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Category I gas appliance: A gas fired appliance that operates with a non-positive vent static pressure and is labeled as a Category I appliance.

Category II gas appliance: A gas fired appliance that operates with a non-positive vent static pressure and is labeled as a Category II appliance.

Category III gas appliance: A gas fired appliance that operates with a positive vent static pressure and is labeled as a Category III appliance.

Category IV gas appliance: A gas fired appliance that operates with a positive vent static pressure and is labeled as a Category IV appliance.

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Direct vent appliance: Fuel fired appliances that are labeled as direct vent appliances and that are designed and installed to obtain combustion air directly from the outside atmosphere and to discharge the products of combustion directly to the outside atmosphere.

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Pellet fuel burning appliance: A closed combustion, vented appliance equipped with a fuel feed mechanism for burning processed pellets of solid fuel of a specified size and composition.

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M-1204.1 Vent application: The application of vents shall be in accordance with Table M-1204.1.

Table M-1204.1
Vent Applications

M-1204.[1] 2 Approval: All vent systems shall bear the label of an approved agency. Type B and BW vents shall be tested in accordance with UL 441. Type L vents and pellet vents shall be tested in accordance with UL 641.

M-1204.[2] 3 Connection and size: Appliances shall be approved for connection to a vent system.

M-1204.[3] 4 Installation: Vent systems shall be sized, installed and terminated in accordance with the vent and appliance manufacturer's installation instructions.

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M-1204.4.3 Insulation shielding: Where vent systems pass through insulation materials, an insulation shield shall be provided to maintain the required clearance between the vent and the insulation material. In attic and similar spaces, the insulation shield shall extend to a point not less than 4 inches above the level of the insulation material.

M-1204.4.4 Outdoor protection: That portion of a vent system that is located outdoors below the edge or eave of the roof shall be enclosed in a weather-tight chase.

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M-1206.1 Foundations: Masonry chimneys shall be supported on approved noncombustible foundations. [The supports shall be independent of the building construction and the load shall be transferred to the ground.]

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M-1206.8 Gas fired appliances: Masonry chimneys utilized to vent gas-fired appliances shall be located, constructed and sized as specified in the manufacturer's installation instructions of the appliances being vented.

M-1206.9 Lining systems: Except as provided in Sections M-1207.2, M-1208.2 and M-1209.2, chimney lining systems designed for installation in new or existing masonry chimneys shall bear the label of an approved agency and shall be installed in accordance with the manufacturer's installation instructions.

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M-1214.4 Size of chimney or vent: The chimney or vent shall be sized to vent all connected appliances. Appliances connecting on different floor levels shall be sized by approved vent tables. Multiple connections involving Category I gas-fired appliances without draft hoods shall be sized in accordance with the appliance and with the chimney or vent manufacturers installation instructions.
M-1214.4.1 Alternative area method: For multiple connections other than those involving Category I gas appliances without draft hoods, [T] the minimum area of the chimney or vent shall be equal to the area of the largest appliance connection plus 50 percent of the area of each additional appliance connection.

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M-1215.2 Connections to exhauster: All appliance connections to a chimney or vent equipped with a power exhauster shall be made on the inlet side of the exhauster. All joints on the positive pressure side of the exhauster shall be sealed to prevent flue gas leakage as specified in the manufacturer's installation instructions for the exhauster.

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M-1216.3.6 Location: Connectors shall be located entirely within the room in which the connecting appliance is located except as [permitted] provided for in Section M-1216.3.4.1. Chimney and vent connectors installed in unconditioned spaces including attics, crawl spaces and garages shall not be constructed of single-wall pipe.

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Table M-1216.3.7
Connectors Clearances To Combustibles

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