One-way pressure relief valves with wetting fluid reservoirs are disclosed. Valves of the types described herein may be applied to a product package, for example a package containing dry roasted coffee, to allow gas to escape from the package while preventing entry of ambient air into the package. A wetting fluid is provided within the valve to facilitate formation of the seal blocking entry of ambient air through the valve and into the product package. The wetting fluid reservoirs hold wetting fluid to limit or prevent leakage of the wetting fluid from the valve providing benefits such as improved application of the valves to the packages, improved retention of the valves to the packages, and appearance improvements resulting from avoidance of leakage of wetting fluid onto the valve and the package to which the valve is attached.