Fire detectors are essential components of a fire safety system because they provide early warning of fire by sensing smoke, heat, flame, or combustion products. Early detection allows occupants to evacuate safely and enables firefighting measures to begin before the fire becomes uncontrollable. Different types of detectors operate on different principles and are selected according to the nature of the building, occupancy, environmental conditions, and expected type of fire. Smoke detectors are among the most widely used fire detectors. They detect smoke particles produced during combustion. The two major types are ionization and photoelectric smoke detectors. Ionization detectors contain a small ionization chamber and are generally sensitive to rapidly developing flaming fires. Photoelectric detectors use a light source and a sensor; smoke particles scatter the light and activate the alarm. Smoke detectors are commonly installed in homes, offices, hotels, hospitals, and other occupied buildings. Heat detectors operate by sensing an increase in temperature. They are useful where smoke detectors may produce false alarms because of dust, steam, fumes, or other environmental conditions. Fixed-temperature heat detectors activate when the surrounding temperature reaches a predetermined level. Rate-of-rise heat detectors respond when the temperature increases rapidly within a