To provide a gas treating device operated in treating cycle.

A part of cycle is especially a PSA, a TSA or a VSA device provided with one or plural gas treating vessels having an adsorbent, and treatment is attained at lower pressure than atmospheric pressure. Respective vessels are provided with at least one orifice, at least one gas pipe communicated to the orifice and at least one valve arranged at the gas pipe and controlling the gas flow of the gas flowing through the pipe. The valve is provided with a means for operating the valve and a sealing means. The means for maintaining a protective gas atmosphere is arranged around the sealing means and the means for operating the valve, the penetration of a soil harmful to the adsorbent into the treating vessel is prevented, and especially the penetration of the moisture liable to inactivate molecular sieves, that is the adsorbent, so that the protective gas atmosphere may be formed and maintained around these.