Abstract: A vaccum-breaking valve comprising: a tubular body (10) mounted through one of the walls (P) of the cabinet (G) and having inner (11) and outer (12) ends, a valve seat (15) defining a fluid communication between the inside and the outside of cabinet (G); and a seal constantly biased towards a closed position, blocking said fluid communication and dispalceable towards an open valve position. The seal comprises a slide (20), which is axially and slidingly mounted through the valve seat (15) and has a surrounding sealing ring (25), which is seated against the valve seat (15) when the slide (20) is displaced to the closed seal position, the slide (20) being provided with at least one air passage (24) interconnecting the upstream and downstream sides of the valve seat (15) when the slide (20) is in the open seal position.