The SAFE-T-ALERT™ 35 Series combination CO/Gas alarm is an alarm that combines into a single compact system, a powerful alarm that detects both Carbon Monoxide (CO) and explosive Propane (LPG) gas. The 35 Series uses the latest microprocessor technology combined with two electronic self-cleaning sensors that operate independently of each other. The combined unit can detect both CO and explosive gases simultaneously. This detector is listed as a CO and Propane gas detector for RV use. Other explosive gases such as acetone, alcohol, butane, and gasoline may cause false alarms. To prevent false alarms from brief "puffs" of gas, the detector has a recheck cycle before alarming. If high levels of gas remain during the recheck cycle, the detector will alarm. The electronic CO sensor in your SAFE-T-ALERT™ CO alarm is very sensitive to CO gas. It will not react to safe levels of most other gases.