IMC · 2021 International Mechanical Code
§1007.1 · Combustion air
Effective in IMC 2021 · IMC 2024 SE Wisconsin · IMC 2024 NW Indiana.
Plain-English explainer
1007.1 requires fuel-burning appliances to have combustion air sized per the fuel and appliance category, drawn from outdoors or from a space large enough to supply the full input. The drafter cites it for any permit that adds a Category I vent or relocates a water heater to a basement or below-grade story.
Why inspectors flag this
A basement water heater without an outside combustion-air run is the canonical 1007.1 failure; the drafter lifts this rule so the contractor plans the duct before the rough-in.
As quoted in the code: Fuel-burning appliances get combustion air sized per the fuel and appliance category, drawn from outdoors or from a space large enough to supply the full input.
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