Let’s explore the three most common code violations in the HVAC industry — and how to address them. Dryer Vent System ComponentsThis mainly concerns transition ducts and backdraft dampers. Transition ducts must fully comply with UL 2158A and be properly labeled and listed. Dryer Vent MaterialBecause dryer vents expel heated gases and may accumulate combustible deposits that pose a fire risk, the material must be robust and fire-resistant. Therefore, it is best to install metal ducts initially and insulate them from the outside using properly rated insulation if needed.