N.Y.C. Admin. Code § 27-893: § 27-893 Clearances.

(a) Minimum clearance. Minimum clearances at vent connectors to combustible materials shall not be less than those listed in table 15-10.

(b) Reduced clearances. These clearances may be reduced when the combustible construction is protected as provided in table 15-11.

TABLE 15-10 Vent Connector Clearance for Gas-Fired Equipment

Equipment

Minimum Distances from Combustible Materials (in.)

Type B Gas Vent Material

Other Than Type B Materials

Boiler

As required by Std.

6

Warm air furnace

As required by Std.

6

Water heater

As required by Std.

6

Room heater

As required by Std.

6

Floor furnace

As required by Std.

6

Conversion burner (with draft hood)

6

9

Equipment with draft hoods

6

9

Equipment without draft hoods

Not Permitted

18

TABLE 15-11 Reduced Clearances for Vent Connectors with Specified Forms of Protection a

Specified Form of Protection b 

Reduced Clearances Where the Required Clearance with No Protection is:

18 in.

9 in.

6 in.

(a) 1/4 in. asbestos millboard spaced out 1 in.c 

12

6

3

(b) 28 gauge sheet metal on 1/4 in. asbestos millboard

12

4

2

(c) 28 gauge sheet metal spaced out 1 in.c 

9

4

2

(d) 28 gauge sheet metal on 1/8 in. asbestos millboard spaced out 1 in.c 

9

4

2

(e) 1 1/2 in. asbestos cement covering on heating appliance

18

9

6

(f) 1/4 in. asbestos millboard on 1 in. mineral fiber bats reinforced with wire mesh or equivalent

6

4

2

(g) 22 gauge sheet metal on 1 in. mineral fiber bats reinforced with wire or equivalent

3

2

2

(h) 1/4 in. asbestos cement board or 1/4 in. asbestos millboard

18

9

4

(i) 1/4 in. cellular asbestos

18

9

3

Notes for Table 15-11:

a Except for the protection described in (e) above, all clearances should be measured from the outer surface of the appliance to the combustible material disregarding any intervening protection applied to the combustible material.

b Applied to the combustible material unless otherwise specified and covering all surfaces within the distance specified as the required clearance with no protection. Thicknesses are minimum.

c Spacers shall be on noncombustible material.