What is a common requirement for all class licenses under the boiler operation regulations?

The correct answer is based on the necessity for documentation as specified in the regulations governing boiler operation licenses. All class licenses, including Second Class, require applicants to provide particular types of documentation, which may include proof of education and training, as well as verification of experience in the field. This formal documentation serves to ensure that individuals have met the mandatory qualifications and competencies to operate boilers safely and effectively.

This focus on documentation aligns with regulatory standards aimed at maintaining safety in boiler operations, emphasizing the importance of verified training and knowledge in handling boiler systems. While other aspects, such as examinations or on-site training hours may be relevant, the common thread across all class licenses emphasizes adhering to documentation standards as a foundational requirement.