Indoor air quality at nine shopping malls in Hong Kong

Hong Kong is one of the most attractive shopping paradises in the world. Many local people and international tourists favor to spend their time in shopping malls in Hong Kong. Good indoor air quality is, therefore, very essential to shoppers. In order to characterize the indoor air quality in shopping malls, nine shopping malls in Hong Kong were selected for this study. The indoor air pollutants included carbon dioxide (CO2), carbon monoxide (CO), total hydrocarbons (THC), formaldehyde (HCHO), respirable particulate matter (PM10) and total bacteria count (TBC). More than 40% of the shopping malls had 1-h average CO2levels above the 1000 ppm of the ASHRAE standard on both weekdays and weekends. Also, they had average weekday PM10concentrations that exceeded the Hong Kong Indoor Air Quality Objective (HKIAQO). The highest indoor PM10level at a mall was 380 μg/m3. Of the malls surveyed, 30% had indoor airborne bacteria levels above 1000 cfu/m3set by the HKIAQO. The elevated indoor CO2and bacteria levels could result from high occupancy combined with insufficient ventilation. The increased PM10levels could be probably attributed to illegal smoking inside these establishments. In comparison, the shopping malls that contained internal public transport drop-off areas, where vehicles were parked with idling engines and had major entry doors close to heavy traffic roads had higher CO and PM10indoor levels. In addition, the extensive use of cooking stoves without adequate ventilation inside food courts could increase indoor CO2, CO and PM10levels.