It seems pretty accurate. The South Coast Air Quality Management District tested a bunch of consumer devices against a $30,000 professional device. I was deciding between the IQAir and Laser Egg 2+, which both did well according to their tests http://www.aqmd.gov/aq-spec/evaluations/field. I got the Laser Egg 2+ the other day. It's really enlightening to see how it spikes when we cook dinner or lunch on the gas stove.
Pretty accurate, there was an air quality report which compared about 3-4 samples of them with commercial air monitors - the lab found them adequate with some but not massive sample variance. They were the best of the consumer models tested.
Can’t seem to find the report but to be honest I stumbled on it while searching for PDFs on the subject a year or two back. (I own no stock nor have any affiliation with IQAir - just a satisfied customer - high price not withstanding).