There are generally two types of smoke detectors - ionization smoke detectors and photoelectric smoke detectors. Smoke particles of a varying number and size are produced in all fires. Ionization smoke detectors are generally more sensitive than photoelectric smoke detectors at sensing small particles, which tend to be produced in greater amounts by hot, flaming fires, that are consuming combustible materials rapidly and may spread quickly. Sources of these fires may include paper burning in a wastebasket, or a grease fire in the kitchen. Photoelectric smoke detectors are generally more sensitive than ionization smoke detectors at sensing large smoke particles, which tend to be produced in greater amounts by smoldering fires, which may smolder for hours before bursting into flame. Sources of these fires may include cigarettes burning in couches or bedding. For maximum protection, use both types of technology on each level and in every bedroom of your home.