By letters dated May 16, 2014, Agility Fuel Systems, Inc. (Agility) has notified the agency that it is conducting two safety recalls (NHTSA Recall No. 14E-025 and 14E-026) to address safety defects in certain compressed natural gas (CNG) equipment sold for use in certain heavy-duty truck applications.Safety recall 14E-025 addresses potentially defective CNG fuel container manual shutoff/ isolation valves manufactured by Young Do Industrial Co., Ltd. (Young Do).Approximately 462 vehicles were equipped by Agility with 829 subject Young Do valves between September 2010 and January 2013.When the valve is closed it may remain stuck in the closed position due to the valve seat becoming detached from the valve stem, thus blocking the flow of fuel from the fuel container to the engine.Such a condition poses a safety risk primarily to service personnel as there is no safe way to depressurize the fuel system and service the subject valve when it is stuck in the closed position.There may also be a small fuel leak through the valve stem when the valve seat becomes detached. The affected fuel container may also become over-pressurized if the stuck valve goes undetected for a period of time, or is not repaired in a timely manner, and the ambient temperature increases significantly. To date, Agility has repaired 566 of 829 potentially defective Young Do valves on 216 vehicles.The remainder will be repaired by Agility free of charge by installing a new valve seat and stem assembly.Safety recall 14E-026 addresses potentially defective CNG frame rail side-mount fuel container mounting straps that may become loose.Approximately 566 vehicles were equipped by Agility with 1,036 subject fuel container mounting systems between September 2010 and January 2013. A loose fuel container may experience abrasion damage.High-pressure fuel and vent lines may also become compromised, increasing the risk of fuel container rupture, fuel leak, disruption of fuel flow to the engine (possibly resulting