with a fluid based collector is characterized by higher detection probability furthermore the limited volumes of liquid greatly reduce the logistics burdens associated with these types of devices the development of the inventive method includes the utilization of the aerosol generator 22 mounted upstream from the impaction surface 26 among a variety of methods and devices configured to generate an external aerosol are for example a standard nebulizer a piezo electric based nebulizing system and or an inkjet style aerosol generator which have been successfully implemented a standard nebulizer 60 uses a pressurized air stream to generate liquid particulates by initially aspirating a liquid out of a reservoir and blows the aspirated liquid against a surface to cause particulates contained in the liquid to shear apart entranced in a carrier fluid generated by a pressurized source the sheared particulates become aerosolized and delivered into the air stream 34 to co aerosolize the particles of interest contained in the air stream 34 the location of the aerosol delivery into the air path 34 can vary for example as shown in fig2 the aerosol 62 entrains the air stream while the latter flows along the narrow cylindrical portion 36 of the focusing mechanism 24 another possible location of the injection is at an input plenum to the impactor 30 alternative locations for the injection are between the air air virtual impactor and the tape impactor 26 or between the stages of.