What tables in the B149.1 Code are used to size air supply to an enclosure or structure that has an equivalent leakage area of 0.05 m2 at a differential of 10 Pa?

• A. Table 7.1 - outdoor air controls for airtight enclosures.
• B. Table 8.1 - appliances having draft control or Table 8.2 - appliances not having draft control.
• C. Table 9.1 - sizing of flue gas vents.
• D. Table 6.5 - minimum clearance for draft hood.

Answer: (B)

Combustion air supply for an enclosure is determined by whether the appliances inside have draft control. The code uses the enclosure’s equivalent leakage area measured at a differential (like 10 Pa) to estimate outdoor air needs, but the specific sizing tables depend on the draft‑control status of the appliances.

If the appliances have draft control, use the table designated for appliances having draft control to size the outdoor air supply. If the appliances do not have draft control, use the table designated for appliances not having draft control. The other tables in the code handle different topics—such as general outdoor air controls, sizing of flue vents, or minimum draft-hood clearances—and do not directly provide the air‑supply sizing based on the leakage and differential for appliances with or without draft control.

So, the correct approach is to reference the tables that correspond to whether the appliances in the enclosure have draft control or not, which is why the applicable choice is the one listing Tables for appliances having draft control and appliances not having draft control.