The retention of large particles (greater than 2mum) in fibrous filters.

A simple method of testing fibrous filters to obtain the grade efficiency curve in the particle size range 2-22 mum is described. Dust collected by the method has been used to measure the retention efficency of model filters and it is shown that there is a maximun in the grade efficency curve. The influence of relative humidity on filter behaviour has been investigated. It is shown that the efficiency of filtration in high particle inertia systems increases with increasing relative humidity. It is considered that the reason for this is an increase in particle-fiber adhesion force.