markets were selected for this study. The indoor air pollutants measured included PM (particulate matters with 10
aerodynamic diameter less than 10 mm), total bacteria count (TBC), carbon monoxide (CO), nitric oxide (NO),
nitrogen dioxide (NO ) and sulfur dioxide (SO ). The indoor and outdoor concentrations of these target air pollutants 2 2
at these markets were measured and compared. The effects of air conditioning, temperatureyrelative humidity variation
and different stalls on the indoor air quality were also investigated. The results indicated that all of the average
indoor concentrations of PM , TBC, CO and NO at the markets were below the Hong Kong Indoor Air Quality 10 2
Objectives (HKIAQO) standards with a few exceptions for PM and TBC. The elevated PM concentrations at 10 10
Hung Hom, Ngau Tau Kok and Wan Chai markets were probably due to the air filtration of outdoor airborne
particulates emitted from vehicular exhaust, whereas high concentrations of airborne bacteria at Sai Ying Pun and
Tin Shing markets were linked to the use of air conditioning. Correlation analysis demonstrated that indoor bacteria
concentrations were correlated with temperature and relative humidity. The operation of air conditioning did not
significantly reduce the levels of air pollutants at the markets. However, the higher indooryoutdoor ratio
