Abstract: In air sampling system and a calibration system therefor are disclosed for use therewith in order to provide air sampling for, for example, environmental tobacco smoke aerosol in a portable personal air sampling system. The air sampling system utilizes a sampler head having a manifold block which allows for the collection of air for studying both the particulate and vapor phases of environmental tobacco smoke aerosol using only a single pump. An air flow calibrating system is utilized to measure and calibrate the air flowing through the two collection devices used in connection with the manifold block in which the air flow through the two sampling assemblies is simultaneously read out.