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

1. Permit System: Employers must develop a written permit space program that includes procedures for safe entry, testing, monitoring, and emergency response. The permit must specify the space to be entered, purpose, duration, authorized entrants, and hazards [1].

2. Hazard Evaluation: Before entry, the employer must evaluate the space to identify hazards, including atmospheric hazards, and ensure that conditions are safe for entry [2].

3. Atmospheric Testing: The atmosphere within the space must be tested for oxygen content, flammable gases, and toxic substances. Continuous monitoring is required if conditions can change [3].

4. Ventilation: If a hazardous atmosphere is detected, the space must be ventilated to eliminate the hazard before entry. Continuous forced air ventilation may be used to maintain safe conditions [3].

5. Training: Employees must be trained to understand the hazards, use equipment properly, and perform their duties safely. This includes training for entrants, attendants, and supervisors [1].

6. Rescue and Emergency Services: Employers must have procedures for summoning rescue services and provide necessary rescue equipment. A retrieval system should be in place for non-entry rescue [2].

7. Communication: Effective communication must be maintained between entrants and attendants to ensure safety during entry operations [1].

8. Isolation and Control: Measures must be taken to isolate the space and control hazards, such as lockout/tagout procedures and purging or inerting the space [1].

These requirements are designed to protect workers from the unique hazards associated with confined spaces, ensuring their safety during entry and work operations.