OSHA's requirements for confined space entry are detailed in the 29 CFR 1910.146 standard, which outlines the necessary practices and procedures to protect employees from the hazards associated with confined spaces. Here are the key requirements:

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: contains or has the potential to contain a hazardous atmosphere, contains a material that has the potential to engulf an entrant, has an internal configuration that could trap or asphyxiate an entrant, or contains any other recognized serious safety or health hazard [1].

2. Entry Permit: Before entry, a written permit must be issued, detailing the space to be entered, the purpose of entry, the date and duration of the permit, authorized entrants, attendants, entry supervisors, hazards, and measures to control hazards [2].

3. Atmospheric Testing: The atmosphere within the space must be tested for oxygen content, flammable gases and vapors, and potential toxic air contaminants before entry. Continuous monitoring is required to ensure safe conditions are maintained [3].

4. 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 [3].

5. Training: Employers must provide training to ensure that all employees involved in confined space entry understand the hazards and the procedures necessary for safe entry and work [2].

6. Rescue and Emergency Services: Employers must develop and implement procedures for summoning rescue and emergency services, and for rescuing entrants from permit spaces [4].

7. Attendants: At least one attendant must be stationed outside the permit space for the duration of entry operations to monitor the safety of entrants and perform other duties as required [4].

8. 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 ensure that confined space entry is conducted safely and that all potential hazards are identified and controlled before and during entry.