A valve assembly for use in a pneumatic network, includes a body having a first inlet port and a first air discharge port. A main duct includes a convergent portion, a restricted-section portion having a variable area of passage, and a divergent portion. An actuator assembly includes an intake volume and a second inlet port in fluid communication with the intake volume by valve means provided for enabling intake of a second fluid flow through the second inlet port and towards the intake volume, wherein the second fluid flow is drained off through the first discharge port together with the first fluid flow.