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[Display omitted] • This review compiled indoor PM concentration worldwide that mostly exceeded WHO guidelines. • Indoor PM derived mainly from combustion activities, human movement and outdoor sources. • More attention should be paid to the accumulation mode PM due to highly-penetrating and lowly-depositing. • The indoor/outdoor ratio of PM concentration was primarily affected by human activity and ventilation. • Reasonable ventilation, indoor sources control or using filtration-based air cleaners could reduce indoor PM concentration. Particulate matter (PM) refers to the sum of all solid and liquid particles suspended in the air, many of which are harmful. Exposure to indoor PM with high concentration may cause a series of adverse health effects. This review provides a comprehensive summary of characteristics and influencing factors of indoor PM, including concentration, indoor sources, penetration of outdoor PM, deposition onto indoor surfaces and air exchange rate. Indoor PM pollution is rather serious, and even the indoor concentration in some cities exceeds air quality standards recommended by the World Health Organization. Indoor sources can give rise to a sharp increase in indoor PM concentration, which greatly affects individual exposure and cannot be ignored. Accumulation mode particle is characterized by high penetration and low deposition, which pose a challenge to its control. Ventilation can migrate outdoor PM into indoor environment, especially when ambient PM concentration is high. In order to ensure the health and comfort of indoor built environment, measures should be taken to reduce indoor PM concentrations. Source control is the typical and effective way to control indoor PM. Natural ventilation is the most economically technical means of reducing indoor PM, although uncertainties remain as to its effectiveness for PM control. Filtration is the most well established and widely used technology for internal air cleaning due to its low cost and high efficiency. With the increasing health awareness of people, it is also recommended to clarify the impact of exposure to indoor PM on human health. [ABSTRACT FROM AUTHOR]