Printed in Great Britain Pergamon Prds pic British Occupational Hygiene Society REVIEW MODERN CONCEPTS OF AIR FILTRATION APPLIED TO DUST RESPIRATORS

Abstract—The current state of development of those aspects of air filtration particularly relevant to dust respirators is reviewed. Models and theories of airflow are described, and this description is followed by an account of the various mechanisms of particle capture by mechanical means and by electric forces. Electrically charged materials that are, or could be, used in respirator filters are described and classified according to the methods by which they become charged. Ways of measuring the charge level are summarized, and the stability of electric charge on filters is discussed with respect to storage, exposure to harsh environmental conditions and use. Measurements of filtration efficiency using monodisperse laboratory aerosols, industrial aerosols and standard aerosols are put into their various perspectives. The review ends with a brief account of the place of coarse mechanical filters in industrial hygiene