Indoor air quality at shopping malls in Kota Kinabalu, Sabah (particulate matter and ozone)


Background: Indoor air quality (IAQ) in shopping malls is an interesting case of study since a shopping mall is a public place where people favor to spend their time. This study was conducted to investigate the IAQ of shopping malls in Kota Kinabalu, Sabah, whereby three shopping malls were selected as investigation sites. Methods: The parameters being studied include particulate matter (PM0.3-∞, PM0.5-∞, PM2-∞ and PM5-∞) and ozone. Indoor and outdoor air measurements were performed in the three shopping malls on weekdays and weekends to determine the I/O ratios. Results: In this study, overall average indoor PM concentrations on weekends were higher than weekdays, reaching maxima average concentrations of 421.44 ± 102.96 µg/m3 for PM0.3-∞, 41.75 ± 15.54 µg/m3 for PM0.5-∞, 1.30 ± 0.41 µg/m3 for PM2-∞, and 0.21 ± 0.09 µg/m3 for PM5-∞. Correlation between indoor and outdoor PM concentrations mostly showed poor relationship in the three shopping malls, showing that indoor sources such as re-suspension phenomena due to occupant’s activities were clearly the main contributors to indoor PM concentrations. Poor ventilation system also affected IAQ by increasing the PM accumulation. However, I/O ratios were often less than 1.0, indicating that PM in indoor air arises predominantly from outdoor air transported to indoors. Average indoor ozone concentration at all the shopping malls was measured to be below the 0.05 ppm of ICOP-IAQ 2010. Conclusion: The overall assessment of IAQ in the three shopping malls showed that SM2 has a better IAQ compared to SM1 and SM3.

Keywords: Indoor air quality (IAQ), particulate matter, ozone, relative humidity, indoor temperature

How to cite this article:
Payus C, Chai C. Indoor air quality at shopping malls in Kota Kinabalu, Sabah (particulate matter and ozone). Ann Trop Med Public Health 2017;10:31-5
How to cite this URL:
Payus C, Chai C. Indoor air quality at shopping malls in Kota Kinabalu, Sabah (particulate matter and ozone). Ann Trop Med Public Health [serial online] 2017 [cited 2017 Jul 15];10:31-5. Available from:

In the last several years, indoor air quality (IAQ) has been attracting increasing amounts of public attention from all over the world.[1] The U.S. Environment Protection Agency has even ranked indoor air pollution among the top five environmental risks to public health.[2] This is because scientists found out that the indoor levels of concentrations of some pollutants are higher than their levels outdoor and people spend 80–90% of their time indoor such as office, workplace, school, and house.[3],[4] For this reason, some experts believe that more people may suffer from the effects of indoor air pollution than from outdoor air pollution, where indoor pollutants may pose a greater health threat.[2],[5]

People may be exposed to various indoor environments, especially in public places like shopping malls. In Malaysia, the development of shopping malls has been evolving since early 1970s.[6] Till the year 2012, it is reported that there were about 320 shopping malls operating in the country, with an estimation of 50–60 new shopping malls expected to be developed in future.[7]A shopping mall is defined as a large building with a lot of shops, restaurant, and sometimes a cinema. It includes a group of retail under one covered walkway in order to establish business activity by encouraging pedestrian flow through.[6],[8] On a daily basis, people enjoy spending sometime in a shopping mall. According to the Malaysian Association of Shopping and High-rise Complex Management, one in five Malaysians visited a shopping mall on a weekend.[7] Furthermore, shopping malls are also often packed with customers during holidays. Indoor air pollution in the malls may add to workers’ and customers’ exposure to air toxics.[1]Therefore, healthy IAQ inside a shopping mall is absolutely essential for good health and comfort.[9]

Materials and Methods

The study was conducted at three shopping malls in Kota Kinabalu, the capital city of Sabah. The three shopping malls are stated as Shopping Mall1 (SM1), Shopping Mall2 (SM2), and Shopping Mall3 (SM3) in respect of confidentiality of the shopping malls’ name. SM1 is Sabah’s largest shopping mall and is located about 7 km away from the city center. SM2 and SM3 are centrally located within downtown of Kota Kinabalu. All the three shopping malls are detached building and located in major commercial and residential districts where population and vehicle densities are relatively high. The major entrances of the selected shopping malls are located at the street level and are left opened onto nearby traffic roads, providing direct access to both shoppers and outdoor air. All the buildings are multi-storied and ventilated with central air conditioning systems. The three shopping malls are the center of attraction for locals and international tourists, where there are even more visitors on weekends and public holidays.

The air pollutants investigated in this study include particulate matter (PM0.3-∞, PM0.5-∞, PM2-∞, and PM5-∞) and ozone (O3). Research objectives required data collection and data analysis of the two parameters inside shopping malls. PM samples were collected with the help of Met One Hand Held Particle Counter (model GT-321), which measured PM at 1-min interval at a flow rate of 2.83 L/min. Meanwhile, the Gasman Portable Gas Detector was used to obtain O3 measurements of indoor air. Other than that, temperature and relative humidity (RH) were also measured to determine the thermal comfort, by using the Vaisala HUMICAP Hand-Held Humidity and Temperature Meter (model HM70).

The IAQ survey at the shopping malls was conducted on from March to April 2015. Each shopping mall was visited four times, which is on two weekdays and two weekends, with a sampling duration of 8 h (11 am–7 pm).[6] Indoor and outdoor air samples were taken within a half an hour range. Each range was conducted every 10 min to obtain representative data. The ground floor of each shopping mall with a relatively high flow of shoppers was selected for this study. Indoor samples were collected at discrete but representative sampling locations, as close as possible to the central positions of selected floors. On the other hand, outdoor samples were taken at street levels in close proximity to the fresh air intake, which was the front entrance at the ground level for both shopping malls. The sampling probes of air monitoring equipment were placed at a height of approximately 1.5 m above the ground and also kept away from any source of targeted air pollutant. During sampling, various indoor parameters including the numbers of floors, numbers of shops, floor area, and ventilation type were recorded.


[Figure 1], [Figure 2], [Figure 3], [Figure 4] show the average indoor and outdoor PM concentrations of different sizes (PM0.3-∞, PM0.5-∞, PM2-∞, and PM5-∞) at the shopping malls, measured on weekends and weekdays. As a whole, the overall average of indoor PM0.3-∞concentrations for all shopping malls on weekdays and weekends was 386.39 ± 155.24 µg/m3 and 421.44 ± 102.96 µg/m3; PM0.5-∞ was 31.67 ± 27.13 µg/m3 during weekdays and 41.75 ± 15.54 µg/m3 during weekends; PM2-∞ was 1.06 ± 0.54 µg/m3 and 1.30 ± 0.41 µg/m3 on weekdays and weekends; and PM5-∞ concentrations for all shopping malls were 0.14 ± 0.07 µg/m3 during weekdays and 0.21 ± 0.09 µg/m3 during weekends, respectively.

Figure 1: Comparison of average PM0.3-∞ concentrations between indoor and outdoor on weekdays and weekends

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Figure 2: Comparison of average PM0.5-∞ concentrations between indoor and outdoor on weekdays and weekends

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Figure 3: Comparison of average PM2-∞ concentrations between indoor and outdoor on weekdays and weekends

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Figure 4: Comparison of average PM5-∞ concentrations between indoor and outdoor on weekdays and weekends

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On weekdays, the average indoor concentrations of PM0.3-∞ at the three sites ranged from 218.51 ± 27.06 µg/m3 to 563.94 ± 61.98 µg/m3, which were slightly lower than outdoor concentrations which ranged from 253.42 ± 66.29 µg/m3 to 461.94 ± 95.23 µg/m3. The indoor concentrations on weekends ranged from 321.14 ± 100.52 µg/m3 to 495.68 ± 40.67 µg/m3, while the outdoor concentrations had lowest value of 216.54 ± 53.74 µg/m3 and the highest value of 437.45 ± 94.76 µg/m3. The lowest value was recorded in SM3 on weekdays and in SM2 on weekends. The indoor concentrations of PM0.5-∞ on weekdays ranged from 10.87 ± 3.15 µg/m3 to 65.80 ± 19.22 µg/m3 and on weekends 24.72 ± 8.07 µg/m3 to 51.18 ± 9.27 µg/m3, which were slightly higher than the outdoor concentration which ranged from 15.31 ± 2.75 µg/m3 to 52.70 ± 48.34 µg/m3 on weekdays and 25.36 ± 6.12 µg/m3 to 40.01 ± 11.08 µg/m3 on weekends.

The concentrations of PM with bigger aero-diameters (PM2-∞ and PM5-∞), the average indoor PM2-∞ concentrations, recorded at the three sites on weekdays ranged from 0.54 ± 0.14 µg/m3 to 1.65 ± 0.41 µg/m3. Average outdoor concentrations obtained were higher than indoor, ranging from 1.52 ± 0.35 µg/m3 to 1.99 ± 0.44 µg/m3. On weekends, the highest and lowest average indoor PM2-∞ concentrations were recorded at 1.59 ± 0.50 µg/m3 and 0.97 ± 0.17 µg/m3, respectively, which were slightly lower than the outdoor concentrations ranging from 1.34 ± 0.30 µg/m3 to 5.64 ± 0.43 µg/m3. Indoor PM5-∞ concentrations recorded ranged from 0.07 ± 0.02 µg/m3 to 0.21 ± 0.05 µg/m3 on weekdays and 0.13 ± 0.02 µg/m3 to 0.28 ± 0.08 µg/m3 on weekends, which were slightly lower than outdoor ranging from 0.10 ± 0.03 µg/m3 to 0.25 ± 0.05 µg/m3 on weekdays and 0.14 ± 0.05 µg/m3 to 0.24 ± 0.05 µg/m3 on weekends. For all the observed sites, SM1 had the highest average indoor concentrations of PM sizes on both weekdays and weekends.

Ozone concentration measurement was carried out indoor and outdoor of shopping malls. No ozone was detected in all the indoor environments of the three sampling sites. The range of average outdoor ozone concentration detected was 0.009 ± 0.003 ppm to 0.019 ± 0.008 ppm on weekdays and 0.007 ± 0.005 ppm to 0.012 ± 0.004 ppm on weekends as shown in [Figure 5]. Both weekdays and weekends recorded a quite constant outdoor ozone concentration throughout the 8-h sampling duration, with lowest being 0.00 ppm and highest 0.04 ppm. None of the shopping malls exceeded the standard ICOP-IAQ 2010 of indoor ozone level of 0.05 ppm. Meanwhile, the outdoor ozone concentrations recorded were also below the ambient ozone standard recommended by the Malaysian Ambient Air Quality Guidelines of 0.06 ppm (8-h average).

Figure 5: Comparison of ozone concentrations between indoor and outdoor on weekdays and weekends

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Construction activities were conducted nearby SM1 during sampling, which contributed to fugitive PM emissions and hence, significantly increased the ambient suspended PM.[10] The presence of wind blew these emissions to adjacent premises, which caused the elevated outdoor concentration of PM at the shopping mall.[11] In a study carried out in China, the possibility of infiltration of ambient air into shopping mall is shown, causing the rise of indoor pollutants level.[1] Infiltration of outdoor air via building leakage, air exchange rate (ventilation) in the building from re-suspension of road as well as soil dust from outdoor are responsible factors for higher PM concentrations in indoor environment.[4]It is also reported that PM concentrations were highest in those retail environments that were in the closest vicinity to smokers and gas stoves, especially malls with the restaurants therein.[9] The presence of indoor sources for fine fraction PM is mostly due to combustion sources (cooking) and generates from some semi-volatile organic compounds originating from restaurant shops inside shopping malls.[7]

It also strongly suggested that indoor sources are the main contributor to indoor PM especially resulting from combustion sources[12] and higher physical activities in the shopping mall especially due to a higher number of occupants on weekends.[13] It was anticipated that human presence and related activities would represent a significant source of ultrafine particles indoors.[14] The study conducted in Thailand at shopping malls also reported the higher indoor PM level during the weekends due to more crowded conditions; human bioeffluents from the crowd may contribute substantially to the high levels of PM.[15] On both weekdays and weekends, the poor correlation between indoor and outdoor air in the shopping malls, especially in SM1, is linked with the presence of high indoor PM levels and poor direct access to outdoors, which indicate the need for a better ventilation system in the shopping mall.[15],[5]

No ozone was detected in the indoor environment, which indicated that there were very low levels of indoor ozone in all the three sites. The absence of major sources such as ozone generators or very few photocopy machines present in the shopping malls may result in lower indoor ozone concentrations.[16] Furthermore, indoor ozone concentrations could also be reduced due to the deposition of ozone on various surface materials and chemical reactions.[17],[18] Meanwhile, the average outdoor ozone concentration was higher than indoor in all the three shopping malls on both weekdays and weekends, since a large fraction of outdoor ozone is derived from photochemical processes in the atmosphere.[19]


IAQ of shopping malls has been characterized in terms of the mass concentration level of different sizes of particulate matter (PM0.3-∞, PM0.5-∞, PM2-∞, and PM5-∞). PM concentrations were found to be highest in SM1 on both weekdays and weekends, compared to SM2 and SM3. A poor ventilation system in SM1 affected the IAQ by increasing the PM accumulation, besides indoor sources such as cooking activities and higher human activities on weekends. In addition, the ozone level was also determined in the three shopping malls for the characterization of IAQ. No indoor ozone was detected in all sites, suggesting very low indoor ozone levels, probably due to the absence of major sources such as ozone generators and the deposition of ozone on various surface materials and chemical reactions. The average outdoor ozone levels at all shopping malls were also below the recommended acceptable concentration of 0.06 ppm in Malaysian Ambient Air Quality Guidelines.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ATMPH.ATMPH_72_17


[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

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