OSHA's requirements for confined space entry are detailed in the 29 CFR 1910 standards. Key requirements include:

1. Permit-Required Confined Spaces: Employers must identify and evaluate confined spaces to determine if they are permit-required. A permit-required confined space has one or more of the following characteristics: a hazardous atmosphere, potential for engulfment, an internal configuration that could trap or asphyxiate, or any other recognized serious safety or health hazard [1].

2. Atmospheric Testing: Before entry, the internal atmosphere must be tested for oxygen content, flammable gases and vapors, and potential toxic air contaminants. Continuous monitoring is required to ensure safe conditions [2].

3. Ventilation: Continuous forced air ventilation must be used to eliminate any hazardous atmosphere before entry and must continue until all employees have left the space [2].

4. Entry Permits: A written entry permit must be issued before entry, detailing the hazards, measures taken to isolate the space, acceptable entry conditions, and the results of atmospheric tests [3].

5. Training and Roles: Employers must provide training to ensure employees understand the hazards and procedures. Specific roles such as authorized entrants, attendants, and entry supervisors must be designated and trained [4].

6. Emergency and Rescue Procedures: Employers must develop and implement procedures for summoning rescue and emergency services, and for rescuing entrants from permit spaces. Unauthorized personnel must be prevented from attempting a rescue [4].

7. Reclassification: A permit-required confined space can be reclassified as a non-permit space if all hazards are eliminated without entry into the space [5].

These requirements are designed to protect workers from the significant risks associated with confined spaces, ensuring that entry is conducted safely and that emergency procedures are in place should conditions change.