The technology disclosed herein relates to filter assemblies and methods of making filter assemblies. One filter assembly has a first sheet of filter media having a first perimeter region and a second sheet of filter media having a second perimeter region. The first perimeter region and the second perimeter region are bonded in a rim region. A plurality of adsorbent beads are disposed between the first sheet of filter media and the second sheet of filter media, and a substantial portion of the plurality of adsorbent beads are unbonded. Other embodiments are also described.