A Guide On How To Install A Combustion Air Vent 

Combustion appliances have become an essential part of our lives. We use boilers, gas-fired furnaces, wood stoves, fireplaces, water heaters, kerosene/natural gas heaters, small propane heaters, and any other fuel-burning appliances in our homes. These appliances produce heat and combustion gases as they burn.

The combustion by-products (smoke and invisible gases) produced by these appliances is why many homes have vent pipes and chimneys. However, outlets for combustion gases to leave aren’t enough. We need inlets to replace the removed air.

The replacement of the removed air may be challenging because many modern homes are built like cookie jars, airtight. So, there is little or no room for fresh air to come into the houses. But combustion air vents solve this problem by allowing fresh air from outside to replace the removed air inside.

This post discusses how you install combustion air vents in your homes, why every house needs one, and the problems that come with them.

How To Install A Combustion Air Vent 

Different companies have combustion air vents that are reliable and durable. These air vents help in continuing the combustion cycle without harming human health.

You may need to install a combustion air vent for the parts of your house with combustion appliances.

Here is a guide to installing combustion vents in your fireplace:

Step#1: Purchase a combustion air vent: 

You can order directly from the manufacturer or buy from a hardware store. But make sure you research about the brand before splashing the cash.

Combustion air vents have improved over time. Many modern combustion air vents allow you to control how much air goes in through the vents. You can also increase or reduce it by turning the air vents left or right.

Step#2: Create an opening in your fireplace:

If you don’t already have a vent hole in your fireplace, you need to make a hole. The bottom of the hole must be about 4 inches away from the floor of the fireplace. The spot can be in the sidewall or at the center of the fireplace.

Step#3: Mount the purchased combustion air vents:

Mount the vents horizontally in the hole of the sidewall or the center of the fireplace.

Step#4: Seal the joints: 

Use furnace cement to seal the joints providing a full bed of refractory motors in and around the vent. Ensure that the joint between the duct, flange, and fireplace wall is adequately sealed.

Step#5: Extend the air vents: 

You would have to extend your air vents from your fireplace to an outside wall. To do this, you need to attach your installed air vent to a 4 inches galvanized pipe that runs from the fireplace to an outdoor wall.

Remember to maintain a 1-inch minimum clearance for any combustible construction carried out in your home.

Step#6: Cover the galvanized pipe with a louver: 

Use a louver to cover the mouth of the pipe from outside. The job of the louver is to prevent anything (aside from the air) from going in through the tube—for example, bugs, birds, and small animals.

What Is A Combustion Air Vent? 

Combustion air vents are single holes installed, usually, next to the furnace, to bring fresh air from outside into the house. These vents are necessary because many homes get sealed up tight to prevent air leakage. So, outdoor air must come in from a controlled source.

Essentially, every house should have a combustion air vent. It is a building code requirement. Therefore, contractors and engineers can seal the entire place to avoid air leaks, but they must add this single hole that allows air to come into the house. An adequately installed combustion air pipe would keep the house from getting depressurized.

Importance Of Combustion Air Vents 

The primary importance of combustion air vents is that it introduces fresh air into the house. However, the fact is many household items remove air from your house.

The common ones are boilers, furnaces, water heaters, etc. Others include cloth dryers, kitchen and bathroom exhaust fans, wood-burning fireplaces, etc.

Having all these appliances means, air is constantly leaving the house, which is necessary to avoid pollution. The removed air gets replaced through the air vents for the combustion cycle to continue.

Combustion would be impossible without fresh air coming into the house through the combustion air vents.

Combustion Air Vents Do’s And Don’ts 

You can use your combustion air vents for a long time without issues if you adhere to some simple rules. Here are some of them:

Please do not block the air vents:

Blocking the air vents defeats the purpose of installing them in the first place. People block their air vents because cold air comes in through them. They stuff the vents with items that prevent air from getting into the house.

Don’t do this. Remove any blockage from your combustion air vents. If you’re using modern combustion air vents, you might be able to increase or decrease the amount of air coming into your house.

Also, people who use combustion air ducts deal with the cold by trapping the air. You can try this. To do this, place a box or bucket at the bottom of the duct.

The air coming into the house through the vent will enter the container first and then rise. This method might not be 100% effective, but it supposedly makes the rising air less cold.

Clean the air vents:

The pipe outside your house connecting to the combustion air vents close to your fireplace needs cleaning.

The air that passes through the tube may come with dust, insects, dirt, or leaves. Usually, the closer the outer pipe is to the ground, the more likely it is to get blocked by debris from outside.

You can clean your outer pipes at least once every year by vacuuming. Be careful while looking under the vents to avoid a wasp attack. The cleaner you vent is the less debris that will enter your house.

Don’t use window screens for the exterior:

The best material for the exterior pipes is materials that have holes that are not less than ¼”. Do not use window screens or anything with holes that are more than ½” because they would give room for more dirt to enter your house.

Don’t install the air inlet too close to the ground:

The pipe installed from outside should be at least 12 inches above the ground. Installing the pipe too close to the ground would cause it to get blocked easily by dirt or snow.

In cases where the pipe is already close to the ground, you can use a “snorkel” to make the hole appear higher than it is.

Combustion Air Vents And Combustion Spillage 

As combustion appliances burn fuel, heat and combustion gases escape through vent pipes or the chimney. However, some may escape into the house, which can cause serious harm to your health, especially with how airtight some homes are.

The unwanted spread of combustion gases in your house is called combustion spillage. These spills are often in small quantities, but there are rare occasions where large combustion spills happen in homes.

Combustion gases often contain toxic compounds that can lead to various health issues, from minor illnesses like headaches to death. These health issues are why we must remove combustion gases without leaks and introduce fresh air through combustion air vents.

Some of the toxic compounds in combustion gases include carbon monoxide, Unburnt hydrocarbons, carbon dioxide, water vapor (not particularly harmful but can cause water problems in the house), Nitrogen and sulfur oxides, Aldehydes, soot, Polycyclic aromatic hydrocarbons, etc.

The composition of the combustion gases released in your house is dependent on many different factors. Amongst them are the type of fuel your appliances burn, how the appliances burn the fuel, the type of venting system your house uses, and the overall state of your heating system.

The effect these gases have on your house and its occupant is dependent on the gases released, how much fresh air is coming in through the combustion air vents, and how the air circulates.

Combustion Air Vents And Chimneys 

Every house needs an inlet and an outlet. The combustion vents are inlets, while chimneys are outlets. The two channels work independently of each other to provide a conducive and healthy environment in your home.

Chimneys remove combustion gases from your house. To get the best out of your chimney, ensure it is properly installed, designed, and well maintained. A well-functioning chimney would adequately handle the removal of combustion gases from your house.


Combustion air vents should be a part of every home. The reason people have them in their homes is to maintain good health and keep the air in the home clean and fresh.

This post gives an overview of combustion air vents, their significance and how to maintain them.

You can also follow the steps provided to install the combustion vent in your home. Don’t bother about not having the technical skill. You can install the combustion air vent by following the guide provided in this post.

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I have always been a shopaholic. A lot of times my questions went unanswered when it came to retail questions, so I started Talk Radio News. - Caitlyn Johnson

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