The sinuses are air-filled cavities. 1  They are located: 2  Within the bony structure of the cheeks. 3  Behind the forehead and eyebrows. 4  On either side of the bridge of the nose. 5  Behind the nose directly in front of the brain.
An O-ring is a round ring that is used as a gasket for sealing a connection. O-rings are typically constructed out of polyurethane, silicone, neoprene, nitrile rubber or fluorocarbon. These rings are commonly used in mechanical applications, such as pipe connections, and help to ensure a tight seal between two objects. O-rings are designed to be seated in a groove or housing that keeps the ring in place. Once in its track, the ring is compressed between the two pieces and, in turn, creates a strong seal where they meet.
Make sure there are no rips or tears and that the O-ring is not dried out or cracked. A damaged O-ring can draw air into the torch body, contaminating the weld zone with oxygen. If your torch has a gas valve, check the O-ring at the stem there as well. A new O-ring costs about a dollar. Take a look at the gaskets on the top and bottom of the torch.