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 Permit: 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. The training should ensure they understand the hazards and the procedures to follow [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. This includes ensuring that rescue services are available and that they are capable of performing rescues [5].

7. Reevaluation and Reclassification: If conditions change, the space must be reevaluated and, if necessary, reclassified. A permit space can be reclassified as a non-permit space if all hazards are eliminated [6].

These requirements are designed to protect workers from the significant risks associated with confined spaces, ensuring that all necessary precautions are taken before and during entry.