Experimental study of submicrometer and ultrafine particle penetration and pressure drop for high efficiency filters

The fractional penetration of submicrometer particles through five high-efficiency glass fiber filters, one composite fiber filter, and two membrane filters was measured for particles of 0.004–0.42-μm diameter at filter face velocities ranging from 0.5 to 20 cm/s. The glass fiber filters all had approximately the same thickness and weight per unit area, and were rated 93% to 99.999% efficient using the conventional 0.3-μm dioctyl phthalate (DOP) test. The challenge aerosols were electrically classified monodisperse DOP in the diameter range of 0.032–0.42 μm, and polydisperse silver condensation aerosols having diameters of ∼ 0.004–0.01 μm. Aerosol penetration through these media was found to be generally consistent with current theory for collection by diffusion and interception over the particle size and velocity range studied. Using a filter figure of merit calculated for penetration by 0.1- and 0.3-μm particles to facilitate comparison, all of the filters except one tetrafluoroethylene membrane filter (which was slightly better) had about the same performance.