Abstract: A retaining device for improving the functionality of placard holders when the placard holder is subject to transient atmospheric conditions. The retaining device includes a member used in conjunction with a placard holder to more fully secure a placard with the placard holder when transient atmospheric conditions are encountered. The retaining device may be adapted to use with many designs of placard holders, including, but not limited to, U.S. Department of Transportation approved hazardous material information placard holders.