Which of the following containers is exempt from the requirement for labeling?

The scenario of pipe and portable in-house containers intended for immediate use is correctly identified as exempt from the requirement for labeling due to their specific context of use. When hazardous substances are contained within pipes or portable containers that employees are using on-site, the hazard is generally already communicated through training and the established operational protocols. The understanding is that these items are typically used in direct, controlled environments where employees are familiar with the materials and their associated hazards, reducing the necessity for additional labeling as a safety precaution.

In contrast, other containers mentioned, such as those used for storage in warehouses, are often not monitored continuously, making labeling crucial for safe handling and awareness of contents until the material is used. Pesticide containers on retail shelves require labeling to inform consumers of the risks associated with the product, while containers for shipping hazardous materials must always be labeled to ensure safe transport and compliance with regulations. Therefore, the unique conditions surrounding pipe and portable containers intended for immediate use justify their exemption from standard labeling requirements.