you can compare the IQAir models here, the 3rd filter is activated carbon and some other neutralizing chemicals for gaseous pollutant and odour control
http://www.iqair.com/uk/pdf/iqair-hp-series.pdf
don't worry, they will deliver the very same result on a 500.000 p/l day ...
and if you really want to buy a L aser particle counter you will have to fork out at least a few thousand US$ ... thats just what they cost:
Handheld Particle Counter: Experts Review Handheld Particle Counters