Inside a power plant, fire is the most frequent aggression that can occur. In confined buildings, a fire can cause the rise of the pressure that is able to damage the division between buildings by breaking fire doors. EDF wrote 3 reports dealing with the issue of pressure caused by a fire that present the creation of a screening method to discriminate the rooms without risk and the detailed analysis for the rooms that are not discriminated. After investigation from the IRSN and the ASN, EDF had to change some parameters of the study such as the leakage surface considered for fire doors that needed to be reduced.