A cooling system for electrical and electronic devices for hot swapping of a fan module without affecting cooling efficiency due to air backflow, preventing stalling of newly installed exhaust device due to reverse rotation. A check valve assembly having an inlet side frame member, an outlet side frame member, and one or more non-symmetrical valve flaps, each flap having a movable part and a fixed part. The outlet side frame allows the flaps to open under suction pressure on side of the outlet side frame, the inlet side frame disallows the flaps to open under suction pressure on side of the inlet side frame, allowing air to flow in one direction from inlet side frame side to outlet side frame side only. The check valve assembly can be independent of the exhaust device. The check valve assembly can prevent backflow of air during hot swapping of the exhaust device.