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- Venting of Gas Appliances (UPC 509–510 / IFGC 501–504) — vent types, chimneys, terminations, connectors, draft hoods, sizing rules
Venting of Gas Appliances Both Codes Agree On — Which Appliances Are Vented, Types of Venting Systems, Chimneys, Gas Vents and Terminations, Single-Wall Pipe, Through-the-Wall Terminals, Vent Connectors, Draft Hoods and Dampers, and the Category I Sizing Rules (UPC 509–510 / IFGC 501–504)
A gas water heater, furnace or boiler is not finished until its flue gases have a lawful way out. The rules for that come from NFPA 54 (the National Fuel Gas Code): the 2018 UPC prints them as 509 (Venting of Appliances) and 510 (Sizing of Category I Venting Systems), and the 2018 IFGC prints the same text as 503 (Venting of Appliances) and 504 (Sizing), with IFGC 501–502 adding general chimney and vent-listing rules. Texas adopts both code families (22 TAC 367.2), so an item here is true under either book. The section numbers differ; the words do not. Learn the rules by picture — *what may ve
2018 UPC and 2018 IPC · Reviewed 2026-09-20
1. Every appliance vents outdoors — except the short list
- Every appliance discharges its products of combustion to the outdoors through a venting system that satisfies the appliance's draft requirements (UPC 509.2, 509.3; IFGC 501.2, 503.3).
- Appliances not required to be vented (UPC 509.2.1; IFGC 501.8): ranges; built-in domestic cooking units listed for optional venting; hot plates and laundry stoves; Type 1 clothes dryers (exhausted per the dryer rules instead); a single booster-type instantaneous water heater serving only a dishwasher's sanitizing rinse in a commercial kitchen with mechanical exhaust; refrigerators; counter appliances; room heaters listed for unvented use; direct-fired makeup air heaters; other appliances listed for unvented use without flue collars; limited-input specialties such as laboratory burners and gas lights.
- The 20 Btu/h rule: where the unvented items (booster heaters through specialties) add up to more than 20 Btu/h per cubic foot of room volume, enough of them are vented to bring the unvented total back under 20 Btu/h per cubic foot; an adjoining room joined by a permanent opening counts toward the volume (UPC 509.2.2, 509.2.3; IFGC 501.8).
- Ventilating hoods and exhaust systems may serve as the "vent" only for industrial appliances and commercial applications (UPC 509.2.4; IFGC 503.2.1); industrial appliances in a large, well-venti
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