Sizing Guide

Venting Guidelines for Category I Gas Appliances

Single-Appliance Vent - Tables 1 and 2 (continued)

10. Vent connectors shall not be upsized more than two sizes greater than the listed appliance

categorized vent diameter, flue collar diameter, or draft hood outlet diameter.

11. In a single run of vent or vent connector, more than one diameter and type shall be permitted to be

used, provided that all the sizes and types are permitted by the tables.

12. Interpolation shall be permitted in calculating capacities for vent dimensions that fall between table

entries. (See Example 3.)

13. Extrapolation beyond the table entries shall not be permitted.

For SI units, 1 inch = 25.4 mm; 1 foot = 0.305 m; 1000 Btu/hour = 0.293 kW; 1 inch

= 645 mm

14. For vent heights lower than 6 feet and higher than shown in the tables, engineering methods shall be

used to calculate vent capacities.