A vented vial adapter for retaining aerosols when accessing a vial having a pierceable seal located over an opening of the vial, the adapter comprising: a flexible attachment device configured to engage the vial for secure mounting of the vial adapter to the vial； a cannula on the attachment device, the cannula having a sharpened tip configured to pierce the seal of the vial, a vent opening adjacent the sharpened tip, a slot, and a medicament opening on the slot, the vent opening leading to a vent lumen extending through the cannula, the medicament opening leading to a medicament lumen extending through the cannula； a body portion having a valve in fluid communication with the medicament lumen of the cannula, the valve biased to a closed orientation and configured to allow liquid to be introduced into and removed from the vial when the valve is actuated to an open orientation； and an elongate filter chamber having a first opening and a second opening, the first opening in fluid communication with the vent lumen of the cannula, the filter chamber containing a first filter device and a second filter device, the first filter device disposed between the first opening and the second filter device and configured to allow passage of liquid dispersed in gas to the second filter device while blocking non-dispersed liquid, the second filter device disposed between the first filter device and the second opening and configured to absorb liquid dispersed in gas.
