Depending on what you intent to measure, however, l can suggest the USB Monitors which are quite good having used them before.

You can check this website for further information 

http://berkeleyair.com/services/ucb-particle-and-temperature-sensor-ucb-pats/

Dr Akintan,

Thanks for the advice. I need to perform chemical speciation of elements on PM after collection. Does this instrument collect PM on specialized filters? How much is it?

Thanks

I will check . I appreciate your support