42 CFR § 84.51
Entry and escape, or escape only; classification
June 11, 2020
Respirators described in subparts H through L of this part shall be classified for use as follows:
(a) Entry and escape. Respirators designed and approved for use during entry into a hazardous atmosphere, and for escape from a hazardous atmosphere; or
(b) Escape only. Respirators designed and approved for use only during escape from a hazardous atmosphere.