Nitrogen is produced in large quantities at air separation plants which liquefy and subsequently distill air into nitrogen, oxygen and argon. If very high purity nitrogen is required the nitrogen produced may need to go through a secondary purification process. The lower range of Nitrogen purities can also be produced with membrane techniques, and medium to high purities with pressure swing adsorption (PSA) techniques. Nitrogen is used for inserting finished medicinal products sensitive to degradation by Oxygen. Compressed Nitrogen is a preferred source for driving of surgical tools.