In this thesis, the examination focused on the structural tightness of the hospital's operating room and the air leakage caused by its overpressurization through the structure. Additionally, the thesis reflected on the problems caused by uncontrolled air leakage and its effects on the entire building mass. The thesis also provided suggestions for the systematic management of this uncontrolled air leakage. In this thesis, there was also a review of existing current regulations and guidelines for the design and sizing of ventilation in operating rooms in hospitals.

Only a limited number of instructions are available for the design of ventilation in operating rooms. The current legislation on the ventilation of buildings applies to the ventilation of operating rooms only on a general level, and the ventilation of these special areas is currently designed based mainly to experience of the HVAC designer.

The airtightness of structures is significant not only for the outer envelope of the building, but also for specialized areas where maintaining different pressure levels is required. The amount of air leakage and controlling it become more crucial in these spaces, depending on the surface area of the room envelope, the air leakage rate of the room and the desired pressure difference across the structure.

As a result, a new system-level modification was developed for the ventilation of operating rooms, allowing the measurement and controlled elimination of the air leakage volume in the operating rooms. Uncontrolled leakage air from the operating room can only be controlled up to a certain point with various ventilation technical solutions. The primary means of controlling this air leakage should be the structural airtightness of operating rooms and it´s verification.

To control and eliminate air leakage in the operating rooms, the air leakage rate must be verified and measurable. A clear target value for the airtightness of the operating room should be set during the design phase. The final airtightness of the operating room should be measured as early as possible during the construction phase so that any necessary additional sealing can be applied to achieve the target values of structural air leakage rate.