UC Berkeley

Particle penetration into buildings influences human exposure to particles of ambient origin. In this study, we present the results of laboratory experiments measuring particle penetration through surrogates of cracks in building envelopes. Rectangular slots were prepared, with crack heights of 0.25 and 1 mm and flow-path lengths of 4-10 cm, using common building materials: aluminum, brick, concrete, plywood, redwood lumber, pine lumber, and strand board. Air was drawn through a slot from a well-mixed chamber by applying a pressure difference (Delta P) of 4 or 10 Pa. Nonvolatile, electrically neutralized particles were generated and introduced into the chamber. The particle penetration factor was determined, for particle sizes 0.02-7 mum, as the ratio of the particle concentration downstream of the slot to that in the chamber. Particle size and crack height were the two main factors that governed fractional particle penetration. Consistent with prior modeling results, the penetration factor was nearly unity for particles of diameter 0.1-1.0 mum at greater than or equal to0.25 mm crack height and DeltaP of greater than or equal to 4 Pa. Particle penetration diminished for larger and smaller particles and for cracks with significant surface roughness and irregular geometry.