What is the difference between Photoelectric and Ionization smoke alarms?
• Ionization Smoke Alarms – Generally are more effective at detecting flaming fires, which consume combustibles quickly and spread rapidly. Sources of these fires include paper burning in a wastebasket, or grease fires on a stove. • Photoelectric Smoke Alarms – Generally are more effective at detecting smoldering fires, which smolder for hours before bursting into flame. Sources of the fires include cigarette smoldering in couches or bedding. Why does the National Fire Protection Association (NFPA) recommend that home smoke alarms be replaced after 10 years? Like all devices with electronic components, smoke alarms have a limited effective service life. As electronic devices, smoke alarms are subject to random failures. In 10 years there is roughly a 30% probability of failure before replacement. After 15 years, the chances are better than 50/50 that your alarm has failed. That is too big a risk to take. Replacing alarms after 10 years protects against the accumulated chance of failure
• Ionization Smoke Alarms – Generally are more effective at detecting flaming fires, which consume combustibles quickly and spread rapidly. Sources of these fires include paper burning in a wastebasket, or grease fires on a stove. • Photoelectric Smoke Alarms – Generally are more effective at detecting smoldering fires, which smolder for hours before bursting into flame. Sources of the fires include cigarette smoldering in couches or bedding. For maximum protection, install both types of smoke alarms on every level of the home.
There are two types of smoke alarms available today: Photoelectric Smoke Alarms and Ionization Smoke Alarms. Both types of alarms provide adequate protection against fire. • Ionization detectors respond more quickly to flaming fires with smaller combustion particles • Photoelectric detectors respond more quickly to smoldering fires • Combination smoke alarms featuring both photoelectric and ionization technology are also available. When smoke enters a photoelectric alarm, light from a pulsating light source in reflected off the smoke particles onto a light sensor, triggering the alarm. When smoke enters an ionization alarm, ionized air molecules attach to the smoke particles and reduce the ionizing current, triggering the alarm.
