For the purpose of this subpart:

(a) Except as provided in paragraphs (b) and (c) of this section, the general definitions, abbreviations, and methods of analysis set forth in 40 CFR part 401 and §430.01 of this part shall apply to this subpart.

(b) Cotton fiber furnish subdivision mills are those mills where significant quantities of cotton fibers (equal to or greater than 4 percent of the total product) are used in the production of fine papers.

(c) Wood fiber furnish subdivision mills are those mills where cotton fibers are not used in the production of fine papers.