Ideal for Home, Office, Tunnels, Mines etc. The battery operated DCO 1001 features a new electro mechanical CO sensor with 3 points of auto calibration: 0, 100 and 500 ppm. The meter has a Backlit LCD Display and simultaneously exhibits Dual Readings of CO and Max Hold, updated every second. Other features include High Repeatability, Auto Zero, Adjustable Alarm Settings, and an Audible Alert which triggers above 35ppm to indicate a dangerous CO concentration. The extremely affordable DCO 1001 has a measuring range of 0-1000 ppm and comes complete with a soft case, a wrist strap, 3 AAA batteries and an instruction manual.