A 10-μm Two-Stage Inlet for Sampling Indoor Aerosols

Abstract

An inlet for sampling indoor aerosols has been developed. It has a outpoint of 10 ± 0.5 μm aerodynamic diameter and a penetration curve slope of 1.51. The unit is designed to operate at a flow rate of 240 L/min. Tests in a wind tunnel at speeds Of 1, 2 and 4 km/h showed there to be no substantial variation of cutpoint with wind speed. In tests with 9.7-μm particles at wind speed of 2 km/h, the sampler orientation was varied to simulate air stream angles of attack. For the sampler axis at −10°, 0° and +10° from the vertical direction, the range of penetration values was only from 51.2 and 53.9%. Other tests, in which the flow rate was varied from 216 to 264 L/min, showed the performance of the inlet was not appreciably affected. Re-entrainment or bounce of solid particles is not of consequence. The difference in penetration of 20-μm aerodynamic diameter glass beads and liquid aerosol is less than 2% at 2 km/h. Collection filters were examined for uniformity of deposits associated with the sampling of 10.2-μm particles. The pooled standard deviation of three test filters with 10 subsamples from each test filter was only 1.8% of the mean of the deposits.