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PENETRATION OF AMBIENT FINE PARTICLES INTO THE INDOOR ENVIRONMENT
Citation:
Mosley*, R B., D J. Greenwell*, L E. Sparks*, Z Guo*, AND W. G. Tucker*. PENETRATION OF AMBIENT FINE PARTICLES INTO THE INDOOR ENVIRONMENT. JOURNAL OF AEROSOL SCIENCE AND TECHNOLOGY 34(1):127-136, (2001).
Description:
Several recent studies have indicated significant health risks associated with exposure to fine particles as measured outdoors. However, much of the exposure is believed to have occurred infdoors. consequently, there is considerable interest in the relationship between indoor and outdoor fine particles. This paper describes some results from a study in which the processes of particle removal from infiltrating air by building envelopes are simulated in a chamber. The chamber consists of two compartments, each having a volume of 19 m3. Particles with aerodynamic diameters in the range of 0.05 to 5 um are generated in one compartment and then transported through simulated leakage paths to the other compartment under the action of applied pressure differentials. The penetration factor for each size particle is determined by simultaneously measuring the concentrations in the two compartments as a function of time. The penetration factor is obtained through a mathematical solution of the mass balance equations. The measured values of penetration are compared to predictions of a mathmematical model describing deposition by the mechanisms of settling and diffusion. At 2 Pa, the largest particles to pass through 0.5 mm slits are about 2.5 um. At 5 Pa, this size increases to about 3.5 um. While at 10 Pa, the largest size becomes about 5 um. Measurements of particle deposition rates in the chamber are also shown.
The paper also discusses some studies of penetration into an unoccupied research house in which most of the usual indoor sources of particles are absent, and in which the rate of entry of outdoor particles can be controlled largely by applied pressure differentials. Mathematical expressions are developed to compute the characteristic time of response of a building to a change in its environment such as a change in particle concentration or a sudden change in pressurization. Equations are also presented to compute the particle penetration from measured responses of indoor concentration to either a pressurization system or air cleaners.