Device for testing the sealing of at least one system for insulating two mediums in a sealed manner, the system including a flange and a sealed door mounted in the flange, the test device including a casing including an inflatable seal intended to contact, in the inflated state, with the system and to ensure a sealing enabling the definition of a test volume between the system and the casing, a pneumatic pump and a pneumatic circuit configured to connect, in a first step, the pump to the inflatable seal such that the pump inflates the inflatable seal, and in a second step the pump to the test volume such that the pump generates in the test volume a pressure at a given value, and sensor for measuring the pressure in the test volume.