TL;DR
A combustion air opening is the louver, grille, or duct inlet sized by code to feed outside or interior air to fuel-burning appliances in a confined space. The traditional rule for openings to outdoors is one square inch of free area per 4,000 BTU of appliance input when direct, with two openings, one high and one low, to promote circulation.
What it means
A combustion air opening is the louver, grille, or duct inlet sized by code to feed outside or interior air to fuel-burning appliances in a confined space. The traditional rule for openings to outdoors is one square inch of free area per 4,000 BTU of appliance input when direct, with two openings, one high and one low, to promote circulation. During inspections these get flagged when someone has blocked them to stop drafts, a fix that quietly sets up backdrafting and CO problems.
Where it sits in the glossary
Combustion air opening is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
This is a term Ohio homeowners encounter when reading contractor quotes, hiring paperwork, or inspection reports. Understanding it well enough to ask one good follow-up question is usually all the protection a homeowner needs.
ProFix Directory keeps definitions short on the index page and saves the longer context — Ohio-specific rules, where the term comes from, and which ProFix tools touch it — for these per-term pages so the term is easy to cite and easy to share.
ProFix tools that touch this term
See also
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