G2407.5 (304.5) Indoor Combustion Air
Where the air infiltration rate of a structure is known, the minimum required volume shall be determined as follows:
For appliances other than fan-assisted, calculate volume using Equation 24-1.
For fan-assisted appliances, calculate volume using Equation 24-2.
For purposes of this calculation, an infiltration rate greater than 0.60 ACH shall not be used in Equations 24-1 and 24-2.