Series 450 Carbon Monoxide (CO) Monitor detects toxic gas in ambient air. Measures CO levels from 0 to 2,000 parts per million. Sensor maintains reading accuracy of 3 percent with response time of less than 30 secs. Battery-powered unit boasts hands-free operation. Rugged aluminumwithstands harsh environments. To supplement audible alarm, beacon of light flashes in correspondence to level of carbon monoxide concentration. Raised keypad allows fast calibration, readings storage, lighting, and more. Optional accessories include calibration kit with carrying case and aspirator kit for obtaining samples in hard-to-reach locations.