Various radioactive materials of limited quantity, low specific activity (LSA), and surface contamination on objects (SCO), are exempt from the usual Type A and Type B packaging requirements by 49 CFR 173.403 and IAEA regulations. Curie levels and computed Type A quantities for such materials can be substantial; however, they are irrelevant because the materials are transported under special rules.

Other radioactive materials that do not exceed a Type A quantity must be packaged in a Type A packaging.

Materials that exceed a Type A quantity and are not exempt as per the first paragraph must be packaged in a Type B packaging.

Transport by air of certain special radioactive materials requires a Type C packaging.