634.1 Free opening area of chimney dampers.
FGC § 634.1
Where an unlisted decorative appliance for installation in a vented fireplace is installed, the fireplace damper shall have a permanent free opening equal to or greater than specified in Table 634.1. Table 634.1Free Opening Area of Chimney Damper for Venting Flue Gasses from Unlisted Decorative Appliances for Installation in Vented Fireplaces Chimney Height(Feet)Minimum Permanent Free Opening (Square Inches) a8132029395164Appliance Input Rating (BTU Per Hour)Chimney Height(Feet)Minimum Permanent Free Opening (Square Inches) a8132029395164Appliance Input Rating (BTU Per Hour)67,80014,00023,20034,00046,40062,4008,00088,40015,20025,20037,00050,40068,00086,000109,00016,80027,60040,40055,80074,40096,400159,80018,20030,20044,60062,40084,000108,8002010,60020,20032,60050,40068,40094,000122,2003011,20021,60036,60055,20076,800105,800138,600 For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 square inch = 645.16 m 2 , 1 British thermal unit per hour = 0.2931 W. a. The first six minimum permanent free openings (8 to 51 square inches) correspond approximately to the cross-sectional areas of chimneys having diameters of 3 through 8 inches, respectively. The 64-square-inch opening corresponds to the cross-sectional area of standard 8-inch by 8-inch chimney tile.
