Regardless, all appliances must be connected to venting systems. The venting system must never extend into or pass through any fabricated air duct or furnace plenum. It must convey an adequate, positive flow of flue or vent gases directly to the outdoors.

Mechanical Draft Systems

Mechanical draft systems must be installed according to the manufacturer's recommendations and installation instructions.

The appliance can be mechanically drafted by either forced- or induced-draft methods.

Forced-draft systems and all portions of induced-draft systems must be under positive pressure during operation and must not leak into the building.

Natural-draft appliances must not have their vent connectors connected to any portion of a mechanical draft system that is operating under positive pressure.

The vent termination of a mechanical draft system must be at least 7 feet above ground level, and at least 3 feet above any forced-air inlet located within 10 feet. There are exceptions to this rule: The mechanical draft venting system can terminate at least 4 feet below, 4 feet horizontally from, or 1 foot above any door, operable window, or gravity air inlet into any building. The vent termination must be at least 1 foot above ground level.