Abstract: A dual-action vent check valve is disclosed. The valve includes a first check valve which is responsive to elevated fluids inside the valve. A second check valve is responsive to elevated fluids external to the valve. The first check valve prevents overflow from a vented structure, such as a sewer out-fall line, from passing through and out of the valve, thereby preventing spills. The second check valve operates to prevent floodwater from passing into an underground structure, such as a sewer, through the vent. One embodiment of the invention includes a basket for enclosing a deodorizing material inside the valve for deodorizing gases which pass through the valve.