Using an ultraviolet-light induced fluorescence (UV-LIF) technique, we measured number concentrations of total aerosol particulate matter (tPM) and fluorescent biological aerosol particles (bioPM) (1.0-3.0 µm and 3.0-5.0 µm diameter) in an office and outdoors, sampling with 1-min resolution. The air-conditioning and mechanical ventilation (ACMV) system equipped with high-grade filters was effective in controlling both tPM and bioPM indoors. As expected, removal efficiencies were found to be size dependent. One human subject walking on the carpet was found to be a strong contributor to bioPM, resulting in 2-3 times higher concentration than that outdoors. Compared to the times when the room is vacant, the biological proportion of total airborne particles increased by an order of magnitude during the light walking period. Consequently, indoor-to-outdoor ratios depend on the ACMV operating conditions and on human activities. This pilot study provides preliminary data concerning the bioPM levels in an indoor environment equipped with an ACMV system. Ongoing investigations using this approach promise to improve our understanding of the processes that influence indoor bioaerosol levels and the effectiveness of control alternatives.

Absent unvented combustion, in occupied indoor spaces, CO2 concentrations depend primarily on three factors: Outdoor CO2 concentrations, CO2 emission rates from human metabolism, and the outdoor-air ventilation rate. Indoor CO2 levels are generally managed by means of dilution with outdoor air. In this work, we investigate an alternative approach to controlling indoor CO2: Active removal using a solid sorbent. We report parameterizations of chemical kinetics and uptake capacity to soda-lime sorbent across a range of conditions relevant to indoor environments. Reaction rate constants for the interaction of Ca(OH) 2 present in soda-lime and CO2 range from 1.8×10-2 to 1.5×10-1 m2 mol-1 s-1, increasing with higher relative humidity (RH). Uptake capacities range from 0.04 to 0.36 g CO2/g sorbent, also increasing with higher RH. These data facilitate assessment of the technical feasibility of soda-lime scrubbers in buildings as an option for controlling indoor CO2.

Particle filters are important components of HVAC systems. Biomass accumulation on HVAC filters can potentially have adverse effects on building occupants. The research reported in this paper aims to quantitatively describe the content of biomass on HVAC filters from various indoor office environments in Singapore in relation to key governing processes. In this initial phase, filter samples were collected and analysed using DNA-based methods. The collected DNA was directly extracted from the filters and the final concentration was measured with Qubit and qPCR methods. The DNA concentrations were then related to the cumulative indoor occupancy level. The results show good correlations between bacterial DNA and cumulative occupancy. The proportion of total DNA that belongs to fungal and bacterial species decreases as occupancy level increases, probably because of biomass from other sources such as human skin cells.