27 CFR §21.110
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
Conforms to specifications as established by the American Society for Testing and Materials (ASTM) in the 1980 Annual Book of ASTM Standards, Part 23, page 229, Standard No. D 439-79. Any of the “seasonal and geographical” volatility classes for unleaded gasoline are considered suitable as a denaturant. (For incorporation by reference, see § 21.6(b).)