When filtration is used in an air conditioning system further removal of particles occurs on the air mover, the associated air conditioning equipment, the duct walls, and surfaces within the conditioned space. This removal, commonly called passive removal, will affect the particle distribution of the active filtration element.

To determine this effect, active and passive removal mechanisms were investigated in an environmental chamber. The active methods included filtration and collection on wet surfaces (i.e., dehumidification). The passive methods investigated were removal of particles by the chamber surfaces (e.g., diffusional deposition, settling, and coagulation) and system (fan) removal. During these tests measurements of particle size distributions were made for the particle diameter range of 0.01 to 1.0 microns.

A comparison between measured results for both active and passive removal mechanisms shows variations in the particle size distributions with the change in distribution depending on the removal method considered.

Key Words: Chamber, Particle Distribution, Humidification, Filtration, Removal, Tobacco Smoke

Units: SI