Measure ambient air CO with any DMM. No Bulk, easily carry one on your belt or tool box. Easy to use with any DMM or clamp-on meter with a minimum 3-1/2 digit LCD, 2 or 4 Volt DC range and 10M or greater input impedance. A771 generates 1mV per 1ppm of CO. Detects CO levels from 0-1999 ppm, with resolution as low as 0.1ppm and +/-5 percent of reading accuracy. Low battery and power indication. Calibrate in the field. Complete with belt pouch, A771P. Use as personal CO alarm. Conduct tests of CO levels in room air to meet ASHRAE and OSHA Standards. Confirm proper operation of alarming CO detectors in households. Check for proper installation of ventless gas fireplaces, furnaces, and other combustion devices. Use as a personal alarm preset at 30 CO. Co sensor: 24 month warranty. Range: 0 - 1999 ppm with 3.5 digit DMM display. Alarms: Visual/audible. Alarm set range: 0 to 200 ppm. Response time: 90 Percent of reading in 30 seconds. Operation temperature: -10 to 50 degree or -50 to 122 degree F. Relative humidity: 5 to 95 percent RH. Accuracy: +/-5 ppm or 5 percent of reading whichever is greater. 1ppm resolution. 1mVDC / 1ppm CO into 10M Ohm impedance output. Measures 2" width by 6-1/2" height by 1-1/4" depth. Battery: 9V Alkaline. Battery life: 500 hours. CE Approved. 3 Years limited warranty. 2 Year sensor warranty.