OBJECTIVE To obtain the decline patterns of bioaerosols with different relative humidities and microbial species in steady-state space.

METHODS Four microorganisms, namely Escherichia coli, Staphylococcus aureus, Bacillus atrophaeus and Serratia marcescens, were selected for the generation of bioaerosols with a vibrating screen generator. The relative humidity was controlled in an environmentally controllable experimental chamber. The bioaerosols were collected with a six-grade Anderson sampler, and the concentration was calculated to obtain the decline rate of bioaerosols at different time points.

RESULTS When the relative humidity was 60%, the concentration decline rates of the four microbial aerosols were all greater than 40% at 15 minutes. The decline rate of S. marcescens aerosol was close to 100%, and by 90 minutes, the decline rates of the other three bioaerosols reached over 90%. The influence of relative humidity on the decline rate of bioaerosols was significant, but the patterns varied. When the relative humidity increased from 40% to 80%, the decline rates of E. coli and S. marcescens aerosols decreased by 32% and 23%, respectively, at 15 minutes, while the decline rate of S. aureus aerosol increased. The decline rate of B. atrophaeus aerosol also decreased with increasing relative humidity, but the decrease tended to slow down after the humidity exceeded 60%.

CONCLUSIONS The concentration of bioaerosols in steady-state space declines significantly over time and is significantly influenced by environmental relative humidity and their own biological characteristics. Different types of bioaerosols are affected by environmental humidity in varying patterns. When conducting research, detection, modeling and other work related to bioaerosols, the influence of environmental relative humidity and the microorganisms themselves on the stability of bioaerosols should be fully considered.