A vented vial adapter has a filter attached to a vent arm that includes at least two filter media for suppressing aerosolized medicaments from leaving the vial and suppressing bacteria and other contaminants from entering the vial during reconstitution activities of the medication in the vial. The filter media allows the passage of air to the atmosphere outside the vial for pressure equalization. In another aspect, a third filter medium is used in the vent of the adapter to allow gas to pass in either direction through it, but prevents bacteria and particulate matter in the atmosphere from reaching the second filter device. A first filter is hydrophobic and prevents non-dispersed liquid from reaching the second filter, while conducting liquid dispersed in gas. The second filter absorbs the liquid dispersed in gas.