A pressure relief valve for pressure equalization between a closed space and the surrounding atmosphere comprises a valve housing (1) with an upwardly facing blow-off opening (11) in which a conical valve seat (13) is formed. A drop-shaped body (14) arranged in the blow-off opening (11) is formed on its underside with a conical valve surface (15) co-operating with the valve seat (13). The drop-shaped body is connected with a lifting disc (21) which has a larger area than the valve seat (13) and is surrounded by a free passage slot (22). The valve housing (1) has an inner configuration (8, 9, 10) such that the free passage area around the lifting disc (21) is decreased when the drop-shaped body (14) and the lifting disc (21) are lifted from the fully closed to the fully open position.