What is Aerosol impaction?

Aerosol Impaction is the process in which particles are removed from an air stream by forcing the gases to make a sharp bend. Particles above a certain size possess so much momentum that they can not follow the air stream and strike a collection surface which is available for later analysis of mass and composition. Removal of particles from an air-stream by impaction followed by mass and composition analysis has always been a different approach as to filter sampling, yet has been little utilized for routine analysis because of lack of suitable analytical methods.