Abstract: An anti-pack out seal for use between fluid containing cylinders and pistons which are axially slideable therein and which extend through an opening in the end of such pistons. This seal has an annular channel adjacent to a resilient elastomeric seal ring, through which channel, an air stream containing an oil mist is circulated to remove solid particles of material which may separate or pack out from the fluid in the cylinder and in addition to prevent curing of the solid particles between the cylinder, the elastomeric seal and the bearing surrounding the cylinder.