The protective role of personalized ventilation (PV) against plausible airborne transmissible disease was investigated using cough droplets released from a 'coughing machine' simulating the human cough at different distances (1, 1.75 and 3 m) from the PV user. Particle image velocimetry was used to characterize and visualize the interaction between the coughgenerated multiphase flow and PV-induced flow in the inhalation zone of the thermal breathing manikin. A dose-response model for unsteady imperfectly mixed environment was used to estimate the reduction in infection risk of two common diseases that can be transmitted by airborne mode. PV was able to both reduce the peak aerosol concentration levels and shorten the exposure time at all the examined injection distances. PV could reduce the infection risks of two diseases, influenza A and tuberculosis, by between 27 and 65 per cent. The protection offered by PV is less effective at a distance of 1.75 m than the other distances, as shown in the risk assessment results, as the PV-generated flow was blown off by the cough-generated flow for the longest time. Results of this study demonstrate the ability of desktop PV to mitigate the infection risk of airborne transmissible disease.

No abstract

Combustion activities such as cigarette smouldering, incense burning and cooking are important sources of particulate matters (PM) in indoor environments. Vacuum cleaning contributes to the non-combustion-related sources of PMs. In this study, we investigated the rates at which ultrafine particles (UFPs) are emitted from cigarettes, incenses and vacuum cleaners in a small test chamber. UFP emission from cooking was obtained by conducting experiments in a residential kitchen. Particle number concentrations and size distributions from these sources were measured using a scanning mobility particle sizer (SMPS) and the UFP emission rates were then determined using a material balance approach. The mean UFP emission rates of cigarette smouldering and incense burning were found to be 3.36 ± 0.34 and 0.44 ± 0.33 × 1011 particles min−1 in terms of the number emission rate, or 22.78 ± 1.21 and 3.48 ± 2.98 × 1015 nm2 min−1 in terms of the surface area emission rate, respectively. Vacuum cleaner motor operation and cooking showed high variations in UFP emission, in the ranges 0.013–0.066 and 4.70–148.29 × 1011 particles min−1, respectively. A database of emission rates for UFP sources can be compiled, which will be useful in estimating the UFP concentration and subsequent human exposure.