SM207 Portable Formaldehyde (CH2O) Gas Detector Meter Indoor Air Quality sensor Tester

The best I can say for this unit is that it is not very sensitive. After calibrating it in outdoor air as instructed, it read 0.00 ppm in a location with a concentration of 0.046 ppm formaldehyde concentration as measured with industry standard SKC UMEX-100 badge samplers analyzed by AIHA accredited laboratory.8/10/2015: I've lowered this to one star. It started indicating formaldehyde concentrations of 1-2 ppm in the location mentioned above. I took it out to the garage, it indicated 8 ppm there! (Note: most people can smell concentrations greater than 0.5 ppm). After several recalibrations in outside air it went back to reading 0.00 ppm! Clearly unreliable instrument, don't waste your money on this.

Buy this over a one time rapid air test... a one time test is a wastes of money.