In terms of very fine particle filters (pore sizes at about 0.2 micron), there seem to be some filters marketed/labeled to be for "air" (hence gases) and others for syringes (hence liquids)
- example for gas filter Omicron 200050R PTFE Venting
- example for liquid filter Whatman 6900-2502 GD/X 25 Sterile Syringe Filter
To a layman as myself it is hard to see at a glance the necessary difference. What are those differencs?
One potential difference I have spoted so far is that as it was stated on http://omicronscientific.com/ the "air vent filter" is hydrophob, which I guess would make it impracticle for being used as liquid filter, when used with certain liquids.
There are filters used for gases