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How to treat your air vents for bugs

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by The Bug Doctor

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 Picture 19 300x246 How to treat your air vents for bugspuzzled 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.


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  • Jerry Bires

    I’ve a brown recluse infestation and I’ve got glue traps wedged into every register/duct opening in the house. I routinely catch them. I wonder how many I’m missing, however, and wanted your opinion on whether having the ducts cleaned professionally would help eradicate the spiders that are not leaving the ductwork at night to hunt.

  • Jerry Bires

    I’ve a brown recluse infestation and I’ve got glue traps wedged into every register/duct opening in the house. I routinely catch them. I wonder how many I’m missing, however, and wanted your opinion on whether having the ducts cleaned professionally would help eradicate the spiders that are not leaving the ductwork at night to hunt.

  • The Bug Doctor

    I’m surprised that brown recluse would be in the vents with the air going on and off. As stated this usually is too much for the bug and the dehydrating factor causes them to find another place to live. You may have a break in a tube and any spiders in the attic might be what you really need to treat. For that I’d hire an exterminator to use a fog machine and treat.
    Cleanings not a bad idea if I’m incorrect because that will destroy the nests and oust out the spiders. I had mine cleaned a couple years ago and it was amazing the amount of dirt and debris. However in all that, not one bug. Check the vent tubes in the attic first and then make your decision.

    Thanks for reading
    The Bug Doctor

  • The Bug Doctor

    I’m surprised that brown recluse would be in the vents with the air going on and off. As stated this usually is too much for the bug and the dehydrating factor causes them to find another place to live. You may have a break in a tube and any spiders in the attic might be what you really need to treat. For that I’d hire an exterminator to use a fog machine and treat.
    Cleanings not a bad idea if I’m incorrect because that will destroy the nests and oust out the spiders. I had mine cleaned a couple years ago and it was amazing the amount of dirt and debris. However in all that, not one bug. Check the vent tubes in the attic first and then make your decision.

    Thanks for reading
    The Bug Doctor

  • Bob Stewart

    What do you do if your cold air returns just empty into the crawl space?  Every few months my granddaughter and/or I are getting a single bite from something, and it has to be coming in through the air return.  Short of having an exterminator come in (and it’s currently winter in Indiana) what can I do besides just tape the two bedroom vents shut?

  • http://pestcemetery.com The Bug Doctor

    You really shouldn’t consider any treatment until you’re sure of exactly what is biting you. There are no pesticides that I know of that allow for treatment of ‘unknown’ bugs. Even with that, I’m not a fan of putting any pesticide in a vent, plenum or other system where the air is used inside for heating or cooling. Once you figure out what it is that’s biting you- then you can devise a plan to get the critter out— Partial tape on the vents (vents where the air comes out or where you suspect activity) is a great way to figure this out– you should be able to see what gets stuck on it and then start your plan from there.

  • Bob Stewart

    Thanks very much for your reply.  My problem with using tape is that I’m only getting bitten every few months, and I doubt my dedication to the task of cleaning and checking tape will last that long.  =)  But I am giving it serious thought.  Is there any type of tape that is best?  I have some Gorilla brand black duct tape that is extremely sticky.  Use that sticky side out around the hole?

    I also contacted the County Extension office at Purdue to see if they had any comments; since they’re here in Indiana.

    One thought I had was to have someone install a 6 foot length of HVAC tubing on the cold air returns down in the crawl space to take advantage of  the dehydration factor you’re talking about, above.  I’m disabled now, so I can’t just go down and do this stuff for myself anymore.  My biggest quandary is just what specialty to call to try to resolve this problem: HVAC?  Pest control?  Someone else?

  • http://pestcemetery.com The Bug Doctor

    I’d say just some packing tape so it’s clear and you can see both sides (sorta) of whatever you catch. Since you’re only getting bit every couple of months, do you think it could be something else? Is there some other common denominator that fits in that time line? It certainly doesn’t ring any bells of normal activity of any critter I know of.

  • Drtinyod

    I have large black roches the size of Pomanto bugs coming up from my air vents, how can I treat this problem? I live in Tennessee and it dosen’t mater if it’s summer or winter. Can I spray my air vents and then close them off for two weeks? This problem started about a year and a half agi.  I don’t have any other kind of roches.

  • http://pestcemetery.com The Bug Doctor

    Are you a crawl space home? If so & your ducts are underneath, you may have a tear in one and by simply repairing that, you’ll solve the problem.

  • Pennycruz

    surprised that I cannot find any info re preventing bugs from entering the home through the air vents which are on the floor in my case.  My thought is to make a screen for the opening (which has a little ledge ) which is part of the metal air duct and let it rest on the ledge.  What do you think? thanks for your input

  • http://pestcemetery.com The Bug Doctor

    Generally speaking critters do not enter this way unless there is a break in the duct work. (which I’ve written about) At that point it is as simple as fixing the tear, break or separation of duct work to solve the problem. If however you can’t get to the problem then I think your screen idea just might be a good one.

  • Bbaker1968

    I would love to add that I had spiders coming from my vent in my bathroom. I bought some screen and nailed it up over the vent and now have no more problems.

  • http://pestcemetery.com The Bug Doctor

    I think that would keep em out! Thanks for reading my blog and adding to the conversation.

  • WannaB Gnat Free

    I am almost sure these tiny jumping flying gnats are coming from my air conditioner vents. I usually kill about a dozen a day in the bathroom. They line in the bathroom tub or walls mainly, occasionally on the floors. I have had pest control come out four times to spray and pump blue liquids in the drains. I have no other clue where they could be coming from. These gnats are so small, I’m not sure if the tape trick will work. Please help. Any advice would be appreciated.

  • http://pestcemetery.com The Bug Doctor

    There are so many posssiblities when it comes to gnats. If your company ID’d them it could make narrowing the source down much easier. Having said that, there are so many different kinds and I don’t even always know which kind either. The drains were a good thought but with 4 treatments I’d say that isn’t it. Your vent idea could be true but you’ll need to crawl in the attic (if that’s where your a/c ducts are) and see if there is a break in them and possibly find the source… i.e.; dead mouse, water leak etc. Gnats in bthrms often originate from leaks behind the walls. You may have a leaky pipe, crack in shower pan or even a crack in pipe below the slab. If you have a known moisture problem, fix that first and I have a hunch you’ll have no more problems. Also- before even the a/c vents- I’d check the bthrm exhaust fan. The vent usually goes through the roof or is just laid in the attic. If not sealed properly or of leaves or other debris accumalates (for the roof vent) then all kinds of critters will hang out and from there, make their way in.

    I LOVE your comment name & I think a gazillion people a day share it. Gnats are SOOOOO frustrating. Just start out with the obvious- looking for moisture, checking screens, exhaust fan, (don’t forget any new plants you may have brought in) and then move to the more complex. a/c vent etc… If in between, you can get a positive ID, you’ll jump several steps ahead on where to search and what to do.

  • Virginia Abell

    I have cellar spiders coming through the vent/fan above my shower.  Of course the other side of the vent is the attic so it makes sense.  I thought about closing up the fan from the attic with that foam sealant but I like the idea below about nailing a screen to the other side.  How small should the squares of the screen be to keep out the cellar spiders? I feel like they could squeeze through anything.

  • http://pestcemetery.com The Bug Doctor

    Cellar spiders do start our small but I’d think a standard window screen (perhaps doubled up) would keep them at bay.

  • sobia

    our apartment complex is new, and we are paying big money for it as well. I suppose in my mind, if i paid more money for an apartment I wouldnt have to worry about bugs or scorpians. So, we moved in and everything was fine until crickets showing up left and right out of no where. At first we thought, it probably happened when we come in and out of the apartment, but we only left and came once in the day, and kept a close eye. We kept telling out complex management, and they said we need to deal with it. Then, i realized after a lot of investigation and sleepless nights that they are coming from our vent, specifically our living room vent. Management sent maintenance over and he just said perhaps there is a crack, he apparently sealed it and left. Nope, that didn’t fix the problem. So, my husband and i went to home depot and purchased mesh, and lined the vents with it. Miraculously the crickets stopped coming in, now we only had to worry about the outside/surrounding of our apartment (but that’s a whole different story.) So, todayyyy around 4 Am, i find my cat standing on our dining table looking upwards at the track lighting. i walk in to realize that there is some heavy noise coming from the track lights area, and it almost sounds like either something hopping, trying to get out, or something slightly bigger moving around. My concern now is are we still at risk for our lives, i know i sound a little dramatic, but (well, i have a bug-phobia.) I havent slept in so many nights because of this issue, and finally when i was getting a wink of sleep, we’re at square one. Also, im equally afraid that they are going to start hopping out from our ceiling fan onto us during the night, since they are so active. Unfortunately, my phobia started because about a decade ago when i used to live under my parents, and in an apartment, crickets began to hop out of the fan. I think i’ve never been able to live that down in my mind, so i just need a solution or peace of mind that they shouldn’t be coming out from anywhere else.

    Thank you so much and i really will be thankful to you forever if you answer this question please.

    -Sobia

  • http://pestcemetery.com The Bug Doctor

    I would check your states laws but–I’m pretty sure the landlord is responsible for providing pest control service by law. For your crickets problem the problem is an exterior one–there are cricket baits and sprays that’ll make short work of them for sure. For those inside. Sealing up is your best bet as you already did but you can’t go around sealing everyone else units. I would dust the voids and kill them in the walls before they start popping out.

  • Amyluebbe

    There is a very annoying cricket stuck in my air vent (we have floor vents so it can’t just jump out). any ideas on how to get rid of it? You can’t hear it in every room!

  • Amyluebbe

    That was supposed to say you CAN hear it in every room

  • Romeo Gonzalez

    Lets see the landlord does spray the apt when asked but I’m getting these small bugs that fly coming from the vents and its driving me nuts is there a defogger strong enough to use that will eliminate these bugs

  • http://pestcemetery.com The Bug Doctor

    I wouldn’t use a fogger because they have ‘no off button’ For such a small space it would be a mess. The source needs to be ID’d first which you can do using a little packing tape over the vent and see what you get. From there you can narrow down the source and take better steps towards a solution. My guess is it could be something IN the duct work that needs to be removed to rid the bug of their source of food or hatching…..but you won’t know until you figure out what bug it is.

  • John

    I think killing insects and spiders is wrong. They feel pain. I don’t think the fact that they are scary or annoying or want to live in my house gives me the right to kill them. Instead, I use easy, harmless catch-and-release methods to get them out of my house. Is there any such method I can use to get them out of my air vents to release them outside?

  • http://pestcemetery.com The Bug Doctor

    Hi John– I appreciate your opinion… I’d assume to get them out of a vent you’d need to construct a trap of some sort that would catch em as they tried to crawl out… Tough to do… I’ll give it some thought…let us know if you come up with something

  • Andrea

    I’m wondering about ants. I think we have ants living in our vents (they come out every couple days out of a different vent). I hadn’t thought about not spraying vents (I’ve been spraying Raid on the ants and the vent every time they come out of one) but won’t do that anymore after reading your article. This has been going on for a couple months and my landlord says because it’s ants it’s my problem. Any suggestions?

  • http://pestcemetery.com The Bug Doctor

    I’d try Advion ant gel-or they sell the same type of bait in a tiny plastic station – (not a gel but same ingredients )- works very well. Also– Most state laws indicate it is the landlords responsibility for pest control, you might want to check into your state laws and see.

  • Maria

    We found pantry moths in the cupboard above the stove where the stove fan vent is. We cleared out all the food and washed the cabinet but whenever we run the stove fan and the upstairs bath fan we get pantry moths flying around the kitchen and bathroom. Is it possible they are living in the fan ductwork and how would we get rid of them

  • http://pestcemetery.com The Bug Doctor

    It may not be pantry moths as that seems an unlikely place–but hey, after 30 years I can’t say it’s impossible…. Check out my video on treating bathroom vents and the techniques may help. http://pestcemetery.com/big-roaches-big-trouble-bathroom/

  • http://www.facebook.com/david.mav.33 David Mav

    We have big roaches coming out of vent. We have seen couple of times ourselves. Usually it happens when we turn on cold air. We are in first floor of an apartment complex. What should we ask of pest control from apartment complex to do, since last time they just did few things in kitchen and bathroom but nothing for vents or ducts. Can we put in thin mesh liners around each vent just to avoid them coming in our house? It’s tough to sleep in peace with 2 year old knowing that roach can pop out anytime, though it has happened only in kitchen and bathroom so far. Thanks.

  • http://pestcemetery.com The Bug Doctor

    The mesh sounds OK but I would not spray IN them whatsoever, bugs are one thing but breathing recycled pest products wouldn’t be good. Are you sure they’re coming from INSIDE the vents? Normally this isn’t the case unless there is a break or tear in the vent…in that case, sealing it is your best option.. You could remove the vent cover and place a sticky trap (secure it with tape so it doesn’t blow around when air kicks on) inside the duct and that would confirm it for you….Generally they are coming from AROUND the edge of the vent and that you just need to have them snug up tighter and it should help.

  • Mike

    My roaches have come through the vents. and they seem to only come if the A/C is on. However, I’ve only seen 4 or so but the pattern seems to be that they fall from the vent in the kitchen and plummet to the tile floor so they are easily caught. I’m on the top floor so my safest assumption would be to have someone clean the ducts. But I’d like something until I can get that appointment placed.

  • http://pestcemetery.com The Bug Doctor

    Maybe tape it off a bit (the vent) placing the strips a 1/2 or so apart over the vent. This should allow the air to come through but still catch your roaches until you have the duct cleaned and or repaired (have them check for holes,rips or separations-my guess is that’s what’s happening)

  • J

    I sure hope you can help We have little back bugs crawling out of 2 vents I sweep up about a 100 or 200 every day, from the kitchen floor. I have remove the covers and they are crawling all over. they are very tiny.What are they and how do i get rid of them?

  • http://pestcemetery.com The Bug Doctor

    Most likely need a pic to venture a guess. You can send one via my Ask The bug Doctor Tab on my site. http://pestcemetery.com/bug-doctor/

  • cathy

    We had a bird build a nest in our microwave vent about a week ago. Now we are seeing tons of little white bugs crawling on the cabinets, microwave, stove, etc. I have sprayed bleach on everthing but they keep coming back by the dozens. We have someone coming out tomorrow but what can I do in the meantime – I am completely grossed out!!

  • Patrice

    My neighbors have a Roach infestation, we’ve only seen a few roaches in our home. The neighbors are moving out, and the owner is having an exterminator come, so they can sale the house. If my home is clean will I still get roaches? Also should I have an exterminator come to our home too?

  • http://pestcemetery.com The Bug Doctor

    It depends on what type of roach to some degree. If it is German roaches & your homes are not connected, then I’d say you have no worries. The larger roaches such as American or Australian or Oriental prefer outdoors already so they may be lurking regardless.

  • http://pestcemetery.com The Bug Doctor

    I’d simply wait for the pro.

  • home owner

    What can you do about centipeds in large numbers. they seem to be coming from the vents. Some are big, in dark brown or maroon color and when I say alot I mean alot! is there anything I can out in the grss or around my home?

  • http://pestcemetery.com The Bug Doctor

    a granule barrier around the home and a good dust applied to the gaps and cracks followed up with caulk.

  • NovacaneCandi

    A cricket has been stuck in my wall ac unit for the past 2 days. What can I do to get it out? All of the chirping is annoying!!!

  • http://pestcemetery.com The Bug Doctor

    Not sure if you can slide a sticky trap inside the unit or puff some Niban bait inside, but either would work. These two links may help with ideas; http://pestcemetery.com/getting-creative-with-pest-control-sticky-traps/
    http://pestcemetery.com/love-niban/

  • scaredofspiders

    what can i do if there seems to be a spider nest in my car vent? i tried to run the heat to drive them out, but as i tried to catch one, the others crawled back inside.

  • http://pestcemetery.com The Bug Doctor

    If you can pop the vent out ( I can with mine) maybe you can put a vacuum hose down there. I doubt they’d be real deep. There are non residual aerosols like CB 80 or CB 40 that you could “puff just a small amount into vent that may work…Not an aerosol like Raid that is a jet type stream..the 80 or 40 come out in a mist or fog….there is no residual but even so I’d run the fan to get any smell out.

  • Dennis

    Roaches and termites, I want to hook up my car exhaust to my house after i seal it up, and put two carnaries in a cage in the front room so i can see them from the out side. Has any body done this before??

  • Rajkumar Pappu

    I seem to have a typical problem with insects and they show up from the vent on the floor in the room and come up only when the weather is warming up a little. When we start the heater they are thrown out of the vent and it happens typically when the weather rises to about 40 F. Most of them are dead when they are thrown out. Need some solution for the same.

  • http://pestcemetery.com The Bug Doctor

    If possible check the duct lines to see if there is a break in one (or more) allowing pests to enter. You could also have the ducts cleaned by a service. That would eliminate the problem most likely.

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