Feasibility Study of an Express Assessment Protocol for the Indoor Air Quality of Air-conditioned Offices

It is costly to sample all major toxic pollutants in community air. Sampling should be conducted based on an assessment strategy and monitoring planning. Assessment methods that rely on monitoring some representative pollutants have been proposed variously at different times. In Hong Kong, the Environmental Protection Department (HKEPD) launched an Indoor Air Quality (IAQ) certification scheme to grade the IAQ in workplaces as “Excellent” or “Good” by measuring the levels of 12 indoor environmental parameters, i.e. carbon dioxide (CO2), carbon monoxide (CO), respirable suspended particulates (RSP), nitrogen dioxide (NO2), ozone (O3), formaldehyde (HCHO), total volatile organic compounds (TVOC), radon (Rn), airborne bacteria count (ABC), temperature (T), relative humidity (RH) and air velocity (V). The present study proposes an Express Assessment Protocol (EAP) to quantify IAQ problems by assessing the “dominant” contributors to unacceptable IAQ prior to any detailed assessment for benchmark purposes. To aid this, a comprehensive measurement of the 12 stated indoor environmental parameters was performed in some Hong Kong offices. The results were used to identify the dominant contributors and assess the performance of the proposed protocol in identifying the associated IAQ problems in an office environment. Comparing the results with the parameter measurements in the certification scheme they showed that for the “Excellent” IAQ level, 96% (94 to 98% for 95% confidence interval (CI)) of the “unacceptable” offices (414 samples) could be identified from the measurements of TVOC, RSP and HCHO; while those that achieved the “Good” level, 93% (90 to 97% for 95% CI) of them (201 samples) could be identified from the measurements of TVOC, ABC, RH, HCHO and O3. The EAP would be a useful tool for policymakers, building owners and professionals to quantify IAQ problems in offices and to make improved decisions based on resources and manpower management for efficient mitigation actions.

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