Reliable and Quick Carbon Monoxide Detection Carbon monoxide (CO) is a silent killer, making it crucial to perform CO checks during the servicing or installation of gas heating systems or boilers. The compact Testo 317-3 CO Monitor provides a quick and reliable way to test the surrounding air for CO, ensuring safety and proper functioning of heating systems. Key Features Quick Detection: Measures CO concentration in the surrounding air within seconds. Visual and Audible Alarms: Triggers alarms when CO thresholds are crossed, with adjustable settings for customized alerts. Easy-to-Read Display: Presents CO readings clearly for immediate assessment. Portable Design