OSHA has said that when any part of the body of an entrant breaks the plane of the opening of a permit-required confined space (PRCS) large enough to allow full entry, entry is considered to have occurred and a permit is required, regardless of whether there is an intent to fully enter the space. If a part of the body were placed in an opening through which the worker could not pass into the permit-required confined space, no PRCS entry will have occurred.
See the October 18, 1995, OSHA Letter of Interpretation for more information.