### Question
What does class I substance mean?


### Answer
**Class I substance** has the following meaning in *42 U.S.C. § 7671*:

> each of the substances listed as provided in section 7671a(a) of this title

#### Citation:
  - *42 U.S.C. § 7671*
  - Heading: **SUBCHAPTER I-PROGRAMS AND ACTIVITIES > Subchapter Referred to in Other Sections**

