Bio-aerosol dynamics in buildings
Date of Issue2016
School of Mechanical and Aerospace Engineering
The importance of having clean air is severely underrated. In recent years, studies have shown the severe negative impact of poor quality air on the human body. Constantly breathing in poor air quality can cause negative health effects such as ischaemic heart disease. Thus, the understanding of bioaerosol dynamics can help to negate the harmful effects of bioaerosols on the human body. ACMV (air- conditioning and mechanical ventilation) has been a major engineering means for controlling indoor environmental quality, especially in tropical Singapore. This study investigates whether ACMV system can reduce indoor bioaerosol exposure, compared to natural ventilation. Bioaerosol (bacteria & fungi) samplings followed by incubation and colony counting were conducted in a laboratory building on NTU campus. When the building is running in ACMV mode, the concentration of airborne bacteria indoors is around 200 CFU/m3 vs around 75 CFU/m3 outdoors. The indoor concentration of airborne bacteria is two to three times higher than the outdoors when running in ACMV mode. The concentration of airborne fungi indoors is around 250 CFU/m3 vs about 400 CFU/m3 outdoors. This shows that the concentration of fungi outdoors is roughly two times higher than the indoors when the building is running in ACMV mode. One possible reason for the difference in I/O (indoor to outdoor) ratio is due to the difference in sizes of bioaerosol. Fungal bioaerosols have a diameter of 1 to 100 μm, which is larger than bacteria which has a diameter of 0.5 to 10 μm. Thus, fungi are more easily captured by the filter in the ACMV system. When running in natural ventilation mode, the indoor concentration of airborne bacteria indoors is around 200 CFU/m3 vs around 175 CFU/m3 outdoors. This shows that the concentration of airborne bacteria indoors and outdoors is similar. The concentration of airborne fungi indoors is around 375 CFU/m3 vs about 350 CFU/m3 outdoors. This shows that the concentration of airborne fungi indoors and outdoors is similar. The lack of filter allows airborne bioaerosol to travel freely between the two environments, resulting in similar concentration levels of bioaerosols.
Final Year Project (FYP)
Nanyang Technological University