Abstract: Apparatus is disclosed for rapidly collecting aerosols containing solid particles and micro organisms, such as viruses and bacteria, from relatively large volumes of air and concentrating these particulates as samples in water. This apparatus operates under conditions conducive to preserving the integrity and viability of the collected micro organisms. Ambient air containing aerosols drawn into and through the collector's interior by an air mover, is mixed with very warm air saturated with moisture and then with cold air, to cause the resulting vapor mixture to become supersaturated. This supersaturated water vapor rapidly condenses onto the incoming aerosol particles to form droplets with particles at their centers. The airstream carrying these droplets enters a cloud of air ions produced by a corona generator or, alternately, by a radioactive source emitting alpha particles.