

In this chamber constantly radiates a small infrared lamp. The light beam breaks through penetrating smoke, hitting a sensor that is normally unirradiated by the light. The next moment the sensor triggers the alarm.

The sensor is shielded from all external light by the special construction of the outer shell and by non-reflective material to avoid false arms.

How does a thermo-optic smoke detector work?

As the name suggests, they focus not only on optical phenomena, but also on the thermals (heat development). They have both an infrared beam with sensor and a heat meter, a thermistor.

If the temperature rises quickly or if it gets overly hot overall, they sound the alarm. The thermistor conducts the current much better at a high temperature than at normal temperature.

Pure heat detectors are not suitable for private homes because they react too slowly. The optical component is therefore a "must" to be quickly alerted in case of emergency.

The operation of the ionization smoke detector

The ionization smoke detector has two metal plates containing a radioactive element in their middle. The alpha and beta rays emanating from this element allow a weak current to flow inside.

Entering smoke binds a part of the flowing ions by means of electrostatic attraction, the current weakens. The smallest amount of smoke already triggers the alarm. However, you should not dispose of such a device in the household waste, it belongs to the special waste!

Which is the best smoke detector for the home?

The photo-optical smoke detector is rightly the most popular detector in the private sector. The thermo-optical devices offer no special added benefit, but are more expensive. The ionization smoke detectors offer the highest sensitivity, but contain hazardous waste.

Tips & Tricks

Do not install your smoke detector in attic rooms at the top of the roof, but at least 0.5 m away from the slope. Air cushions often obstruct the rise of the smoke to the ceiling!

Video Board: How do Smoke Detectors Work