The Heiman HM-638PHS Photoelectric Smoke Alarm provides reliable 24/7 monitoring for your home and family against fast-flaming and smoldering fires. This advanced alarm features an industry-leading 10-year sealed lithium battery that eliminates the need for frequent battery replacements, ensuring continuous monitoring for a full decade. It uses a high-sensitivity photoelectric sensor that quickly detects visible smoke particles from smoldering fires, reducing false alarms from cooking fumes. The alarm is UL 217 Latest Edition certified for safety and performance, and can be installed in just 3 minutes without any special tools or electrician help. A low battery warning system alerts you when the battery is running low, so you never have to worry about being unprotected. Meets requirements of 10th Edition UL 217, FCC, and CSFM.