CFR /  Title 30  /  Part 75  /  Sec. 75.400-1 Definitions.

(a) The term coal dust means particles of coal that can pass a No. 20 sieve.

(b) The term float coal dust means the coal dust consisting of particles of coal that can pass a No. 200 sieve.

(c) The term loose coal means coal fragments larger in size than coal dust.