Nowadays, indoor air quality is no longer considered as providing thermal comfort. The pollutant concentration in the ambient air (CO2, O3, particulate matter, etc.) is an essential factor affecting both indoor air quality and human health negatively. Particle motion in a room is affected by air movements caused by heating systems and infiltration and needs to be examined. Therefore, this study aims to explain how infiltration rates in a room with floor heating affect both thermal conditions and particularly the particle concentration and distribution. In this study, the discrete phase model (DPM) was used for particle tracking using commercial software ANSYS FLUENT. It was assumed that drag, lift, thermophoretic and Brownian forces were affecting particle motions. It was seen that air change rates influence both thermal comfort and energy consumption as well as particle distribution significantly. It was found that increasing air change rates causes a rise in particle concentration in all sizes of particles, specifically for the lower parts of the room (below 0.75 m from the floor). It is recommended to place air purifying devices where the outdoor sourced air infiltrates the room. Additionally, an index that contains thermal comfort and particle concentration together was defined and its distribution in the room was examined. It is found that the air change rate is a critical factor in obtaining desired indoor air quality, but outdoor air conditions may worsen the indoor quality due to air pollution. As the air change rate significantly alters the airflow in the room, both thermal comfort perception and particle concentrations vary considerably.