An experimental study on short-time particle resuspension from inner surfaces of straight ventilation ducts

In this work, effects of particle size, air speed, and time factor on the short-term resuspension of micron and submicron particles in straight ventilation ducts were experimentally studied with a focus on the particles airborne from the inner surface of ventilation ducts. The experimental method was designed to monitor continuously the particle resuspension rate owing to lift-off. The duct systems were made of typical commercial materials. The particles tested were in eleven size groups in the range of 0.4–10 μm. The experiments were conducted at six air speeds: 3.8, 5.1, 6.3, 7.1, 8.0, and 8.8 m/s and each test lasted for 180 s. The measured particle resuspension rates increased with the increases of the air speed to a certain values, ranging from 9.2 × 10−11 s−1 to 3.7 × 10−9 s−1 corresponding to the particle size of 0.4–10 μm, while the measured particle resuspension rate was smaller than previous reported results. The measurements also showed that particle resuspension rates were independent of time during the first 60 s and then decreased sharply. The experiments suggest that more particles slide and roll off rather than being lifted into the air flow and that higher air speed may reduce the amount of particles lifted into air flow as more of the particles may become airborne due to sliding and rolling off.