How to treat your air vents for bugs

What do you do when you’re chasing a spider or a roach only to have it escape into an air vent? If you douse the opening with Raid or poof some boric acid dust into it guess what will be coming out in about 10 minutes when the air kicks on. That’s right, you’ll either have the smell of your aerosol and or any airborne pesticide particles floating around your living area and this sometimes can go on for days. This is not good and for obvious reasons you should ALWAYS avoid spraying anything into air vents or air returns.

I’m often asked to spray in air vents but my usual reply is; “Sure, I can do that and when I’m done can I spray in your fish tank?” Of course the answer is always NO and a look of puzzled concern always follows. I explain that both actions are about the same because I’m putting pesticide in a place where you cannot avoid breathing it and I have no control of where it goes. Just as your fish will surely take ill it would be no less irresponsible for me to treat your vents in this way.

Can vents be treated?

The short answer is yes but your options are sort of limited. The best way is to simply remove the vent and place a fold up glue trap inside the vent. Since roaches and spiders can easily walk around the trap there is no guarantee you’ll catch them and while baiting with a smear of peanut butter might entice the roach it will give your home that nice aroma of a 3 day old school lunch sack. Maybe you want to think about that. You could spray around the vent but drywall sucks up liquids and it’s doubtful any residual would be on the surface in enough of an amount to provide a lethal dose. Plus you still may get airborne chemicals when the heat or or a/c turns on. Some vents are vertical and it is difficult place a trap inside, for these types what I sometimes do is place wide strips of clear packing tape over the vent leaving thin slits (1/4 to 1/2 inch wide) so that the air can still come through but when the insect tries to crawl out to freedom he will get stuck and die. Packing tape is great because you can still see into the vent and it usually comes off cleanly whereas masking or duct tape won’t.

Can bugs live in vents & do they come in from them?

Almost all bugs are sensitive to air currents in one way or another and roaches will actually avoid the air from a fan. To much direct forced air will begin to dehydrate the bug and if they do spend some time in a vent it won’t be long before they start looking to get out. As far as spiders or bugs entering your living areas from the vents, it’s not likely unless you have a break or tear in one of the ducts. In one case I treated a home that had fleas only in a tub and not all the time. After being man looking into vent pestcemetery.compuzzled for awhile the a/c kicked in and I suddenly had fleas on my shoulders and head. The air vent above the tub was kicking them out every time the air went on and upon further inspection we found a birds nest in a large tear of the flexible air tubing in the attic. The nest was removed, attic treated, the duct fixed and the clear tape trick got the rest. What happens most concerning vents and pest entry is that the vent itself is not sealed tightly up to the ceiling. Critters in the attic follow the air current, see the light or detect food odors through the opening and the slip through right next to the vent. This gives the illusion that they are in the vent which is almost never the case. While I may dust into the void to block them I most often suggest sealing up the opening.

These same rules apply anytime you are using pesticides and would include car vents, box fans, window a/c units or anything that will return your spray back to you in an uncontrolled way. If you think creatively you can get around the use of residual sprays in these areas and still get rid of your pest. You just need to think outside the vent.

About The Bug Doctor

Jerry Schappert is a certified pest control operator and Associate Certified Entomologist with over two and a half decades of experience from birds to termites and everything in between. He started as a route technician and worked his way up to commercial/national accounts representative. Always learning in his craft he is familiar with rural pest services and big city control techniques. Jerry has owned and operated a successful pest control company since 1993 in Ocala,Florida. While his knowledge and practical application has benefitted his community Jerry wanted to impart his wisdom on a broader scale to help many more. was born from that idea in 2007 and has been well received. It is the goal of this site to inform you with his keen insights and safely guide you through your pest control treatment needs.

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  • PJ

    Hi, We moved into a home in Northern Virginia just 11 months ago. We have had an infestation of something or other for nearly eight months now. We had an air duct in the attic that was separated from the trunk line and when we had a duct cleaning company come to clean vents, they must have disconnected some more vents in the attic. That, plus we have a dog who likes to be outside and ended up with Lyme’s Disease from ticks. After the duct cleaning we noticed dirt blowing out of our vents. We wonder if this started the infestation. Didn’t know there was a duct separation until we had a new HVAC system put in and the technician saw it and sealed it.
    Since then we’ve had a new roof, a total attic clean out with new insulation and we are still having problems. We are at our wits end. We have an exterminator coming and still a problem What are we to do?

  • First step is to ID the made the right call getting a qualified person to come out to either find out what it is or rule out any type of pest… Once you know–THEN you can move forward with what to do

  • Scott

    I’m having the same issue, but I don’t have it anywhere else. I put up fly lights and Fly paper to trick and catch one of these, but I can’t see to get it. And as noted above, the Pest Control Professionals won’t apply anything because they can’t see anything.

    I’ll spray and aresoal for flying bugs and get relief for 2-3 days, before they come back. I’ve washed everything in hot soapy water and dried on hot hot heat. How can I get rid of these bugs?

  • Mariestallings

    Help! My 15 yr old daughter has not been able to sleep in her room due to the ridiculous spiders that have decided to come out at night! We live in Los Angeles and it has been over 100 degrees here lately. They are medium size black spiders and some are thin brown spiders. They are on her walls and the problem might be the water bottles from her guinea pig cages. ( I read your article about spiders being attracted to water. ) or the aloe Vera plant? But I just bought brand new miracle gro and I know there were no spiders in the bag. She has two other plants and I replanted those the same day too. I doubt it’s the plants but your the expert. what can we do? We keep only dry food in the GP cage and we feed lettuce during the day and it’s all finished, nothing left in the cage. What can I do? Also, the hallway right outside her room has an attic entrance. It looks like the sealing has a tight fit with the opening but I think spiders could squeeze through. Please give me any other solutions, this has become a nightmare. She finds 3-5 each night. I use peppermint oil and I doubled the amount of the oil, pls tell me what I am doing wrong.

  • Theresa

    I recently have discovered roaches since I have acquired neighbors with numerous cats. I have a house that is over 100+ years old. My air vents are on the floor. I noticed a roach going into the air vent the other day. How can I ensure that while treating the house for roaches that I am not overlooking the ventilation system? Since the vents are on the floor is there something I should be doing? I had an exterminator out several weeks ago, but he only treated my kitchen. Now I see them everywhere and I think the problem is bigger than I originally thought. I need help. My house is clean and after 4 years of living here I have never had roaches and now I don’t even want to come home! What do I do???

  • Linda

    It’s been four years now battling springtails. Unfortunately I am sensitive to them and they have plaqued me everywhere. We’ve had our home treated inside and out for over three years, but if I don’t vacuum and wipe the floors every other day, I suffer. We’ve caulked around the house, sprayed insulation on the cellar ceiling, epoxied the floor of the garage. You name it and I still notice them upstairs. Here’s my question. Could they be coming in from the ceiling heating/AC vents?
    The downstairs is a tough call because we bring them in from outside, but upstairs we don’t even bring our clothes is the bedroom unless they are just out of the wash. It’s been hell dealing with them. When they spring off of me I react like I’ve been bitten due to my allergies. I’ve lost countless night’s sleep. Im up for any and all suggestions.

  • Michael Hatch

    I’ve been having multiple insect issues in my 3rd floor apartment, which my landlords insist are simply because I live in a district of the city surrounded by garbage cans and restaurants. In short, their reaction was “deal with it.”

    I frequently find house flies buzzing around, but eventually they just drop dead on one
    of the windowsills. I sprayed the windowsills with bug barrier liquid, but that was months ago, now. It’s the oddest thing, like sometimes I’ll see them on the windowsill, squirming around and actively dying. I also find tiny mosquito-looking bugs on top of my air conditioners, also dead.

    The one that grosses me out the most, though, Is the bathroom. I find dead gnats all over my bathroom floor, every morning. I see the occasional live one buzzing elsewhere around the apartment. I know they’re bugs, and bugs happen, but I should not be sweeping them up every morning.

    Again, my landlords’ reaction was essentially “deal with it.”

    What can I do?

  • Get the critters ID’d first then that may give you a clue to a fix

  • I doubt highly you’re “brining them in” not in any great numbers if any….. Have you had them positively ID’d?

  • Linda

    Yes, by an exterminator. Our home is in a very rural area. It had been empty for a couple of years. When we tore the carpets up we found nests. Since I’ve written the last post, I put a filter over the vents and found almost nothing but I find them on the window sills. We truly were infested. We had the exterminator (several) spray indoors with Telstar inside and out but it was affecting me and my husband. We stopped and I now wash my floors( no more carpeting) with a solution of vinegar/water and Dawn dishwashing liquid. It helped greatly. The amounts I find now are mostly in the basement and damper areas.
    If I didn’t have such a sensitivity I probably would barely notice. It’s only happened since I moved here five years ago. Believe me, to someone with allergies, it’s an awful trial.
    Thank you for your answer!


  • Alexis Schmidt

    Hi I live in San Marcos, TX and right now we are literally plagued with crickets. I live in a town home and my room is on the first floor. I have had a cricket infestation for a week and I have witnessed from different areas that they are all coming through the ventilation. I have asked my management about it and they said its because the AC thing outside isn’t correctly sealed and thats how they are getting in and they put in a pest control order for them to spray for crickets. I am not entirely confident that they did the job (the maintenance here isn’t too reliable) and would like to have other options to do it myself. I have covered the only vents I can in my room by sealing them with plastic trash bags and duct tape mostly because one of the vents is above my bed and when I am in my bed crickets fall onto me so I have been sleeping on the couch before I did this. The bug man came today and apparently said that after spraying there would be some bug activity but there were almost none showing up yesterday before he came and after he comes there are more showing up but they are more lively than before. Could that possibly be the poison doing its thing? Or should I just spray around myself because he did a sloppy job?

  • Krystal Clark

    I’m moving into a house that has a flea problem. I have no clue how bad the infestation is because it was there before we moved in. My dad, who used to be a maintainence man for an apartment complex, told me to place a Fogger or two in front of an air duct/vent, and then clean them out afterwards. But I have no clue how to do that and I don’t believe I should because I’ll be having a child soon and I don’t want him breathing in toxic chemicals. Any suggestions on what to do? I really want these fleas gone before my son is born, I don’t want him being a blood buffet for any fleas whatsoever.

  • Don L

    I had this before. Fleas tend to stay in one area and hitch rides to travel. They need cover to breed like carpet or inside a couch. Treat your pets then the carpet and uphoulstry. At night, put a bowl full of water below a nightlight in several areas around the house. Fleas love to jump in those bowls. Once the bowls are empty in the mornings, your flea problem is gone.

  • Pamela Feather

    I have had a diagnosis from my pest company that I have drain flies in our house. They seem to collect under the house in the crawlspace and creep into the house via cracks. To make a very long story short, I have explored every every option. Leaks, drains, under house issues, windows cleaned of any moist matter. NO LUCK. Finally yesterday I had my heater serviced, as I do yearly, and the technician said on my report that there is a nest of flies in my heaters return plenum. I know drain flies need silt or sludge and moisture, so this seems strange. Have you ever heard of this happening before from a heater plenum?

  • They just need a small amount of gelatinous material- no matter where it is.

  • TC

    Hi Linda! I concluded with the same question, i have the same problem as you and havent found a solution.. since two months ago i have been dealing with thid and my life had never been the same.. Please help if you have found gelp, pkease share any advice.. blessings..

  • Linda

    It’s been a battle, but I found out what works for me. Firstly, I feel your agony. If you have rugs throughout your home, you’ll have to vacuum frequently. Mine were so bad I took all the rugs out. Be VERY sure to seal any openings on the outside of your home. (Around your doors and windows too). We waited too long to do this and it took us forever to stop them from coming inside. A dehumidifier is a must.

    Storm doors helped. If you have wood or tile floors using a solution of a gallon of water to a cup of vinegar and just a few drops of Dawn dishwashing liquid kills them! I wipe up the water residue. Be careful it may ruin your floors. I did this every couple of days for two weeks to kill them.

    Keeping your home dry is a must. Now here is something I had to do about my clothing. Fleece is a no no. They cling to it. Even after you wash it!! I refuse to buy it now. A hot dryer kills them. Even with all of that PLUS exterminators it took months to keep down the population and I have an indoor cat. So he picks up anything on the floor.

    It’s been a nightmare for me because I react to these tiny bugs. Inside and out. I was given one great bit of advice. If they bother you in your bedroom, put a small fan to blow under your bed. It stops the moisture from building up. It helped me greatly.

    I wish you luck. One good thing about the vinegar, it won’t be toxic like the chemicals are. We had to stop them because it was affecting us!


  • Medavinci

    For two summers now, greenish-blue metallic flies have been coming out of a large AC vent near my bedrooms. They are so fast. They fly around the chandelier, a big window, the door moldings & the TV. They flew into my kitchen and other rooms. This past summer was horrific. Even baby yellow jackets got in (didn’t see them; they stung me as I went to kill the flies (I went into anaphylactic shock). It was complicated further bec I had fallen in the spring on a sidewalk and suffered a bad concussion, tore discs in my lower back, the meniscus in both knees, fractured my nose and broke teeth. The MRI also found a neck tumor/cancer. I couldn’t even walk up and down the stairs, and I literally just wanted to die seeing all these flies! I had the AC people check the attic where the unit is, but they didn’t find any dead animals. I don’t know if an animal could have gotten into the big vent itself, but when I finally called a pest control company, they didn’t look in the vent (said it wasn’t their job). They sprayed outside and put white powder on the windowsills but never told me. I have a dog who likes to look out the windows, so I was very upset. I found out when I saw white powder all over my furniture! They also left the sticky fly paper down on the floors open (which the supervisor told me should have been tented since I have a dog). I’ve been in my home 25yrs and it’s only been the past two summers I’ve had this infestation. I’m petrified of next summer already, and it’s only November. I can’t afford the pest control, bec I am unemployed and my home is in foreclosure. The company I used charged me $515 to come out one time, and without my permission started charging me an additional $42/mo (without providing any service, but I am fighting this now). I also have a child with a neurological disorder, and I don’t want her exposed to these metallic flies, as I read they carry disease. Is there some way to figure out if there is a dead animal in that vent? Since I have cancer and all these injuries, I don’t know what to do nor can I reach the vent even if I was well. I feel like the flies are living in and lurking in the vent just waiting to break out again as soon as summer comes… Any help would be appreciated. P.S. I was told by the pest control company to spray the flies with hairspray if more came out after they sprayed outside. It does work but now my windows are sticky & destroyed. I’m so stressed over this.

  • cajunkitty

    do they get into ur sinuses

  • Linda

    I know they go anywhere to find moistness. I have had them in my nose, I hope they havent gone further!

  • Linda

    TC. Be sure to find out if your home is completely sealed outside, try to tape or block any openings. Vacuum daily and use white vinegar on surfaces that allow you to do so. It can be mixed in a solution of one cup vinegar to one half gallon of water with just a couple drops if Dawn dish washing liquid. I spray it on my floor and wipe off the residue. I only find them now in places like closets but they are lessening. Having the house treated was worthless!
    Be aware they can stick to fleece clothing. Even the wash doesn’t remove them! I won’t buy fleece anymore. Wearing cotton helped greatly. Good luck!

  • GregZBernard

    Advion from Dupont works wonders at eliminating roaches and is available on Amazon. They do not seem to come back or if they do they are dying out-of-sight before they cause a plague. Hit the end of every joist in the basement (where the wood joists/beams meet the edge of the house). Those corners are where you need to hit with the Advion gel and you will be fine in a couple of days. Don’t even bother with Earth-Friendly crap. That doesn’t do crap for roaches. Forget anything containing natural clover or cinnamon or whatever. The chemicals in real stuff are synthetic versions of these plants that actually will kill the roaches. I spray a bunch of eucalyptus or something earth friendly spray on a roach and I had a nice smelling roach that probably made a few thousand nice smelling babies later that night.

    Dirty-ness does not cause roaches and it will not stop roaches once they take a liking to your place. They need water so check that the drains on your kitchen sink are not dripping at all. Also, make sure the shower is sealed and no water is getting behind the tub or the walls due to loose caulk or grout. Check where the tub meets the floor on the outside of the tub as well. If you have a toilet and you think it is leaking try converting to a polyurethane wax ring. Polyurethane will expand and contract to keep a seal between the toilet and the floor. With actual wax for a toilet seal you create gaps between the toilet and the floor (actually, the toilet flange) every time the toilet rocks and that is where the critters like to go for water. Saniseal is an awesome wax ring that is sold in hardware stores.

    Fleas need an insect growth regulator as the babies become full-grown, biting,nasty, disease-carriers in 2 weeks. The IGR (insect growth regulator) prevents the adults from having babies or something like that. The other chemical actually kills the fleas. One IGR is destroyed by sunlight. Nylar is one type of IGR. You will have to look up about these as they use several names.

    Bedbugs. Do not throw away a bed. You will still have bugs. That is a good lie that the mattress companies probably made up. Let’s call these things bed bugs so people throw out perfectly fine mattresses and still have bugs. You should wrap the bed with a plastic bed cover after sprinkling it down with diatomaceous earth. This stuff kills insects by scratching their exoskeleton and they dehydrate. They have a skeleton on the outside. Very lightly use this dust on the floors because bugs that see dust will usually go around it. Also try not to breath the dust as it is an irritant. Bugs dont develop resistance to Diatomaceous earth like they do to chemicals.

  • PatrickBatman

    I moved in new apt complex which has bedbugs & roaches. I’ve been here 3 months & never seen any in my apt but i’ve also kept it clean, not leaving food out, etc. I havent had to use heat/ac yet but am worried that when i do itll circulate from other apartments and introduce bedbugs etc in my apt. So i can’t use spray in vent, your tape method over vent wouldn’t work for bedbugs right, too small? 90proof alcohol?

  • RanmaCMH

    We live in southern California and we have a recurring fly problem in the summer months; our pest company was pretty unhelpful about trouble shooting the issue. They seem hung up on the fact that they can’t spray them or treat them but they don’t have any knowledge about what do about them besides that.

    From what I’ve found online they look like blowflies (housefly size, irridescent green on their backs) but act like cluster flies (tons of em, hanging out by warm windows, suddenly appearing when it gets hot, just don’t have the body coloring they’re supposed to have??) We’ve got a really clean home, and since the infestation we’ve been excessively deep cleaning to make sure they don’t have a food source but we can’t figure out where they are coming from or things we could do to keep this from happening again. We can keep trapping and killing them but ideally we’d like to STOP this from happening over and over. Help! Ideas??

  • BeantownBeatdown

    If you have any success please return and give info, my wife is going out of her mind with gnat/fly problems in the summer months in our home last year we thought we tackled them all with the drain method.

    I’m traveling now for business and she says sure as the day is long, they are back at it, all over the place. They are such a nuisance and they don’t play by any of the normal gnat/fly rules they avoid almost every trap and the pesticide that was sprayed seemed to just agitate them into attacking our faces/eyes.

    It’s enough to make a person batty. So any help you find for the problem we’d be glad to hear it! Thank you in advance and hopefully you find a solution either way.

  • Jeff

    I’m getting repeatedly bitten daily on my lower legs by some bug ever since moving into my new home in NJ. I rent the upstairs dormer. I’m trying to rule in/out various bugs. The bugs cold be flea, tick, chigger, mosquito, but I’m leaning toward BEDBUG, because: This morning, I had the “usual” bite pattern ON MY FOOT – where my shoe would prevent bites; EXCEPT IN BED (as I don’t wear shoes to bed, of course…). My bed is an air mattress that I brought from a non-bed bug home. Also, it was in my van when the van caught fire traveling from Detroit to NJ, so I washed it in vinegar and baking soda, and see zero evidence of bed bug on it – or anywhere else in the room or on my stuff. In my room, there is a small, defunct heating vent on the wall, in the corner at the floor, at the foot of my bed. There is a new HVAC on demand system that does not use this useless vent. The bed bugs could be hiding in there. I’ve bombed the room twice and that hiding place would not get the bomb benefits. Should I seal up the vent? If so, with what? Home Depot blown in insulation from a small tube/can, etc.? I bought the bed bug spray – should I spray that first? Use the clear packing tape? All of the above? I rent, and there are other people living here without bug bites – only me. Thanks, Jeff

  • TG

    I’d recommend (as a pest control operator) you check with a physician first. First step is the identify the pest before you do any spraying. If you aren’t seeing any pests, nobody else is getting bit, and its only on your foot – it could be something else. Many skin conditions can look like bites. If it isn’t a pest problem, then you’ll just be wasting your time & money no matter what treatment you do… and at the end of the day the problem won’t get fixed.

  • TG

    Check for a dead animal somewhere. Blowflies breed in dead carcasses & garbage. If you keep a clean home, then there is something dead nearby. Check the attic/under the house (or make your bug guy do it). If you can get rid of that you can get rid of the problem.

  • sara

    I just moved into an apartment in Southern California and seem to have a spider problem. They all look the same- thick, brown, about half an inch in diameter. I don’t know where they are coming from. Used to find them on the ceilings and high up on the walls where the wall and ceiling met, but ever since laying down sticky traps, have been finding at least one or two new spiders each morning. Help! I even had the apartment maintenance come by and put caulking in any opening they could find. Seriously going crazy.

  • sara

    Also I should add that we have had pest control come by and spray something but that doesn’t seem to work at all.

  • BeantownBeatdown

    Firstly, thank you for the reply!

    I placed some clear tape over our guest bathroom vent (very old system doorstairs haven’t been able to renovate it yet)

    Haven’t seen any since then, had a pro look through the system (aside from being pretty darn dusty in unreachable areas to our swiffers) nothing dead unfortunately. But he put some sort of strips toward the inside and asked me to call him out again next week (free thankfully) to check them and replace them if there are any other issues.

    Haven’t seen any but I’ll definitely call and have him come back out, we’ve been bug free though.

  • Superboy 60

    We have adjustable grill registers in the ceiling. The attic is above it. Small flies start flying around every time the A/C turns on. Opinion?

  • Do you just wish the manufacturers had designed the vents to be sealed properly in the first place…

  • Jeff

    I jut found your answer! It turned out to be FLEAS from
    the CATS!