While all smoke alarms are designed to detect smoke, different sensing technologies react differently to certain types of fires. This alarm makes use of both ionization and photoelectric sensors to offer the earliest possible warning--regardless of the type of fire. Sometimes a fire can smolder for hours before erupting into flames. Photoelectric Sensing Technology is more sensitive than Ionization Sensing Technology at detecting these sorts of smoldering fires, like those caused by cigarettes burning in couches or bedding. Other fires erupt into flames quickly, like kitchen grease fires or fires fueled by paper burning in a wastebasket. Ionization Sensing Technology is generally more sensitive than Photoelectric Sensing Technology at detecting these sorts of flaming fires.