Bellerophon,mounted on Pegasus(q.v.),kept up in the air out of the way of the Chimaera, but yet near enough to kill it with his spear, or, as he is at other times represented,with his sword or with a bow.
When the ground-water rises it forces air out of the soil; when it falls again it leaves the soil moist and full of air.
A blower then pushes the cold air out into the room.
It's like using your lungs to draw the air out of a plastic milk bottle.
The filtered oil can then be stored in smaller containers with sealable lids to keep air out.