Can Bugs Get in Through Window Air Conditioner? Genius Tips to Prevent This

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With summer temperatures rising, window air conditioners are a welcome reprieve for many homeowners.

But some may notice unexpected and unwelcome guests coming in through the AC unit – bugs! It’s common to wonder, can bugs get in through window air conditioners? The answer is not so straightforward.

While window units do not provide an entry point for all types of pests, some bugs are skilled at finding even the smallest openings to exploit.

In this article, we will examine why insects are drawn to window air conditioning units, discuss what you can do to clean bugs out if they get inside, and most importantly, share tips to proactively prevent bugs from entering through a window-mounted AC.

By understanding the causes and solutions for bugs coming through air conditioner units, you can enjoy cool air this summer without the added company of insects.

Can Bugs Get in Through Window Air Conditioner?

The answer is yes, bugs can sometimes find their way into homes through window-mounted air conditioning units.

Window ACs are not completely sealed off from outdoor environments, so there are small openings that certain bugs are able to use to get inside.

While window air conditioners do not allow entry for larger pests like rodents, some flying and crawling insects, spiders, centipedes, and lizards are small enough to exploit any tiny gaps in the unit.

Their bodies are built to be able to fold up and fit into the smallest of spaces.

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Why Are Bugs Coming Through My Air Conditioner?

There are a few key reasons why you may notice bugs seeming to come into your home through a window-mounted air conditioning unit.

Bugs Are Drawn To the Cooler Air

  • On hot days, the air blowing out of the AC provides a desirable place for insects to congregate.
  • Upon finding gaps or openings, they may follow the airflow into your home without even realizing it.

Bugs Attracted To Light End Up Near the AC

  • Many flying insects gravitate toward light sources, so porch lights near your window AC at night are a beacon.
  • Once nearby, they may find their way inside through small gaps.

Bugs Look for Water Sources

  • Some small bugs like ants and spiders may be able to detect condensation build-up on air conditioning units.
  • Seeking it out as a water source and then slipping through the cracks.

Bugs Seek Shelter and Get Trapped

  • Some bugs accidentally find their way into window ACs while seeking shelter from rain, wind, or hot sunshine.
  • Once inside, they get stuck and end up in your home when the unit turns on.

Bugs Look for Food Sources

  • A few bugs like pantry moths may be attracted to the smell of food from your kitchen near the window AC and get inside the unit to reach the source.
The main motivation is that window air conditioning units provide a desirable location that draws bugs either intentionally or accidentally. 

This inevitably leads to some clever bugs finding a way to exploit gaps and get into your home through these openings.
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How Do Bugs Come Through AC Systems?

While window air conditioners do not have large, open passageways for pests, bugs can find subtle ways to exploit the small openings and gaps that exist in window AC units.

Here are some of the main potential entry points.

  • Cracks or gaps around the side panels and front grilles.
    • Even slight separation between panels and grilles can allow narrow passage for certain bugs.
  • Spaces in accordion side panels.
    • The folded pleats in expandable side panels can create small gaps that bugs crawl through.
  • Openings in back housing.
    • The exterior casing that houses the AC unit often has cracks that give bugs access from outside.
  • Condensation drainage holes.
    • Some water condensation drips out through small holes at the base, which bugs can also squeeze through.
  • Ductwork connections.
    • Where ducts connect from the AC to the window frame, incomplete sealing can allow bugs to find their way in.
  • Damaged seals/weather stripping.
    • Any compromised or degrading seals around panels create openings that bugs can exploit.

While these access points seem insignificant to us, many crawling insects are experts at folding their bodies up tight and fitting through the smallest of spaces to get inside.

So over time, they are inevitably able to find and take advantage of any marginal gaps in window AC units.

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What Kind of Bugs That Come Through the AC Unit?

Window air conditioning units do not provide an entry point for all types of pests. But certain bugs are small enough to exploit the slight gaps and openings in window ACs in order to get inside your home.

Here are some of the insects that are most likely to find their way through cracks in the air conditioner.

can bugs get in through window air conditioner


  • They may be drawn to light near the unit or to moisture and condensation that builds up inside.
  • A few flies that make it into the interior may lay eggs, allowing flies to breed and multiply over time.
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  • Foraging bees and wasps focused on collecting pollen, nectar or food sources can inadvertently follow cooling airflow coming from the AC unit into a home.
  • They are able to fit through tiny cracks and crevices.
  • Bees and wasps that end up inside may become trapped and confused while attempting to find a way out.


  • Blood-feeding female mosquitos have an innate ability to navigate through narrow openings and slits using their slender bodies.
  • They can fly into window AC units through tiny gaps seeking humans or animals nearby to bite.
  • Mosquitos can get trapped inside while trying to reach their hosts.
can bugs get in through window air conditioner


  • Common household spiders like cellar spiders, wolf spiders, and house spiders have the ability to crawl through amazingly small spaces.
  • This allows them to squeeze through tiny openings in window air conditioners, seeking cooler and darker areas to build webs and lay eggs.
  • Spider populations inside AC units can multiply in a pest-friendly environment.
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  • Foraging worker ants search extensively for food and can follow pheromone trails that lead them into AC units through minute exterior gaps.
  • Once one ant finds a way in, others will follow rapidly. Ant colonies may even form nests inside if conditions allow it.


  • Cockroaches are experts at folding their flat bodies to fit through unbelievably small cracks and crevices.
  • This allows them to squeeze through tiny gaps in window air conditioning units to gain access inside homes.
  • Roaches are attracted to the warm, humid environment inside most AC systems. Once inside, they can breed rapidly in these conditions.


  • This allows them to maneuver through even the smallest openings in AC units to get inside.
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In addition to insects that may fly or crawl into an AC unit from outside, there are some tiny bugs that can actually take up residence and thrive inside air conditioning systems over time. 

Dust mites and fleas in particular can flourish inside the dark, warm environment within AC units. 

Can Bed Bugs Come Through a Window Air Conditioner?

While not impossible, it is relatively uncommon for bed bugs to find their way into homes by coming through window air conditioning units.

Bed bugs prefer to live very close to human hosts, as they feed solely on blood.

So while they can survive inside AC systems, ductwork, and vents, they don’t typically travel far from human prey.

That said, the dark, enclosed spaces inside air conditioners can provide harborage for bed bugs seeking refuge.

In rare cases, bed bugs may use AC systems as a means of transport to move closer to humans from an infested area.

And if an AC unit itself becomes heavily infested, a few bed bugs could potentially squeeze out through exterior cracks.

But in general, smooth surfaces like window ACs are difficult for them to traverse. The tiny gaps that allow ingress for some insects are often too narrow for adult bed bugs, given their flat, oval-shaped bodies that span about 1/4 inch.

Fully sealing all openings provides additional protection against the off-chance of bed bugs entering through this unconventional route.

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How Do I Clean Bugs Out of My Air Conditioner?

If you’ve noticed bugs blowing into your home from your window AC unit, it’s definitely time for a deep cleaning to clear them out.

Here are some tips I’ve picked up for effectively removing pests

  • First things first – unplug the AC and remove any panels to access the full interior. Have someone help move heavy units. Safety comes first!

  • Once open, use a soft brush attachment on your vacuum to thoroughly clean out debris or visible bugs.
How to Clean A Window Air Conditioner (Kendall Todd TheSilverGuy)

  • Check the drain pan for standing water or grime that can breed bugs.
  • Dump out any water and use a bleach solution to sanitize the pan and kill larvae.
  • Let it fully dry before replacing.

  • Wipe down all the fins, coils, fan blades, and surfaces with antimicrobial cleaner or rubbing alcohol.
  • This disinfects and removes any remaining organic matter or eggs.
Once fully cleaned, dried out, and sealed up, your AC unit will be back to providing fresh, pest-free cooling. 

Just be sure to replace filters regularly and keep exterior areas clean to prevent future issues. 
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How To Prevent Bugs From Coming Through Window Air Conditioners

Once bugs find their way into your window air conditioning unit, they can be tricky to fully remove. That’s why prevention is critical to maintaining a pest-free home.

Here are some handy methods to stop bugs at the source and prevent infestations.

How To Prevent Bugs From Coming Through Window Air Conditioners

Install Weather Stripping

  • The compressible foam presses up against panels to fill spaces and create a tight seal.
  • As seasons change, make sure the seal remains intact.

Use Silicone Caulk

  • Squirting a bit of clear silicone caulk in and around window AC frames dries to seal up cracks nicely.
  • The waterproof sealant prevents air and bugs from getting in.

Try Window Insulation Kits

  • For a more temporary solution, window insulation film kits help seal ACs for winter.
  • The thick plastic sheeting adheres to frames and adds an extra barrier against drafts or pests. Remove it when AC season returns.

Cover Openings with Cardboard

  • An easy DIY fix is taping cardboard pieces over side vents or other openings prone to letting bugs in.
  • Cut cardboard to size and use strong tape to create a smooth seal around the AC edges.
can bugs get in through window air conditioner

Plug Holes with Paper Towels

  • For narrow slits or holes, lightly stuffing paper towels into the openings can create a tight blockage.
  • Spray a bit of expanding foam into gaps for a more permanent plug.

Use a Protective AC Cover

  • Ensure the cover is secure with no entry or exit points for bugs.

Keep Surrounding Areas Clean

  • Make sure to regularly clean areas around the outdoor AC unit and eliminate any standing water.
  • Fix any leaks that allow puddles to form and drain condensation lines properly away from the unit.
  • Keep plants trimmed back and debris cleared away so bugs aren’t drawn to the space around the air conditioner.

Consider Moving the AC Unit

  • If you’ve tried sealing, cleaning, and bug-proofing your window air conditioner but still find insects persisting, it may be time to try a new location.
  • Certain areas like near vegetation or woodpiles naturally draw more bugs.
  • Move the AC to an alternate spot away from prime bug real estate, even if just testing for a season.
  • This relocation can make a big difference in reducing pest access through the unit.
  • Just be sure the electrical wiring safely reaches and new window frame fits the unit properly.
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Can I Spray Bug Spray In My Air Conditioner?

It’s understandable to think grabbing the can of bug spray can help eliminate any pests that have made their way into your air conditioning unit.

However, spraying insecticides directly into your AC is not the right solution.

While chemicals may kill bugs initially, they can actually damage your AC system over time.

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Bug spray residues end up circulating through the interior coils, fan blades, and other components. This can start corroding and degrading these parts, shortening the lifespan of your unit.

Spraying also poses safety concerns. Any chemical fumes released into your home through the AC could be hazardous to inhale for you and your family members. It’s best to avoid dispersing pesticides indoors.

Furthermore, most bug sprays only provide temporary relief. Their effectiveness starts diminishing within days as residues dissipate.

Any bugs hidden away in cracks or crevices likely won’t get reached by the spray, and can reemerge later.

Rather than using risky quick-fix insecticides, go with safer and more effective prevention methods.

Take time to properly seal up all AC openings so pests can’t get in at all. And do a thorough deep clean of the unit to remove any organic matter or bugs inside without chemicals.

Investing in sealing, cleaning, and maintenance keeps your air conditioner free of bugs for good – and keeps your home’s air fresh and healthy. Skipping the bug spray protects your family and your AC system.

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Final Thoughts

With summer heat on the rise, air conditioning provides welcome relief – as long as you don’t have unwelcome pests coming along for the ride.

As we’ve discussed, it is possible for insects and other bugs to find their way into homes through cracks and openings in window AC units.

Be proactive about sealing potential entry points around your AC unit using weather stripping, caulk, or other barrier materials.

Take time periodically to thoroughly clean out the interior and ensure no organic debris is accumulating.

Monitor outdoor areas around the AC and address any water leaks or other bug attractions.

And don’t hesitate to call in a professional if needed to fully eliminate an infestation.

While the occasional spider or fly slipping through can’t be avoided completely, you can hugely minimize insects creeping in through your air conditioner.

Stay vigilant, follow prevention best practices, and ensure your AC unit gets the care it needs.

With a few key steps, you can keep cooling comfortably – not itchingly – all season long.

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Can bugs fly in through your window air conditioner unit?

Flying insects like flies, mosquitos, bees, and wasps can follow air currents through cracks in window AC units. Their slender bodies fit through tight spaces.

Can mosquitoes come through window air conditioner?

Yes, mosquitos can fly into window ACs through narrow gaps if they detect humans/animals to bite inside.

Can spiders get in through air conditioner?

Yes, spiders can crawl through amazingly small spaces and gaps in window units.

Can fleas come through air conditioner?

Fleas are small enough to fit through tiny AC gaps in search of hosts to bite. An AC unit can also harbor flea eggs and larvae.

Can bed bugs hide in air conditioners?

While uncommon, bed bugs can potentially use AC systems to harbor and travel through cracks if heavily infested.

Can dust mites be in air conditioner?

Yes, AC interiors provide ideal humid, warm environments for dust mites to accumulate and breed.

Can cockroaches come in through the air conditioner?

Yes, roaches can flatten bodies to fit through incredibly narrow spaces to enter AC units.

Can I spray vinegar into my window air conditioner?

No, spraying any liquids can damage AC parts. Use wipes instead to clean.

How to stop bugs from coming through window air conditioner?

Seal all gaps, clean away debris/standing water, install covers when not in use.

Resources – (for further reading)

The University of Tennessee System – Managing Pests Around the Home

I'm Ernest M Noah, the founder of I have years of experience as an exterminator in Texas and Idaho, and I'm passionate about educating people on how to deal with pest problems effectively and safely.