Indoor air quality at nine shopping malls in Hong Kong

doi:10.1016/S0048-9697(00)00833-0

Science of The Total Environment

Volume 273, Issues 1–3, 12 June 2001, Pages 27-40

https://doi.org/10.1016/S0048-9697(00)00833-0 Get rights and content

Abstract

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 CO₂ levels above the 1000 ppm of the ASHRAE standard on both weekdays and weekends. Also, they had average weekday PM₁₀ concentrations that exceeded the Hong Kong Indoor Air Quality Objective (HKIAQO). The highest indoor PM₁₀ level at a mall was 380 μg/m³. Of the malls surveyed, 30% had indoor airborne bacteria levels above 1000 cfu/m³ set by the HKIAQO. The elevated indoor CO₂ and bacteria levels could result from high occupancy combined with insufficient ventilation. The increased PM₁₀ levels 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 PM₁₀ indoor levels. In addition, the extensive use of cooking stoves without adequate ventilation inside food courts could increase indoor CO₂, CO and PM₁₀ levels.

Introduction

Hong Kong is one of the most popular shopping paradises in the world (Heung and Qu, 1998, Choi et al., 1999). Many tourists are attracted to spend their time in shopping malls during their visit to Hong Kong (Heung and Qu, 1998). Besides tourists, local people like to go to shopping malls for entertainment. Therefore, healthy indoor air quality inside a shopping mall is very important to local people and international tourists. Undoubtedly, poor indoor air quality (IAQ) will lower the perceived comfort of air quality in a shopping mall. Increased indoor CO₂ levels in excess of 1000 ppm are closely related to occupant complaints of sick-building symptoms including drowsiness, eye, nose and respiratory irritation (Molhave, 1987, Molhave et al., 1999, Liao et al., 1991). As the Hong Kong government has recognized the potential health risk and problems related to indoor air pollution which occurs in office premises and public buildings, it is striving to investigate and manage the IAQ of various indoor environments (Environmental Protection Department, 1999). A shopping mall is regarded as a type of public building in Hong Kong. Unfortunately, there are few studies that focused on the air quality in shopping malls in particular, in Hong Kong.

Hong Kong is one of the most densely populated cities in the world (Lee, 1997). According to the data given by the Hong Kong Census and Statistics Department, approximately 1000 km² of the land in Hong Kong accommodated more than 6.98 million people at the end of 1999 (Census and Statistics Department, 1999). Also the territory has approximately 500 000 registered vehicles travelling on roads (The Annual Traffic Census, 1998). Hence, there is high population and vehicle density over the territory. Many Hong Kong shopping arcades are located on lower floors or inside basements of high rise commercial buildings that are situated in heavy traffic environments. High traffic densities and abnormal meteorological factors adversely influence the ambient air quality of Hong Kong. Lam et al. (1999) identified that nitrogen dioxide and suspended particulates are the most common and serious air pollutants in many traffic areas in Hong Kong. As fresh air supplied to the shopping malls comes from outdoors, the IAQ of the malls will be closely associated with the outdoor air that is often contaminated by automobile exhausts.

In addition to the air infiltration from outdoor air pollutants, there are several potential indoor sources that can generate air pollutants inside the shopping malls. In order to meet different needs of customers, shopping malls usually offer dining and entertainment facilities, such as department stores, supermarkets, food courts, cinemas and ice-skating rinks, in addition to boutiques. As there are numerous potential indoor sources of air pollutants, the investigation of indoor air pollutants at shopping malls becomes more complex. For instance, elevated levels of CO in ice skating rinks had been observed (Spendler et al., 1978, Brauer et al., 1993, Lee et al., 1994). Exhausted gases released from ice-resurfacing equipment with combustion engines could result in significant quantities of indoor air pollutants if inadequate ventilation occurs in an ice-skating rink (Yoon et al., 1996). Some indoor activities such as cooking and smoking inside the catering and shopping zones of a shopping mall can increase indoor CO and PM₁₀ levels. The use of gas stoves for food cooking is one indoor source of CO (Gold, 1992). Indoor particulate level is closely dependent on the type of cooking fuel used. Traynor et al. (1986) found that indoor concentrations of respirable suspended particulate were significantly elevated at homes during the use of wood-burning stoves. Cigarette smoking could give rise to indoor air pollutants such as CO and PM₁₀ (Sterling, 1991). In order to protect the health of general public and maintain their shopping and dining pleasures, the IAQ should be taken into consideration during the design and operational processes of shopping malls. The objectives of this study were to characterize the IAQ at nine selected Hong Kong shopping malls in Hong Kong and compare the results of this study with health-related IAQ objectives currently required in Hong Kong. Various IAQ sources at shopping malls were also identified in this study.

Section snippets

Field study

As shown in Fig. 1, the nine shopping malls selected are located in different geographical areas of Hong Kong. These monitoring sites were located in major commercial and residential districts where population and vehicle densities are relatively high in Hong Kong. Four shopping malls (SM1, SM2, SM4 and SM7) are located in Kowloon. Three shopping malls (SM5, SM8 and SM9) are situated in Hong Kong Island and two malls (SM3 and SM6) are located in the New Territories. Six of them (SM1, SM3, SM5,

Results and discussion

Fig. 3, Fig. 4 show the indoor and outdoor average concentrations of CO₂, CO, THC, HCHO and PM₁₀ at nine shopping malls on both weekdays and weekends. Outdoor and IAQ Objectives (Pang, 1994) currently recommended in Hong Kong are shown in Table 4. CO₂ concentration is widely used as an indicator of ventilation effectiveness in an enclosed space (ASHRAE, 1989). The average CO₂ levels at the shopping malls ranged from 500 to 2300 ppm. Fig. 3, Fig. 4 illustrate four of the nine malls (SM2, SM3,

Conclusion

The average indoor CO₂ and airborne bacteria levels recorded at more than half of the shopping malls surveyed exceeded the HKIAQO standard. This study found that many shopping malls had higher indoor CO₂ and bacteria levels on weekend evenings than on weekday evenings. The highest CO₂ and bacteria levels were as high as 2300 ppm and 1800 cfu/m³, respectively. The elevated indoor concentrations were due to overcrowded shopping spaces, and high occupancy without sufficient ventilation. The indoor

Acknowledgements

The study is supported by the Research Grant (V749) of the Hong Kong Polytechnic University. The authors would like to thank Mr W.F. Tam for technical assistance and Miss M. Chang, and Mr S.S. Cheung for assistance in sampling at various shopping malls.

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Indoor air quality at nine shopping malls in Hong Kong

Abstract

Introduction

Section snippets

Field study

Results and discussion

Conclusion

Acknowledgements

Tourism Manage

Clin Chest Med

Tourism Manage

Atmos Environ

Environ Int

Environ Int

Environ Int

Standard 62-1989. Ventilation for acceptable indoor air quality

Characterization of air quality problems in five Finnish indoor ice arenas

J Air Waste Manage Assoc

Air pollutant exposures inside the ice hockey rinks: exposure assessment and reduction strategies

Press release — end year population for 1999

Literature review on CO2-based demand controlled ventilation

ASHRAE Trans.

Literature review on CO₂-based demand controlled ventilation