An adsorbent system including an enclosure having a cavity defining a humidity-controlled environment and a body having or defining a channel therein. The body is coupled to the enclosure such that a first end of the channel is in selective fluid communication with an ambient environment and a second end of the channel is in fluid communication with the humidity-controlled environment. The system further includes an adsorbent material in the channel, wherein the channel and adsorbent material are configured such that inlet fluid flowing from the first end to the second end through the channel is flowable over at least a portion of the adsorbent material, and such that outlet fluid flowing from the second end to the first end is directly flowable over a majority of the portion of the adsorbent material that is flowable over by the inlet fluid, The system further includes a valve system positioned at or adjacent to or in fluid communication with the first end of the channel. The valve system includes an inlet valve portion that is biased to a closed position to generally block a flow of inlet fluid therethrough and that is movable to an open position when a pressure in the channel is sufficiently low relative to a pressure in the ambient environment. The valve system further includes an outlet valve portion that is biased to a closed position to generally block a flow of outlet fluid therethrough and that is movable to an open position when the pressure in the channel is sufficiently high relative to the pressure in the ambient environment.