Chimneys and vents shall have airspace clearance to combustibles in accordance with this code and the chimney or vent manufacturer’s installation instructions.
Exception: Masonry chimneys equipped with a chimney lining system tested and listed for installation in chimneys in contact with combustibles in accordance with UL 1777, and installed in accordance with the manufacturer’s instructions, shall not be required to have a clearance between combustible materials and exterior surfaces of the masonry chimney. Noncombustible firestopping shall be provided in accordance with this code.
Two or more listed and labeled appliances connected to a common natural draft venting system shall comply with the following requirements:
Appliances that are connected to common venting systems shall be located on the same floor of the dwelling.
Exception: Engineered systems as provided for in Section G2427.
- Inlets to common venting systems shall be offset such that no portion of an inlet is opposite another inlet.
- Connectors serving appliances operating under a natural draft shall not be connected to any portion of a mechanical draft system operating under positive pressure.
Connectors for oil and solid fuel-burning appliances shall be constructed of factory-built chimney material, Type L vent material or single-wall metal pipe having resistance to corrosion and heat and thickness not less than that of galvanized steel as specified in Table M1803.2.
TABLE M1803.2
THICKNESS FOR SINGLE-WALL METAL PIPE CONNECTORS
| DIAMETER OF CONNECTOR (inches) | GALVANIZED SHEET METAL GAGE NUMBER | MINIMUM THICKNESS (inch) |
| Less than 6 | 26 | 0.019 |
| 6 to 10 | 24 | 0.024 |
| Over 10 through 16 | 22 | 0.029 |
For SI: 1 inch = 25.4 mm.
A chimney connector or vent connector shall not pass through any floor or ceiling. A chimney connector or vent connector shall not pass through a wall or partition unless the connector is listed and labeled for wall pass-through, or is routed through a device listed and labeled for wall pass-through and is installed in accordance with the conditions of its listing and label. Connectors for oil-fired appliances listed and labeled for Type L vents, passing through walls or partitions shall be in accordance with the following:
- Type L vent material for oil appliances shall be installed with not less than listed and labeled clearances to combustible material.
- Single-wall metal pipe shall be guarded by a ventilated metal thimble not less than 4 inches (102 mm) larger in diameter than the vent connector. A minimum 6 inches (152 mm) of clearance shall be maintained between the thimble and combustibles.
A connector shall not be smaller than the flue collar of the appliance.
Exception: Where installed in accordance with the appliance manufacturer’s instructions.
Connectors shall be installed with clearance to combustibles as set forth in Table M1803.3.4. Reduced clearances to combustible materials shall be in accordance with Table M1306.2 and Figure M1306.1.
TABLE M1803.3.4
CHIMNEY AND VENT CONNECTOR CLEARANCES TO COMBUSTIBLE MATERIALSa
| TYPE OF CONNECTOR | MINIMUM CLEARANCE (inches) |
| Single-wall metal pipe connectors: | |
| Oil and solid-fuel appliances | 18 |
| Oil appliances listed for use with Type L vents | 9 |
| Type L vent piping connectors: | |
| Oil and solid-fuel appliances | 9 |
| Oil appliances listed for use with Type L vents | 3b |
For SI: 1 inch = 25.4 mm.
- These minimum clearances apply to unlisted single-wall chimney and vent connectors. Reduction of required clearances is permitted as in Table M1306.2.
- Where listed Type L vent piping is used, the clearance shall be in accordance with the vent listing.
Appliances shall be provided with a listed and labeled venting system as set forth in Table M1804.1.
TABLE M1804.1
VENT SELECTION CHART
| VENT TYPES | APPLIANCE TYPES |
| Type L oil vents | Oil-burning appliances listed and labeled for venting with Type L vents |
| Pellet vents | Pellet fuel-burning appliances listed and labeled for use with pellet vents |
Mechanical draft systems shall comply with UL 378 and shall be installed in accordance with their listing, the manufacturer’s instructions and, except for direct-vent appliances, the following requirements:
- The vent terminal shall be located not less than 3 feet (914 mm) above a forced air inlet located within 10 feet (3048 mm).
- The vent terminal shall be located not less than 4 feet (1219 mm) below, 4 feet (1219 mm) horizontally from, or 1 foot (305 mm) above any door, window or gravity air inlet into a dwelling.
- The vent termination point shall be located not closer than 3 feet (914 mm) to an interior corner formed by two walls perpendicular to each other.
- The bottom of the vent terminal shall be located not less than 12 inches (305 mm) above finished ground level.
- The vent termination shall not be mounted directly above or within 3 feet (914 mm) horizontally of an oil tank vent or gas meter.
- Power exhauster terminations shall be located not less than 10 feet (3048 mm) from lot lines and adjacent buildings.
- The discharge shall be directed away from the building.
The effective area of a natural draft chimney flue for one appliance shall be not less than the area of the connector to the appliance. The area of chimney flues connected to more than one appliance shall be not less than the area of the largest connector plus 50 percent of the areas of additional chimney connectors.
Exception: Chimney flues serving oil-fired appliances sized in accordance with NFPA 31.