smoke detector smoke alarm

smoke detector smoke alarm

Photoelectric Smoke Detectors vs. Ionization Smoke Detectors

The crucial difference between a photoelectric smoke detector and an ionization smoke detector is the mechanism for detecting fires. Ionization detectors use a small piece of radioactive matter to create a current between two electrodes in the sensor. Smoke particles that get into the sensor interfere with the current. When the electrodes sense a current drop, the alarm starts to sound.

Ionization smoke detectors operate because they have a small amount of radioactive material which is located in between two electrically charged plates. This ionizes the air which creates a current to flow in between the two plates. This flow of ions is disrupted when smoke enters the chamber. The reduction in the flow of current activates the alarm. Ionization smoke alarms tend to respond quicker than photoelectric smoke detectors to smoke that is produced from a flaming fire, although will not signal an alarm until a fire has become sufficient enough to produce enough smoke to reach the alarm.

Photoelectric smoke detectors operate with a continuous, focused beam of light onto a mirror from an LED light source that is aimed directly into a sensing chamber, away from the sensor. If smoke enters the chamber, the light that is reflected onto the light sensor is interrupted, scattering light in many directions and triggers the alarm. Photoelectric smoke detectors tend to respond quicker than ionization smoke alarms to smoke that is produced by a smoldering fire. Photoelectric smoke detectors can detect smoke before a fire even begins to appear.

Photoelectric smoke detectors are still relatively uncommon but may be the ideal choice in several situations. Generally speaking, photoelectric detectors are best for detecting fires that do not produce high quantities of flame. These include smoldering fires from things like cigarette butts or candles. The leading cause of death from fire is actually smoke inhalation, and photoelectric detectors can identify these kinds of fires before the flames even start.

Ionization detectors, on the other hand, are better for fires with large flames that do not produce as much smoke as smoldering fires. Ionization detectors are especially useful for fires from sources like wood, paper, or flammable liquids. These detectors can give you more time to react to and escape from high-flame fires.

Benefits of Photoelectric Smoke Detectors

Below are some of the main benefits of choosing a photoelectric smoke detector.

Wider Range of Detection

Photoelectric smoke detectors may be best for homes because they can accurately detect a wider range of fires. Many fires in the home start as smoldering ashes, and the low heat prevents ionization detectors from detecting them. Photoelectric detectors are better at detecting these fires that can linger until they turn into large, destructive flames.

Fewer False Alarms

Ionization false alarms can trigger from several non-fire sources, such as cooking and steam from the bathroom. Anything that increases heat could potentially trip the alarm. Conversely, a photoelectric smoke detector false alarm would be relatively rare because smoke particles must scatter the light beam before it goes off.

No Radioactive Material

Ionization smoke detectors contain a small amount of radioactive material, most commonly americium-241. The level of radiation is small enough that it does not pose a risk to human health. However, photoelectric detectors are an option for homeowners who want to minimize radiation exposure.

photoelectric smoke detectors chart
Photoelectric smoke alarms are generally more responsive to fires that begin with a long period of smoldering (called “smoldering fires”). How they work: Photoelectric-type alarms aim a light source into a sensing chamber at an angle away from the sensor. Smoke enters the chamber, reflecting light onto the light sensor; triggering the alarm.

Ionization smoke alarms are generally more responsive to flaming fires. How they work: Ionization-type smoke alarms have a small amount of radioactive material between two electrically charged plates, which ionizes the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of ions, thus reducing the flow of current and activating the alarm.

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