Those involved in property management are under pressure to alleviate the risk of disease spread through buildings, especially via the Heating, ventilating and air-conditioning (HVAC) system. To aid this, the level of indoor bacteria can be used as a referent to identify the performance of the HVAC system. Epistemic assessment of an AC office requires prior knowledge of the probable failure rate of offices in a region, which may be obtained by extensive measurements. This study proposes a statistical model to obtain a rapid estimation of the office probable failure rate over a region, that is, that fraction of offices with an average bacteria level above certain action levels. The model was based on transformation of small sample data to a geometric distribution using two analytical unbiased estimators: the weighted average and corrected sample variance of bacteria levels. These estimators could improve the accuracy of the estimates due to uncertainties of small sample sizes. Model parameters were determined from a dataset of levels in 290 Hong Kong offices (average 703 cfu m— 3 and 95% range 204—2418 cfu m— 3), using Monte Carlo simulations. The model was validated with another district survey of 109 offices in nine major Hong Kong commercial districts (average indoor bacteria level 297 cfu m—3 and 95% range was 69—1266 cfu m—3). The observed office failure rate of each district was compared with the corresponding model estimate and consistent results were found.
Long-term measurement results of indoor air quality (IAQ) over a general community can be used to evaluate the effectiveness of mitigation measures for IAQ improvement of premises. However, this approach requires considerable measurement efforts and thus the complete data sets are not available in many circumstances. This study proposes an epistemic approach in estimating the probable influences of an IAQ policy for Hong Kong offices, using the regional IAQ measurement databases results of IAQ in offices were collected and were used to quantify the IAQ improvement for Hong Kong offices. It is noted that IAQ dissatisfaction due to air pollutants predominated by indoor emissions of volatile organic compounds (VOCs) might need additional attentions for an effective IAQ improvement programme. Practical application: This study provides updated information on the forecasts of IAQ in air-conditioned offices of Hong Kong due to the influence of the IAQ policy implemented in 1997-1999. It is a useful source of reference for policymakers and decision makers in evaluating an indoor air pollution control policy for air-conditioned offices.
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