Experimental studies of the effect of rough surfaces and air speed on aerosol deposition in a test chamber

Understanding the fate of particles indoors is important for human health assessment because deposited particles, unless resuspended, cannot be inhaled. To complement studies in real buildings, where control of variables is often difficult, an experimental test chamber facility (8 m³) was designed to study particle deposition under well-stirred conditions using monodisperse tracer aerosol particles in the range of 0.7 to 5.4 μm. The use of neutron-activatable tracers facilitated simultaneous surface sampling and aerosol concentration decay measurements. Aerosol deposition on both smooth surfaces and regular arrays of three-dimensional roughness elements under 3 different airflow speeds was investigated in the test chamber. It was expected that the texture of the chamber surface would significantly influence particle deposition, but some counterintuitive results were observed: under the lowest airflow condition and for the smallest particle size, particle deposition onto rough samples was found to be less than on the corresponding smooth surfaces. The ratio of particle deposition on rough surfaces relative to smooth surfaces increased with particle size and magnitude of airflow. For the largest particle size and airflow speed, particle deposition on the rough surfaces exceeded that on the smooth surfaces by a factor of 3.