These requirements cover nonducted, stationary or fixed heat recovery ventilators for household, commercial, or industrial use and intended to be employed in accordance with the National Electrical Code, NFPA 70.

These requirements cover heat recovery ventilators rated 600 volts or less.

These requ irements cover heat recovery ventilators that may be mounted through a wall or ceiling, or in a window.

These requirements cover heat recovery ventilators that may employ sh ort ducts intended to bring air to and from the equipment . These requirements do not cover heat recovery ventilators employing ducts intended to suppl y conditioned air for environmental heating and/or cooling or distribute air throughout a building; such units are judged under the requirements in the St andard for Ducted Heat Recovery Ventilators, UL 1812. These requirements do not preclude a preheater provided as part of the air exchange system.

A product that contains features, characteristics, components, materials, or systems new or different from those in use when the Standard was developed, and that involves a risk of fire, electric shock, or injury to persons, shall be evaluated using the appropriate additional component and end-product requirements as determined necessary to mai ntain the level of safety for the user of the product as originally anticipated by the intent of this Standard.