Does A Window Air Conditioner Pull Air From Outside?

Summer is fast approaching, and temperatures are on the rise. You have probably started running your air conditioner. The way window units are designed, you may be wondering if they pull air from the outside. We were wondering the same thing and did some research on the matter. You'll find the results below.

Window air conditioners do not pull air from the outside. Instead, they draw air from inside the home and circulate it around the house. You are probably wondering why part of the unit hangs outside. This is because the excess hot air from inside is deposited outside through an exhaust system, leaving cold air in its place. 

Now that you know your window air conditioner does not pull polluted air from the outside keep reading for more information on window units, including how the fan mode differs from the cooling mode, how it provides fresh air, and more.

A window air conditioning unit outside an apartment building, Does A Window Air Conditioner Pull Air From Outside?

Does a Window Air Conditioner Pull Air from Outside?

When you think about the dirty air that your window unit may pull from the outside, it may make you change your mind about turning on your air conditioner. You can put those worries to the side because window air conditioners do not pull polluted air from outside. Instead, it circulates air from inside your home and dumps the excess hot air outside.

A window air conditioning unit photographed outside a weathered shingle siding house

Do Window Air Conditioners Circulate Air?

Window air conditioners do circulate air. That is actually their purpose; however, according to O.C. McDonald Company, the air is not circulated from outside the home. The unit pulls hot air from the room and uses a compressor to turn the hot air into cold air, trapping dirt and debris in the filter. If the filter is not clean, the air the AC pushes out will not be as cold.

Does a Window AC Provide Fresh Air?

Your AC does not provide fresh, outdoor air for your home. However, this does not mean that it does not provide fresh air. The window unit contains an air filter. Contrary to popular belief, the filter does not remove toxins from the outside air. Instead, it filters dust and debris, such as pet hair, from indoor air before circulating it back into your home. That way, you are breathing cooler, cleaner air.

Many times, indoor air can be more polluted than outdoor air, depending on where you reside. The air inside can get stale and dirty without proper circulation and filtration. If you are concerned about pollutants, it may be time to look at your air conditioner's filter.

You can purchase different types of filters for your window unit. Most window air conditioners come equipped with Minimum Efficiency Reporting Value filters, which can only filter large particles. These basic filters eliminate dust and pet dander, but you may need a more specialized filter to get rid of pollen and other allergens. Look for a High-Efficiency Particulate Air Filter for better filtration within your home. It gets rid of the tiniest particles in the air.

Is it Important to Keep the Filter Clean?

If you have a window air conditioner, you have probably heard that it's essential to keep the filter clean. Some people swear by keeping them clean, while others let the filters get dirty before they bother washing them. The truth is, filters cannot do their job if they are clogged with dirt.

Think about it this way - Imagine you have a bowl underneath a leaky faucet. The bowl is catching the water as it leaks out. What happens when the bowl is full? Do you leave it and let the sink continue to drip, causing the bowl to overflow? Of course not!

The same logic applies to filters. If the filter is packed with dust and grime, how can it catch additional particles from the air? As it builds up, it will eventually begin spitting the dirt back into your home. Therefore, it's essential to keep your filters clean, allowing them to catch as many pollutants as possible without dispersing them back into your house.

A dirty filter will make it difficult for the unit to work correctly. The air conditioner will have to work harder to circulate and clean the air, causing electric bills to rise. Additionally, your AC won't be able to catch extra allergens in the room, so that you will be breathing them all into your lungs.

Should a Window AC Vent be Opened or Closed?

Have you noticed the vent on your air conditioner? You are probably wondering what it does. When it's opened, the vent allows air from the outside to be pushed inside. Likewise, the inside air is pushed outside. Why would you want your inside air to go out?

In most cases, you will want to keep the vent closed. However, the vent can be useful if the air inside your home becomes too dry. It can also be helpful if the air inside your house gets too stale or polluted. You can open the vent on your air conditioner to circulate the bad air out, replacing it with fresh air from outside. One example of when this would be useful is outlined below:

Imagine you are cooking a meal for your family. You forget about the stove and burn the food. The house is filled with smoke, everyone is coughing, and the smoke alarm is going crazy. Instead of standing there with a piece of paper fanning the smoke detector, you can open the vent on your window unit. This will push the smoky air out of the house and pull clean air from outside.

Most of the time, however, the vent should remain closed. If all the cold air is getting pushed outside and replaced with hot air, your air conditioner will have to work extra hard to keep the house cool. This can cause your unit to overheat if the vent remains open for too long and can also cause your light bill to increase.

What is the Fan Mode on a Window AC Unit?

Have you ever used the fan mode on your AC? It works much like a regular fan. When fan mode is on, your air conditioner does not create cold air. It only circulates the air that is already in the room. The air won't get any cooler; you will get a nice breeze. If the air is hotter inside the house than outside, this would be an excellent time to use the vent, circulating the cooler air from outside and pushing the hotter air out of the room.Dirt accumulated by the air conditioning unit


Many people worry that window air conditioners may be pulling dirty air from outside and circulating it within the house. You may not realize it, but your home is filled with dirt, debris, and allergens. If not properly ventilated and filtered, the air within the home is dirtier than the air on the outside, which is circulated regularly by wind and other elements.

That being said, the window unit does not pull air from the outside. Instead, it uses existing air from inside the home and circulates it around the room once it has been cooled. It's essential to keep the filter clean to ensure the AC is working correctly and trapping allergens from the air. For more information on window air conditioner units, such as why it may be freezing up or if running a ceiling fan will help the AC work better, check out these other posts on our blog.

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