TPI A771 Carbon Monoxide Monitor features Built-in alarm is preset to 30 ppm. Setting can be set by user. Use with any DMM with minimum 2 1/2 digit LCD, 2 or 4Volt DC range and 10M Ohm or greater input impedance. Detect CO levels from 0-1999 ppm, with resolution as low as 0.1 ppm and ??5 percent of reading accuracy. Soft pouch included.