Leak detection device having a dome with a main body and a seal configured to define a detection chamber between the main body and the test zone, the seal including a peripheral sealing lip configured to come into contact with the sealing membrane and having a closed contour encircling the detection chamber, an analysis tool connected to the detection chamber to analyze a gas present in the detection chamber in which the sealing lip is configured to have at least in a service state in which a reduced pressure is applied in the detection chamber, a pinch portion that is pinched between the main body and the sealing membrane.