According to reports from the scientific, public health and medical communities around the world, the quality of ambient and indoor air has a significant impact on the health of the population. Maintaining adequate indoor air quality in accordance with the standards set by the European Union and the WHO guarantees a reduction in the risk of many diseases and improved work capacity. It is extremely important to assess the air quality in schools. This is because during adolescence, the body undergoes significant development, making it particularly susceptible to harmful factors. The purpose of this study was to assess the indoor air quality based on physical, chemical and particulate pollutants present in the air in classrooms at an elementary school. The measurement was carried out using an IAQmeter, designed and manufactured by employees of the Faculty of Environmental Engineering at Lublin University of Technology, which allows continuous measurement and recording of temperature, humidity,CO2, SO2, NO2, VOCs (volatile organic compounds), formaldehyde, PM 2.5, and PM 1. The study was conducted for grades I-III, where students go out only at break and continue in the same room throughout the day. In addition, the factors that can affect the concentration of pollutants, such as ventilation or prolonged opening of doors, were monitored. Sensors were placed in the room, in the corridor and outside the room. The study showed that while spending time at school, students are exposed to a number of factors that can affect their well-being and health, which is best illustrated by the CO2 concentrations. The results of the study show that for more than 90% of the time spent at school, children are in indoor environments where the carbon dioxide concentrations exceed 1,000 ppm. It was also shown that the indoor environment in corridors is of lower quality than the environment in classrooms. The designed device enabled rapid measurement, recording a wide range of pollutants.