In this article, the principles or airflow control (PID) are researched as a function of altering room temperature. The research provides a method for room temperature estimation. The article explains a calculation of supply air temperature, required to produce the requested temperature in a hospital operation rooms after being mixed with room air. Researches will be made and results obtained, showing that at a smaller supply air volume a wider difference between supply and set point temperatures is needed and vice versa – at sufficient volume, the temperature may differ just slightly, the ideal solution being when the air with the requested temperature fully replaces the air with unacceptable temperature.