The Triplett GSM120 Portable Carbon Monoxide (CO) incorporates a stabilized electro-chemical gas-specific (CO) sensor to measure CO from 0 to 1000ppm. The GSM120 can be used to check Carbon Monoxide (CO) levels in chimneys/flues, gas appliances (ovens, ranges, dryers), furnaces, internal combustion engines, portable generators, and all coal/wood/charcoal/oil/kerosene/propane/natural gas burning devices. The GSM120's audible alarm at 35ppm increases beeping until continuous at 200ppm. The GSM120 measuring time mode displays elapsed time from when the meter is powered on and Max Hold records the highest reading. The GSM120 additional features include self calibration in fresh air, manually store/recall 10 readings, backlit LCD display, and auto power off with disable. 1 year warranty.