Review: Activated Carbon Filters in Respiratory Protective Equipment

The review considers first the nature of airflow through granular carbon filters and the relationship between pressure drop and airflow rate. Equilibrium adsorption is then summarized, with particular emphasis on the volume filling of micropores, on which most of the theory of activated carbon performance is based. The dynamics of adsorption is studied, and the analytical solution of the fundamental dynamic adsorption equation is given, leading to the development of various equations used in practice for the description of breakthrough. The most fundamental dynamic parameter, the rate constant for adsorption, is discussed, and the effects of concentration, granule diameter, and air stream velocity are summarized. Extracts of a number of experimental observations with reference to specific adsorbates are given, followed by an account of the adsorption of mixtures of compounds. The effect of relative humidity is discussed. This is followed by an account of non-destructive tests, and the review ends with a summary and an indication of possible fruitful areas for research.