Introduction: The professional use of personal protective equipment (PPE) eliminates occupational exposure of personnel to pathogens that cause infectious diseases, including COVID-19. Apart from the risk of exposure to biological hazards, healthcare workers are at risk of impaired work performance and work-related diseases posed by adverse health effects of PPE itself. Objective: To make a physiological and hygienic assessment of personal protective equipment against biological hazards used by healthcare professionals. Materials and methods: We evaluated the thermal state of the body in 13 volunteers under simulated conditions of the Tabai temperature and humidity chamber (Japan). The study design included a physiological and hygienic assessment of four variants of protective suits, all compliant with recommendations of the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing (Rospotrebnadzor) for use when working with microorganisms of risk groups I and II. We studied the physiological response of the thermoregulatory system to heat exposures in terms of indicators characterizing the temperature of the “core”, the temperature of the “shell”, and their integral indicators (weighted mean skin and body temperatures). Changes in the fluid and electrolyte metabolism and the functional state of the cardiorespiratory system were assessed based on objective (sweat and heart rates) and subjective (heat sensation) indicators. Results: At the air temperatures of 25 and 30 °C, the maximum thermal exposure was registered in the volunteers wearing coveralls made of nonwoven material of the Tyvek type (China). A suit made of polyester fabric with a polyurethane membrane coating (Russia) had a less pronounced effect on the thermal state of the body. The minimum core and shell temperatures were noted for the suits made of polymer-viscose dustproof, water-repellent twill weave fabric (Russia) and Barrier 2X fabric (Russia). Conclusion: The excess of established values of the thermal state of the body during medium work was observed for all types of the studied suits both in permissible (25 °C) and harmful (30 °C) microclimate conditions. To prevent ill-being of medical personnel, it is necessary to schedule work taking into account the type of PPE used, the intensity of physical activity, and indoor microclimate parameters.