OSHA's requirements for confined space entry are detailed in the 29 CFR 1910.146 standard, which outlines the necessary precautions and procedures to ensure safety. 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 are maintained [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, entry conditions, and the measures taken to ensure safety. The permit must be available to all entrants [3].

5. Training and Roles: Employees must be trained for their specific roles, such as authorized entrants, attendants, and entry supervisors. Each role has specific duties to ensure safety during entry operations [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 of Spaces: A permit-required confined space can be reclassified as a non-permit space if all hazards are eliminated without entry into the space. Documentation of this reclassification must be maintained [5].

These requirements are designed to protect workers from the significant risks associated with confined spaces, such as hazardous atmospheres and physical hazards. Employers must ensure compliance with these standards to maintain a safe working environment.