Influence of ventilation on indoor airborne particulate and radon in residential buildings in Hong Kong

Ventilation is intended to provide fresh air to buildings in order to dilute internally generated pollutants and unwanted odours. In reality, the indoor air may be contaminated by incoming air, which is itself polluted. Traffic emissions, construction site activities, and industrial processes can contaminate the ambient air. The main pollutants are carbon monoxide, nitrogen oxides, volatile organic compounds and particulate dispersed in the atmosphere. As a results of exchanging, these pollutants travel with an air stream through the building shell. Whilst particulate is ubiquitous in the outside air, the penetration of particulate to the indoors can be reduced by reducing ventilation.; In Hong Kong, key building materials contain uranium and thorium series elements, which are radon liberators. Unfortunately, indoor radon may accumulate to levels of concern if the premises are not provided with sufficient ventilation. The dilemma is acute when the outdoor air is highly polluted, and the indoor radon emission rate is significant.; In collaboration with the Hong Kong Environmental Protection Department (HKEPD) a systematic and territory wide survey of indoor particulate was conducted in residential premises in Hong Kong between September 1997 and January 1998. The survey was to determine indoor particulate levels by measurement. Fifty residential sites were covered in the survey.; To understand the mechanisms of outdoor particulate penetration through the building shell, a detailed measurement on indoor/outdoor ratio of particulate, together with ventilation measurements, were carried out in five residential premises in Hong Kong.; Building materials are likely to be the main source of indoor radon in Hong Kong's high-rise residential buildings. Understanding the strength of radon emanation rate of building materials can help in the application of measures to mitigate indoor radon.; Besides radon emanation investigations, a small-scale radon survey in residential premises was also carried out. Thirteen premises were covered in the measurements. The survey found that mean indoor radon level in residential premises was below the HKEPD air quality guidelines of 200 Bq m−3 . The relation between indoor/outdoor radon ratio and ventilation was also obtained from the measurements. The results showed that indoor/outdoor radon ratio tended to one when the air change rate of the premises was greater than 4 hr−1, and indoor/outdoor radon levels were not significantly different beyond this value.; Based on the phenomena of pollutant transmission, a ventilation strategy is suggested to ease the dilemma between outdoor particulate penetration and indoor radon mitigation for residences. An air change rate of 0.5 to 0.7 hr −1 was found to achieve suitable background ventilation to mitigate radon. The suggestion is important for ventilation design criteria to ensure levels of these two significant indoor pollutants are as low as practical circumstance permit. (Abstract shortened by UMI.)...