According to IMC standards, what must appliances be in terms of safety?

The correct answer is that appliances must be listed and labeled according to IMC standards. This requirement ensures that the appliances meet certain safety and performance criteria as established by recognized testing organizations. Being listed and labeled means that the appliances have undergone comprehensive assessments to verify their compliance with applicable safety standards.

This labeling process provides assurance to installers, inspectors, and consumers that the equipment has been evaluated for safe operation, which is essential for minimizing hazards such as fires or carbon monoxide poisoning. The listing indicates that the appliance adheres to the necessary technical and safety regulations, giving confidence in its reliability and operational integrity.

While other options mention important considerations regarding regulations, approvals, and testing, they do not specifically represent the core requirement of appliances being recognized by a credible testing organization through the listing and labeling process. This focus on third-party verification is fundamental to ensuring overall safety in mechanical systems as outlined in the International Mechanical Code.