30 CFR § 56.14107
Moving machine parts.
(a) Moving machine parts shall be guarded to protect persons from
contacting gears, sprockets, chains, drive, head, tail, and takeup pulleys,
flywheels, couplings, shafts, fan blades, and similar moving parts that can
cause injury.
(b) Guards shall not be required where the exposed moving parts are
at least seven feet away from walking or working surfaces.
For more information: See MSHA'S Program Policy Manual