This addendum classifies air with respect to contaminant and odor intensity and limits the recirculation of lower-quality air into spaces that contain air of higher quality. It adds two tables and an additional column in the existing Table 2. These tables classify air from a variety of space types and in some specific airstreams. The classifications are based on contaminant concentration and odor intensity. For locations that are not listed in the tables, the air classification of the listed space or airstream that is most similar in terms of occupant activities and building construction must be used. To aid this determination, the classification criteria that were used by the committee are provided in a note (to Section 5.x.1) in the addendum.