Extech co210 air meter and data logger extech co210 the extech co210 air meter and data logger checks for carbon dioxide co sub 2 sub concentrations using a maintenance free non dispersive infrared ndir co sub 2 sub sensor this neat desktop unit displays indoor air quality in ppm with good 380 to 420ppm normal lt 1000ppm and poor gt 1000ppm indication if required poor air quality will trigger a visible and audible co sub 2 sub warning alarm with a relay output to activat