N.Y.C. Admin. Code § FGC 634: Section FGC 634: Chimney Damper Opening Area

634.1 Free opening area of chimney dampers.

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 634.1 Free 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)

a

8

13

20

29

39

51

64

Appliance Input Rating (BTU Per Hour)

6

7,800

14,000

23,200

34,000

46,400

62,400

8,000

8

8,400

15,200

25,200

37,000

50,400

68,000

86,000

10

9,000

16,800

27,600

40,400

55,800

74,400

96,400

15

9,800

18,200

30,200

44,600

62,400

84,000

108,800

20

10,600

20,200

32,600

50,400

68,400

94,000

122,200

30

11,200

21,600

36,600

55,200

76,800

105,800

138,600

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.