Ethylene is produced by fruits and vegetables as a signaling mechanism to coordinate uniform ripening. When it accumulates in the refrigerator or other storage areas, it accelerates ripening and, consequently, the spoilage of vegetables and fruits. Read more about ethylene here.
The refrigerator deodorizer with zeolite is designed to provide effective absorption of this gas in a typical household refrigerator for about three months. The active ingredient of the zeolite it contains does not "decompose" and continues to absorb ethylene until it reaches its saturation point.