Which statement best describes the rule for manually operated dampers?

• A. Must be installed on all residential appliances.
• B. Shall only be used if necessary, be provided with a permanent fixed opening, and not be installed in on a residential appliance.
• C. May be installed in any appliance.
• D. Should be used even when not necessary.

Answer: (B)

Manually operated dampers are intended to control, not block, the flow of combustion and vent air. They should only be used if there’s a definite need to reduce or tailor draft, and when they are used, there must be a permanent fixed opening that provides a continuous path for air to enter or escape. This ensures the appliance always has adequate combustion air regardless of the damper position. Installing a damper on a residential appliance is avoided because homes typically rely on natural air exchange, and a damper could be left closed or fail, leading to poor combustion, CO buildup, or backdraft into the living space. So the rule emphasizes using dampers only when necessary, guaranteeing a permanent air opening, and not placing dampers on residential appliances.