Low profile compact round battery powered photoelectric smoke and CO combo alarm with silence feature. Tamper resistant, alarm locks to mounting bracket to prevent removal of battery and/or alarm. Powered by sealed, ten year lithium batteries to provide continuous protection for ten years without battery replacement. Photoelectric smoke sensing technology. Electrochemical CO sensing technology. 10 year CO sensor and 10 year end of life. Provides audible notice when alarm needs to be replaced.