It is made of polytetrafluoroethylene (PTFE),patented design utilizes moulding,self-sealing mechanism,no O-ring inside therefore cross-contamination is eliminated. The connector of PTFE straight-through valve is vertical to the bag film,external diameter is 6mm. When the handle is vertical position, the valve is open, when the handle is parallel position, the valve is closed. PTFE straight-through valve is easy and swift to handle, and sealing tightly,the connecter can instal sample cap,which with silicone septum used for syringe sampling and vacuumizing. It suitable for filling inorganic and organic gases which are not corrosive to PTFE. The sample cap has a silicone septum that can be used for syringe sampling,the gas in the bag can’t touch the silicone septum in sample cap,so the gas can’t be polluted,the PTFE valve can be used in analysis high accuracy low concentration gas samples collection and preservation.Gas sampling bag with PTFE straight-through valve has won the national patent.