The Amprobe CM100 is a compact size carbon monoxide (CO) meter for measuring and displaying the presence of carbon monoxide. The CM100 displays the CO level on its dual digital display and allows users to select the level from 25 to 200 ppm at which the alarm is triggered. You can set the meter’s alarm to alert when a CO level goes beyond a predetermined safety level. The CM100 User's manual has a chart of published safety levels for CO.