What Does a Smoke Detector Detect?

Ionization Detection

• Most domestic smoke detectors use ionization detection to pick up the presence of smoke and set off an alarm. Ionization-type detectors contain a small ionization chamber placed between two electrodes. Smoke particles entering the chamber interrupt the current running between the electrodes, which triggers the smoke alarm.

Optical Detection

• Optical smoke detectors use a narrow beam of light and a photoelectric sensor to pick up the presence of smoke. In the event of fire and smoke, the path of the beam is interrupted and scattered by the smoke particles, which triggers the smoke alarm. Offices and public buildings often use optical smoke detectors.

Air Sampling Detection

• Air-sampling smoke detectors identify microscopic smoke particles in the atmosphere. The systems suck in air through a network of small pipes installed in ceilings. The air passes a laser detection device that recognizes microscopic smoke particles and triggers the alarm. More expensive and advanced than domestic smoke detectors, air sampling smoke detection is used in business and industry.

Carbon Monoxide Detection

• Some domestic and industrial smoke alarms use carbon monoxide detection. Highly toxic carbon monoxide gas is a byproduct of combustion. Smoke alarms with carbon monoxide sensors trigger when the level of carbon monoxide in the atmosphere exceeds a certain threshold. Some ionization or optical detection smoke alarms include a carbon monoxide sensor as a supplementary system.