Objective To investigate the monitoring concentrations of indoor particulate matter in eight types of public places in Dongcheng district, Beijing, over the past six years, and to analyze the distribution characteristics of indoor particulate matter concentrations and their relationship with outdoor particulate matter.

Methods From 2019 to 2024, eight types of public places in Dongcheng district, Beijing, including hotels, beauty salons, hospitals, supermarkets, swimming pools, gyms, cinemas, and subway stations, were selected to detect indoor particulate matter concentrations according to the Examination Method for Public Places (GB/T 18204-2013). The Kruskal-Wallis H test was used to compare the differences in particulate matter concentrations across different years and places, and to analyze the influencing factors for particulate matter concentration.

Results The median concentrations of indoor inhalable particulate matter (PM₁₀) and fine particulate matter (PM_2.5) in major public places in Dongcheng district were 0.037mg/m³ and 0.026mg/m³, respectively. There were differences in the concentrations of indoor PM₁₀ and PM_2.5 between years and types of public places, with relatively high concentrations and relatively low qualified rates in subway stations and hospitals in 2019. There was a significant positive correlation between indoor and outdoor particulate matter concentrations (P < 0.05). The indoor-to-outdoor particulate concentration ratio (I/O value) was highest in subway stations, with a median of 1.19 and 1.12, respectively.

Conclusion The indoor PM₁₀ and PM_2.5 matter pollution in major public places in Dongcheng district is primarily composed of PM_2.5. Subway stations and hospitals, as special public places, should be taken seriously regarding their air quality.