Introduction. Biological personal protective equipment (PPE) is currently in particular demand, primarily when working with patients with a new coronavirus infection (COVID-19). Many materials used in the manufacture of such PPE have low air and vapor permeability, which ultimately can contribute to overheating of the body even in a comfortable temperature environment. The aim of study — physiological and hygienic assessment of the thermal state of the body of medical workers dressed in PPE from biological factors during the working day. Materials and methods. The study was conducted on the basis of an infectious hospital clinic of the FSBSI "Izmerov Research Institute of Occupational Health" during the COVID-19 epidemic on practically healthy volunteers: orderlies, nurses and doctors, who during the study performed their duties in the "infectious" zone. Results. The volunteers were equipped with sensors that measure the temperature of the skin and body, heart rate and humidity of the underwear. The indicators obtained during the experiment were evaluated in accordance with the current regulatory documentation. Conclusion. The data obtained as a result of the study showed an increase in most of the criteria indicators of the thermal state of the body of medical workers, which made it possible to assess the intensity of the thermal state of medical personnel.