First Alert, Battery Operated Combination Photoelectric Smoke & Carbon Monoxide Alarm, The SMCO200V Battery-Operated 2-in-1 Smoke Alarm & Carbon Monoxide Alarm provides reliable protection against both threats. Alarm features voice and location alerts and meets new industry standards. Electrochemical Sensor That Detects Carbon Monoxide Leaks From Multiple Sources Such As Faulty Fuel Burning Appliances & Blocked Chimneys, Sleekly Designed, Can Be Mounted Unobtrusively On A Wall Or Ceiling, A Loud Alarm Sounds When Smoke Or Carbon Monoxide Is Detected As Well As A Voice Alert Warning Of The Location & Type Of Danger, NOTE: Please Check Your Local Building Code Requirements Before Installing This Product To Determine Compliance With Applicable Standards.