This work is focused on monitoring the perception of indoor environment quality in the classroom. The research was carried out within the framework of the authors' internship at the Lviv Polytechnic in Ukraine in March 2019. The experimental measurements were carried out in the selected teaching class. In this article, there are presented the results of measurements, that were carried over three teaching hours with varying numbers of students. The measurements recorded by the means of measurement devices were: the air temperature, the relative humidity and the concentration of carbon dioxide in the interior of the classroom. At the same time as the objective measurements, a subjective evaluation was conducted. At the beginning and at the end of the lesson, the students and teacher completed the questionnaires about their perception of the internal environment. The results of the subjective assessment were compared with the measured values of the objective evaluation. Completion of the research is oriented on the perception of temperature and smell in the classroom, as well as overall satisfaction with the internal environment of the selected room.