This paper discusses the measurement of air infiltration rates and reports on measurements relating indoor and outdoor aerosol size distributions in the 0.01 to 1 µm size range. Measurements of air exchange rates with both the induced pressure and tracer gas techniques were performed. It is shown that airflow rates through a blower door duct can be measured to within 5% by making a simple measurement of static pressure drop between air upstream of the duct and a point within the duct. This eliminates the need for fan calibration, which is frequently done for such measurements. Also, simultaneous measurements of air exchange rates with the induced pressure and tracer gas techniques were done in two homes, and the two methods were found to agree to within estimated experimental uncertainties. Finally, indoor and outdoor aerosol size distributions were measured and compared in one home; air infiltration rates were also measured simultaneously by the tracer gas technique. It was found that for particles in the 0.01 to 1.0 µm range, the ratio of indoor to outdoor concentrations was typically between 0.2 and 0 .4 and did not vary systematically with particle size.