Investigation Of Indoor Air Quality And Thermal Comfort In Mosque Buildings
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Date
2019-08-01
Authors
Rasli, Nur Baitul Izati
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The mosque is a symbolic landmark where the Muslim community mainly
prays five times a day and performs other social and cultural activities. However, the
widespread use of Air Conditioning Split Units (ACSUs) to cool the indoor air in
mosques may pose potential adverse health effects for users. Therefore, a
comprehensive investigation was conducted to identify the indoor air quality (IAQ),
thermal comfort (TC), and biological contaminants (bacteria and fungi) in the typical
mosque buildings in Malaysia, within different ventilation conditions (ACSUs and
non-ACSUs) at lowland and highland areas. The study was conducted from 1200 h
to 1700/1730 h to assess 35 mosques during Zohor-Asar and Friday-Asar prayers
times. The recorded IAQ parameters were evaluated for their compliance with
Malaysia’s Industrial Code of Practise (ICOP) 2010, whereas the predicted mean
vote (PMV) and percentage of people dissatisfied (PPD) were used to assess thermal
comfort by using the ASHRAE’s CBE thermal comfort tool. The effectiveness of
ventilation strategies in reducing temperature in the main prayer halls were evaluated
based on four categories: 1) roof design (Ottoman, Pyramidal, and Iran and Middle
East styles), 2) ventilation conditions (ACSUs and fans), 3) window-to-wall ratio
(WWR) and 4) percentage of dead walls. Next, the biological contaminant levels
were also compared with ICOP’s acceptable limits and their types were identified
using the ID Microgen software. Lastly, to improve IAQ and thermal comfort, the
movement of outdoor air toward indoor were visualized by using the smoke flow
visualization technique. The results showed that mean concentrations of indoor air
contaminants (TVOC, CH2O, CO, PM10, and CO2) were still within the acceptable
limits recommended by ICOP, except for the mean of O3 concentrations. The mean
of O3 concentrations exceeded the acceptable limit by ICOP at 0.13±0.02 ppm
(lowland ACSUs mosques) and 0.09±0.01 ppm (lowland non-ACSUs mosques)
during Friday-Asar prayers. The mean indoor air contaminants of four out of six
(TVOC, O3, CO, and PM10) at ACSUs mosques during Friday-Asar prayers were
higher compared to non-ACSUs mosques. Moreover, based on the obtained results,
the mosques at lowland (ACSUs and non-ACSUs) did not provide good thermal
comfort with the highest PMV and PPD values were 1.64-2.94 and 55-99%,
respectively at lowland ACSUs Pyramidal roof style mosques. Results obtained
from the lowland mosques showed that the percentage of dead walls (R2=0.99) had
the most effect that contributed to the high indoor air temperatures within the main
prayer halls. The next factor was WWR (R2=0.72). Meanwhile, the type of roof
design or ventilation condition had no significant influence on the reduction of high
indoor air temperature. Furthermore, the bacteria concentrations at lowland exceeded
the guideline set by the ICOP (500 cfu/m3) in ACSUs mosques (58.8%) were higher
than the non-ACSUs mosques (12.5%), whereas, at highland did not. The dominant
types of bacteria found in the lowland mosque were Staphylococcus spp. and Bacillus
spp. whereas for fungi was Aspergillus spp. and Aspergillus niger. Meanwhile, the
dominant types of bacteria found in the highland mosque were Staphylococcus spp.,
Bacillus spp., and Micrococci spp. whereas for fungi was Aspergillus niger and
Trichoderma spp. Therefore, window panel with double pores can be implemented
to allow outdoor air passing through indoor to improve better IAQ and TC in the
mosques buildings.