During sanitary welding, it is important to maintain a sterile environment to prevent corrosion from occurring or contaminants from entering the system being welded. Purge plugs are typically made of materials such as Duravar-Ultra High Molecular Polyethylene or PTFE and are designed to fit tightly into the opening being welded. This creates a seal at the ends of the workpiece where purge gas displaced oxygen. This means the welding process can occur without the introduction of outside contaminants.