Combustion Air Vent

Combustion Air Vent – what you don’t know, or do can kill you!

From the desk of Paladin Home Inspection


As a Stillwater home inspector, I know that a lot of homeowners are confused by some of the components of their home.

One item I lookout for is a dirty combustion air vent.

A combustion air vent is a passive one, which means that it doesn’t have a fan. It supplies air to the furnace room. Gas-fired appliances like the furnace and water heater need oxygen to burn the fuel for proper combustion.

How much air / oxygen and what size Combustion Vent does your home require?

Okay, here’s the math your furnace installer used to compute size of the duc work.

Combustion Air Vent math

But if the vent on the side of the house is dirty, air can’t get in. If the furnace room runs out of air, a slight vacuum is created. That could lead to exhaust from the furnace and water heater to “backdraft”, or spill exhaust into the house instead of outside of it. You probably know that high levels of moisture and CO are bad for your health. What you may not know is that the solution is extremely easy; clean the vent. With gloved hand or  shop vac  clean vent screen on the outside of the building at least once a year.

Look out for wasps.

That’s it.

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