A device for testing the sealing of an installation (70, 80): - of the type comprising a tank intended to store a first fluid in an interior space of this tank, or - of the type comprising two pipes (81, 82) and a junction between these two pipes, these pipes being intended to transport a first fluid in an interior space of these pipes, this device comprising: - a pressurisation system arranged to pressurise a test fluid in the device, and - a pressure measuring system arranged to measure the pressure of the test fluid in the device, this device further comprising: - a pressurisation chamber, and - a first sealing element arranged to isolate the pressurisation chamber from said interior space (711, 811), the pressurisation system being arranged to pressurise the test fluid in the pressurisation chamber, and the pressure measuring system being arranged to measure the pressure of the test fluid in the pressurisation chamber, being characterised in that the pressurisation chamber is annular and delimited by a fixing flange, and in that the device further comprises a cover (3, 73) and the fixing flange (4, 74), the fixing flange being arranged on the tank to fix a cover (3, 73) to the tank, the fixing flange (4, 74) being arranged to fix the cover (3, 73) to the tank, the cover (3, 73) and the fixing flange (4, 74) being arranged to delimit the pressurisation chamber, or in that the fixing flange is arranged on a pipe to form a junction with the fixing flange of a pipe, these fixing flanges (831, 832) being arranged to fix the two pipes (81, 82) together, and to delimit the pressurisation chamber. - of the type comprising a tank intended to store a first fluid in an interior space of this tank, or - of the type comprising two pipes (81, 82) and a junction between these two pipes, these pipes being intended to transport a first fluid in an interior space of these pipes, this device comprising: - a pressurisation system arranged to pressurise a test fluid in the device, and - a pressure measuring system arranged to measure the pressure of the test fluid in the device, - a pressurisation system arranged to pressurise a test fluid in the device, and - a pressure measuring system arranged to measure the pressure of the test fluid in the device, this device further comprising: - a pressurisation chamber, and - a first sealing element arranged to isolate the pressurisation chamber from said interior space (711, 811), - a pressurisation chamber, and - a first sealing element arranged to isolate the pressurisation chamber from said interior space (711, 811), the pressurisation system being arranged to pressurise the test fluid in the pressurisation chamber, and the pressure measuring system being arranged to measure the pressure of the test fluid in the pressurisation chamber, being characterised in that the pressurisation chamber is annular and delimited by a fixing flange, and in that the device further comprises a cover (3, 73) and the fixing flange (4, 74), the fixing flange being arranged on the tank to fix a cover (3, 73) to the tank, the fixing flange (4, 74) being arranged to fix the cover (3, 73) to the tank, the cover (3, 73) and the fixing flange (4, 74) being arranged to delimit the pressurisation chamber, or in that the fixing flange is arranged on a pipe to form a junction with the fixing flange of a pipe, these fixing flanges (831, 832) being arranged to fix the two pipes (81, 82) together, and to delimit the pressurisation chamber.