What type of heat recovery ventilators must be listed and labeled according to specific standards?

Heat recovery ventilators (HRVs) play a crucial role in improving indoor air quality by exchanging stale indoor air with fresh outdoor air while retaining energy. The correct choice highlights nonducted heat recovery ventilators, which must adhere to specific standards for safety and performance. These devices are typically used in applications where ductwork may not be feasible or where simplicity is desired for installation and operation.

Nonducted HRVs often rely on specific listing and labeling by recognized testing laboratories, ensuring that they meet the necessary requirements for energy efficiency and operational efficacy. This helps to assure end users and builders that the products used in residential or commercial settings are compliant with industry standards and provide reliable performance.

In contrast, ducted, portable, and exhaust units may have different requirements or can function under various specifications, and may not necessitate the same rigorous standards as nonducted HRVs when it comes to listing and labeling. Understanding these distinctions is essential for compliance with the North Carolina Mechanical Code and ensuring safety and performance in ventilation systems.