In many situations, certification of non-hazardous atmosphere by a trained or competent person is required before personnel may enter a confined space without the use of a respirator. In the United States Navy, that person is the designated shipboard gas-free engineer. Certification in civilian settings can be performed by an Entry Supervisor who, under O.S.H.A. regulations is designated by the employer and ensures that the space is safe to enter and all hazards are controlled.

In the United States, agricultural and construction operations are exempted from regulations governing permit-required confined spaces (which is specific to general industry), but they are still required to identify and control confined space hazards.