Requirements for which of the following should be included in the written program?

Including requirements for labels and other forms of warning in the written program is essential because proper labeling is a key aspect of hazard communication. It ensures that all personnel are informed about the hazardous materials they may encounter in the workplace. Labels serve to effectively communicate the hazards associated with substances, thereby facilitating safety measures and emergency responses. Without clear labeling, employees may be unaware of the risks, which could lead to accidents or exposure to harmful substances.

The other options, while they may have their own relevance in specific scenarios, do not operate at the same level of critical importance as labels and warnings in a HAZWOPER context. For instance, listing machine brands or employee phone numbers does not directly contribute to safety regarding hazardous waste handling. Similarly, knowledge of languages spoken on site may be beneficial for communication purposes, but it does not address the immediate need for hazard communication through proper labeling and warning systems. Ensuring that the workplace is comprehensively trained and informed about hazardous materials through appropriate labels is a fundamental part of maintaining safety standards in hazardous waste operations.