Monitor your Indoor Air Quality. A colour change tells you whether the air you are breathing is safe from carbon monoxide. Minimum of 18 months operational life. Patented biomimetic technology reacts to the presence of CO in manner similar to the human body. Detects and gives a visual normal, caution, or hazardous condition indication. Works reliably at the broadest range of humidity and temperature. Specific to CO only, will not sense normal levels of environmental gases. Protectively packaged sensor protects the unit from accidental household chemicals being directly sprayed on the sensor.