A sampler apparatus is disclosed. The sampler apparatus comprises an impactor assembly comprising a nozzle plate, an impaction plate, and a filter unit. The nozzle plate comprises a plurality of nozzles for channelling an air stream through the sampler apparatus. The impaction plate is adapted to collect particulate matter having size equal to or greater than a threshold size. The filter unit is adapted to collect particulate matter having size less than or equal to the threshold size. The sampler apparatus further comprises a control assembly coupled with the impactor assembly. The control assembly comprises one or more flow control devices to maintain a predetermined air-flow rate of the air stream within the sampler apparatus.