Calculation method of minimum outdoor air rate of mechanical ventilation for maintaining positive room pressure

 Establishes a stack pressure-driven single-sided ventilation model and a wind pressure-driven cross ventilation model. Investigates the relationship between the natural air infiltration rate and the outdoor air rate of mechanical ventilation under the two ventilation models through theoretical derivation. Concludes the calculation formula of the minimum outdoor air rate of mechanical ventilation required to maintain positive room pressure, and validates it by an experiment. The results show that the minimum outdoor air rate of mechanical ventilation required to maintain positive room pressure is 2.0 to 3.2 times of the natural air infiltration rate of a room without outdoor air supply for the stack pressure-driven single-sided ventilation, whereas the ratios are 1.2 to 2.5 times for wind pressure-driven cross ventilation.