Particle size distributions for an office aerosol

Abstract

As attention has focused on indoor air quality, it has become important to obtain basic information on the effects of heating, ventilating, and air-conditioning system operating parameters on office aerosols. In addition, it is important to know the particle size distributions (PSDs) in a typical office environment in order to address mitigation strategies. Therefore, this study was undertaken to evaluate the effect of percent outdoor air supplied and occupation level on the PSDs and mass concentrations for a typical office building. The outdoor, return, and supply air streams, as well as hallway air, were sampled using measuring equipment covering particle diameters from below 0.1 to above 3.5 μm. The mass concentrations, when the building was occupled, increased by a factor of approximately 2 when return air was recycled over ventilating with maximum outdoor air. The concentrations when unoccupied were at least as low using minimum outdoor air as those when occupied using maximum outdoor air. As expected, the outdoor air was cleaner than the other streams. The next lowest concentrations were obtained for supply air, then return air, with hallway air showing the highest concentrations. The normalized number distributions were found to have a single mode consistently near 0.13 μm; the volumetric distributions show a peak at 0.3 μm. The influence of the damper setting and occupancy level shows up only in the magnitude of the peaks. The distributions found in the hall and for the air streams showed the same general shapes, but the differences in instrumentation preclude other conclusions. © 1990 Elsevier Science Publishing Co., Inc.