A multistage proportional valve (10) for controlling the pressure of a fluid inside a container (12) includes a fluid outflow passageway (22) having an exhaust opening (24), an actuatable fluid inflow passageway (38) having an intake opening (46) and an actuatable exhaust cover (30) for selectively closing said exhaust opening (24). The fluid outflow passageway (22), actuatable fluid inflow passageway (38) and actuatable exhaust cover (30) are interconnected and configured such that in response to an actuating force reaching a first pre-determined threshold the valve (10) displaces the exhaust cover (30) to allow the fluid inside the container (12) to exhaust there from through the fluid outflow passageway (22). In response to the actuating force reaching a second pre-determined threshold the valve (10) displaces the fluid inflow passageway (38) to allow pressurized fluid to flow there through inside the container (12).