Quick and accurate measurements of ambient CO values with the testo 317-3 The testo 317-3 ambient CO detector is ideal for HVAC contractor who need a reliable tool for precise carbon monoxide detection. The flue gas meter is equipped with an exclusive self check that eliminates the need for zeroing in a fresh air environment. The extremely sensitive sensor is able to function anytime with a range up to 1,999 ppm. Both visual and audible alarms with an adjustable high and low threshold simplify servicing and maintenance of heating systems during inspections of homes and commercial buildings. The compact design of the HVAC servicing instrument in combination with the included belt clip soft case enable a convenient hands-free application. Technical Data: Ambient CO measuring range: 0 to +1999 ppm Ambient CO measurement accuracy: ±3 ppm (0 to +29 ppm/ ±10 % (+30 to +1999 ppm) Operating temperature: 23° to 113 °F / -5 to +45 °C Battery type: 2 AAA batteries Battery life: 150 h (with beeper switched off) Storage temperature: -4° to 113 °F / -20 to +45 °C Delivery Scope: ? testo 317-3 ambient CO stick ? Protective soft case with belt clip ? Hand strap ? Earbuds ? 2 AA batteries ? Instruction manual