Powered makeup air shall be provided if the size of a single opening or multiple openings exceeds _____ inch diameter or equivalent.

Powered makeup air shall be provided if the size of a single opening or multiple openings exceeds _____ inch diameter or equivalent.

• A. 11
• B. 7
• C. 10
• D. 9

Answer: (A)

Makeup air is required whenever the air leaving a space through exhaust openings could create negative pressure, by ensuring there is a controlled supply of outside air to balance the exhaust. The threshold used is the area of a circular opening 11 inches in diameter (about 95 square inches). If the combined area of all outdoor openings reaches or exceeds that size, a powered makeup air system must supply air to the space. The term “equivalent” means you can add up the areas of multiple openings to see if they total the same as an 11-inch opening. For example, several openings each around 7 inches in diameter collectively surpass the threshold, triggering the requirement. This helps prevent negative pressure and backdrafting, and it ensures comfort and proper operation of combustion appliances and ventilation.

Makeup air is required whenever the air leaving a space through exhaust openings could create negative pressure, by ensuring there is a controlled supply of outside air to balance the exhaust. The threshold used is the area of a circular opening 11 inches in diameter (about 95 square inches). If the combined area of all outdoor openings reaches or exceeds that size, a powered makeup air system must supply air to the space. The term “equivalent” means you can add up the areas of multiple openings to see if they total the same as an 11-inch opening. For example, several openings each around 7 inches in diameter collectively surpass the threshold, triggering the requirement. This helps prevent negative pressure and backdrafting, and it ensures comfort and proper operation of combustion appliances and ventilation.