Can Flies Come Through an Air Conditioner?

A window-mounted air conditioner can keep your home cool and comfortable, but it can also introduce its own problems. If you fail to properly install and seal the air conditioner in the window, you could be letting outside pests such as flies and other insects into your home.

Unless there is a hole in the air conditioner or the filter, the flies probably are not coming in through the unit itself. But those flies could be coming in through the sides of the air conditioner, especially if you do not have a tight fit. Window air conditioners ship with flexible sides to accommodate a number of different window sizes. Over time, those sides can crack, allowing air -- and flies -- to enter your home.

The best way to keep flies from entering your home through the air conditioner is to seal the sides of the unit as tightly as possible. Begin by checking the sides of the unit for cracks or holes. If those cracks or holes are small, you can seal them with duct tape or a sealing kit from the manufacturer of the air conditioner. If the sides are severely damaged, they should be replaced with new ones.

Flies can get into your home around the air conditioner, even if the sides of the unit are free of cracks and holes. If you fail to make a tight seal between the sides of the air conditioner and the window, that gap can allow flies and other insects to enter your home. You can seal any gaps between the window and the sides of the air conditioner with duct tape or with special sealant tape from the hardware store.

It is difficult to tell where the flies in your house are coming from. Those files could have entered your home when you opened the door, or they could be getting in through holes and gaps in screens or seals around the windows. If you suspect the air conditioner is to blame, the easiest way to test is with fly stickers. Hang a fly sticker on each side of the air conditioner by taping the top of the sticker to the window. If you see a large collection of flies on those window-hung stickers, you can be fairly certain they are coming in through the air conditioner.