scope:

This document describes the specification requirements for air, including atmospheric air, and air synthesized by blending oxygen and nitrogen in the proper proportions. It is different from other gas specifications because atmospheric air is not a manufactured product but is naturally occurring. Atmospheric air contains a large variety of trace constituents. It is impractical to set individual limits for many of these. However, this specification qualifies certain grades of air by limiting the concentrations of specific trace constituents.

The Directory of Limiting Characteristics, Table 1, contains significant modifications from the quality verification levels (QVLs), i.e., grades, shown in the 1973 edition. All references should be to the current edition of ANSI/CGA G-7.1, Commodity Specification for Air.