Compliance of indoor air contaminants within the main prayer halls of mosques in Malacca with Malaysia's indoor air quality standard

This study examined the compliance of indoor air contaminants (total volatile organic compound [TVOC], ozone [O3], carbon monoxide [CO], formaldehyde [CH2O], particulate matter [PM1, PM2.5, PM5 and PM10] and carbon dioxide [CO2]) during Dhuhr/Friday and Asr prayers with the guideline limits in Malaysia's Industrial Code of Practice (ICOP). Monitoring was conducted from 12:00-5:00 p.m. in three prominent mosques in Malacca City, namely, M1 (a historic mosque; during Dhuhr at 1:07-1:18 p.m. to Asr at 4:31-4:42 p.m.), M2 (a historic mosque; during Friday at 1:38-1:48 p.m. to Asr at 4:33-4:50 p.m.) and M3 (a floating mosque on the Straits of Malacca; during Dhuhr at 1:12-1:27 p.m. to Asr at 4:33-4:50 p.m.). Results show that the mean concentrations of the nine indoor air contaminants in M1, M2 and M3 did not exceed ICOP's limits, except for the ozone concentration in M3 that exceeded the limit at 0.150 ppm. We conclude that the concentration levels of indoor air contaminants in the studied mosques are in compliance with Malaysia's ICOP and the non-compliance issue with regard to the ozone concentration in one of the mosques is due to the mosque's location in a busy coastal and marine area.