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.