Smoke Detectors are early warning safety devices that detect smoke and sound an audible warning to inform the residents of a premise about an impending fire Hazard. Smoke Detectors are more popular than other heat and flame detection devices on the account that Inhalation of Smoke (Carbon Dioxide/ Carbon Monoxide) poisoning kills more people than burns.
There are two types of Smoke Detectors; Photoelectric Smoke Detectors and Ionization Smoke Detectors.
Photoelectric Smoke Detector
A Photoelectric Smoke Detector uses a light beam to detect fire. These types of alarms consist of a light-sensitive chamber. Inside the alarm chamber, a beam of light is shot through an LED device straight across the chamber. A consistent flow of light particles is the standard set of the detector. When smoke enters the chamber, it scatters the LED light from the straight path. The photosensor installed in a different compartment of the same chamber is triggered by the scattering of the light particles to sound the alarm.
Ionization Smoke Detectors
Ionization Smoke Detectors consist of two electronically charged plates and a small amount of radioactive material in between the two plates. The radioactive material ionizes the air inside the chamber and allows the flow of ions between the two plates. When the smoke fills in the chamber and displaces the ionized air, the flow of current between the two plates is disrupted and this triggers the alarm.
So, Which Type of Detector is better?
Broadly speaking, Ionization Smoke Detectors work slightly better in high flame situations whereas Photoelectric Smoke Detectors work better in the case of a smoldering fire.
To narrow it down in quantitative terms, in smoke alarm tests, Ionization Smoke Detectors typically will respond within 30 or 90 seconds faster in a high fast flame fire than a Photoelectric Smoke Detector. In the case of smoldering fires, Ionization Smoke Detectors respond an average of five to fifty minutes slower than Photoelectric Smoke Detectors.
High Flame Fires are typically fast-spreading fires that produce less smoke. Smoldering fire is either the early stages before a high
Flame fire or characterized as slow-moving fire with a significant amount of smoke and little flame.
According to NFPA, most of the deaths are caused by inhalation of smoke and not due to fatal burns. Carbon Dioxide and Carbon Monoxide poisoning incapacitate too quickly to make it to an otherwise accessible exit. Which makes smoldering fires much fatal than high flame fires. And based on tests, Ionization Detectors are only marginally more effective than Photoelectric Smoke Detectors even in case of high flame fires.
Besides, Ionization Smoke Detectors are notoriously infamous for false alarms and degrade over time as the radioactive material contained in them loses its potency.