Food grade and sanitary air blow check valves meet 3-A or NSF (National Sanitation Foundation) 51 standards for use with dairy or food and beverage products. They evacuate residual media from system lines in Clean-In-Place (CIP) applications to maintain sanitary standards and prevent line corrosion. Air pressure pushes on the rubber plug attached to a spring-loaded stem away from the seat. When there's no air pressure present in the valve, the spring-loaded stem pushes the plug back into the seat, preventing media from entering the line.