OSHA's requirements for confined space entry are detailed in the standard 29 CFR 1910.146, which outlines the practices and procedures to protect employees from the hazards of entry into permit-required confined spaces. Key requirements include:

1. Permit-Required Confined Spaces: Employers must identify and evaluate the workplace to determine if any spaces are permit-required confined spaces. These spaces must be clearly marked with signs indicating the danger and the requirement for a permit to enter [1].

2. Permit Space Program: Employers must develop and implement a written permit space program that includes measures to prevent unauthorized entry, identify and evaluate hazards, and establish procedures for safe entry operations. This program must specify acceptable entry conditions and provide for the use of appropriate personal protective equipment and emergency equipment [2].

3. Entry Permits: Before entry, a permit must be issued that includes details such as the purpose of entry, the duration of the permit, the names of authorized entrants, and the hazards present. The permit must also outline the measures taken to isolate the space and control hazards [3].

4. Training: Employers must provide training to ensure that all employees involved in confined space entry understand the hazards and the procedures for safe entry and work. This includes training for attendants and entry supervisors [3].

5. Atmospheric Testing: The atmosphere within the confined space must be tested for oxygen content, flammable gases and vapors, and toxic air contaminants before entry and periodically during the entry to ensure safe conditions are maintained [4].

6. Rescue and Emergency Services: Employers must have procedures in place for summoning rescue and emergency services and must provide the necessary equipment for safe rescue operations. This includes ensuring that rescue personnel are trained and equipped to perform rescues from confined spaces [5].

7. Communication and Monitoring: Continuous communication must be maintained between entrants and attendants, and the space must be monitored for any changes in conditions that could pose a risk to entrants [6].

These requirements are designed to ensure the safety of workers entering confined spaces by addressing potential hazards and establishing clear procedures for safe entry and work.