Abstract: An air treatment filter element is produced by contacting an adsorbent material selected from zeolite, activated carbon or a combination thereof with a liquid for inhibiting the growth of microorganisms. Additionally, the adsorbent material may include silica gel. Preferably, the liquid includes a fungicide/bacteriocide preservative composition in an amount from about 0.5 to 2% by weight of the liquid, at least one polyhydric alcohol, the polyhydric alcohol being present in an amount from about 83 to 99.5% by weight of the liquid, and at least one additional compound for modifying the vapor pressure of the polyhydric alcohol, the additional compound being present in an amount from about 0 to 15% by weight of the liquid. The amount of liquid used is from about 5 to 50%, most preferably 20 to about 30%, by weight of the combined weight of the liquid and adsorbent material.