Reverse circulation drilling is similar to air core drilling. The cuttings are returned to the surface through an inner tube and collected for later use. This type of drilling is done by either rotary drilling or percussion drilling with the aid of a down hole hammer. Reverse circulation drilling is a highly utilized drilling method for mineral exploration. RC is used to retrieve continuous samples from the ground where a solid core is not needed. In RC drilling, air, or sometimes water, is pumped into a side inlet air swivel. The air is then blown down the outside of the pipe. Once the air hits the drill bit, it flushes and cools the air but also creates a vacuum that forces the air and cuttings up the center of the drill string and into the inner tube sampler
