High air flow, low pressure drop, bio-aerosol collector using a multi-slit virtual impactor

A bio-aerosol collector was developed comprising a low pressure drop, multi-slit virtual impactor, a wetted wall cyclone collector from Research International (RI), and associated plumbing and blowers. The collector is portable, samples air at 1220 L/min, provides 3-8 mL liquid sample, and has 70 W power consumption. The RI collector was selected for this unit following an evaluation of leading commercial aerosol collectors. The compact, multi-slit virtual impactor has an area of 334cm2 and a pressure drop of 0.2 kPa at an inlet flow of 1220 L/min. The virtual impactor reported here concentrates the aerosols by a factor of four when the major to minor flow is adjusted to 4:1 ratio, but it has been field operated at a ratio of 8:1 when sampling at 2300 L/min. A preliminary evaluation of the RI-Lawrence Livermore National Laboratory collector was conducted to verify the unit has low pressure drop and can collect aerosols greater than 2μm. A more detailed evaluation is needed to fully characterize the collector. This bio-aerosol collector has been incorporated in autonomous pathogen detection systems.