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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 (CO 2 ), carbon monoxide (CO), respirable suspended particulates (RSP), nitrogen dioxide (NO 2 ), ozone (O 3 ), 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 O 3 . 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.

Continuous sampling has been widely adopted for assessing indoor pollutant level. It is believed that the longer the measurement time, the higher the accuracy and improved error rate of the measured average pollutant concentration can be achieved. This study proposes an alternative sampling scheme in which the average pollutant concentration is obtained from two short sampling periods in two sampling sessions when a building was occupied. Two indoor pollutant concentration databases for a 1-year continuous measurement of carbon dioxide (CO2) and radon concentration in a typical openplan office building in Hong Kong were used to investigate the probable errors of the proposed scheme regarding the sampling period. The results showed that these errors deviated from a long-term average value and correlated with the required measurement time. At certain confidence levels, the potential reductions in measurement time of the proposed sampling scheme would be up to 30% and 50% for CO2 and radon, respectively, as compared with an 8-h continuous one.

Indoor airborne bacteria and fungi levels can be selected as indicators of a healthy indoor environment. This study investigated the relationships between the airborne bacteria levels, fungi levels, and thermal environmental parameters, i.e., air temperature and relative humidity, in some offices with a Mechanical Ventilation and Air-Conditioning (MVAC) system operating. A total of 101 samples were collected from two typical Hong Kong air-conditioned office premises. There was evidence that the operation of the MVAC system would have significant influence on both of the indoor airborne bacteria and fungi levels. The results showed that no significant difference in airborne bacteria and fungi levels was observed between offices having similar thermal environments ( p > 0.05). However, significantly higher airborne bacteria and fungi levels were found in the same office during non-office hours when the air-conditioning system was shut down ( p<0.03). It was also reported that the airborne bacteria and fungi levels would be correlated with the thermal environmental parameters in some offices ( p<0.0001).