Abstract:Abstract: OBJECTIVE To systematically learn about indoor air quality in public places in Qingdao, and to grasp the daily variation of the main hazard factors in different public places. METHODS Online continuous monitoring equipment was used to monitor PM 2.5 , PM 10 , NO 2 , O 3 , NO, CO, noise, temperature and relative humidity in 6 key public places in Qingdao for 24 hours. RESULTS The concentrations of particulate matter in hotel rooms fluctuated between low in the day and high in the night, while that in hotel lobbies was high in the day and low in the night. PM 2.5 exceeded the standard in the rooms at night and in the lobby during the day, accounting for 8.3% ~12.5% of the whole day. The O 3 concentrations at the monitoring points of hotel lobbies,gyms and transportation hubs were high and the daily variation were large,NO 2 as a whole presents a higher daytime than night feature,with distinct double peaks observed in the hotel lobby and transportation hub waiting room. The noise in each public place was higher in the day than at night, the qualified rate of hotel rooms was less than 25.0% , and 100.0% of supermarkets exceed the standard. CONCLUSION The online continuous monitoring shows that the indoor health hazard factors in public places have obvious daily changes,among which the problem of excessive noise is the most prominent,Indoor activities or movement of people and outdoor environment are the possible factors causing diurnal variation.