YSDT - LP-Gas Shutoff Valves are UL listed and approved and as per UL 1769 Standard. The valves are available with OPD for 20 lbs, 30 lbs and 40 lbs cylinder. An Overfill Prevention Device (OPD) valve on propane cylinders offers several important advantages: The primary advantage of an OPD valve is enhanced safety. The valve prevents the overfilling of propane cylinders by shutting off the flow of gas once the cylinder reaches 80% capacity and the QCC outlet ensures secure connection between the Regulator and the valve to avoid leaks.