Use of third party electrical equipment and materials

Electrical equipment and materials are available, either listed or labeled, or unlisted and unlabeled. Can unlisted and unlabeled equipment and materials be used for fabrication and installations? This paper examines consensus standards and the Code of Federal Regulations 29 to answer this question. The author merges text from the consensus standards with the Code of Federal Regulations 29 and reviews how the texts apply. The principle result is the clear understanding that third party listed or labeled equipment and materials shall be used in all cases unless the manufacturer of the equipment or material provides a safety letter.