MSHA - Code of Federal Regulations - 30 CFR 33.31
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MSHA - Title 30 CFR
30 CFR § 33.31
Test space.

(a) Drilling tests shall be conducted in a test space formed by two curtains suspended across a mine opening in such a manner that the volume of the test space shall be approximately 2,000 cubic feet.

(b) No mechanical ventilation shall be provided in the test space during a drilling test, except such air movement as may be induced by operation of drilling or dust-collecting equipment.

(c) All parts of a unit or system shall be within the test space during a drilling test.