Rodents damage air duct. What to do??? Help!

PatintleDecember 4, 2005

We found bunch of insulation and plastic came out of the heat register last week. Yesterday we found a HOLE in the air duct! I am pretty sure it's from rodents since there was dark brown droppings the size of 3/4" in the garage and our instant noodles were eaten. the rodents bait were taken as well. I would really appreciate advice on

i) how to make sure the rodents are out of the heating system,

ii) how to track where else the ducts might be damaged (could be inside the duct), and

iii) how should I fix/cleanup/ or replace the air duct!

We has a year contract with Terminix. But that does not seem to help preventing rodents! The pest control guy came in the put down 4-5 glue traps, but didn't capture any. Now I'm trying to find out on my own how to clean up and fix the ducts so we can get the heating system back on ASAP! It's pretty cold in the house since we turn off the heating system, being very concern about the health risk that might come witht the warm air that blows up from the damaged ducts with possible rodents feces. There are dark droppings INSIDE the duct right where the hole is (and the insulation came off). The insulation came up on the registers both on 1st and 2nd floor of the house. My house was built in 1989, The duct that has a hole is vinyl.

Again, anyone who has experience or knowledge on how to fix - I would really appreciate your help.

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Rodents are a real pain in the neck!
Find out if Terminix will return until they are gone.
Rodents make noise.
listen for movement at night.
Avoid poisons. If you poison them they may die in your house's ductwork. Not good.
Best to trap them. Tie a string onto a mouse trap of proper size for your particular rodents and slide it into the vent.
Be careful with the droppings. Some rodents may carry the Hanta Virus. Let the Terminix guys deal with the droppings.
Find out how they are gaining access to your house and seal it up with steel wire.
You mention insulation, that means they are out of the heating sys. and into the walls. Look for holes in the walls too. Check your wiring for damge too.
If you have access to the ducts from below, buy a short length of vinyl pipe with a slightly larger diameter. Cutout a section big enough to cover the holes and use a two-part epoxy to affix it to the outside of the duct. If you can reach the hole fron the vent end, use the same diameter pipe and glue it on the inside of the duct. If your rodents are quite small and the holes are not very big,(less than an inch) you could try expanding spray foam.

Get rid of the rodents first though. They love to build nests out of expanding foam.

Try to put some pressure on the Terminix guys to expedite their work. Rodents tend to breed like... well, like Rodents!

Good luck finding Mickey,


    Bookmark   December 4, 2005 at 11:58PM
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I had that problem in a add on duct run, heating guys who did it are too lazy to use the metal, Arughhh! I had it replaced with a metal run..
From the size of the droppings, I'd say its a rat! hate them things!
Find where they are getting in first! I see people's garage doors open all the time, and I think "well, I bet they got mice!" haha...

    Bookmark   December 5, 2005 at 1:10AM
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Thanks a lot Katoo and crableg!

I guess i might need the duct replaced too, but I don't know which section. How to find out which part has damaged, especially if it starts from the inside?

Do you know if replacing air ducts is "DIY" project? If you ever had it done, is it a high cost project? Thanks!

    Bookmark   December 5, 2005 at 7:42PM
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Guess it could be DIY, If my hubby was alive, he could have done it, I might have even done it, if I could crawl under the house, haha, them days are over!
All my ducts are metal, except that add on, and now it is also.
Are all your ducts flexable? I hope not, you have to find the source of invasion first, then repair damage...

    Bookmark   December 5, 2005 at 8:20PM
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Some sections of the air duct are vinyl, some are metal, according to my husband who went down the crawlspace. May be I should replace with metal one, but don't know how to get that thing under the crawlspace! We found quite a long gap where the duct went from furnace into under crawlspace and have fix that. My husband also fixed a gash in the duct. But we don't know if there's any other holes where rodents come in. I have tried to put pressure on Terminix and they'll send 2nd person to inspect. Hopefully he has better solution in finding the gaps/holes that need fixing...

    Bookmark   December 5, 2005 at 10:49PM
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I would replace ALL flexable with metal, if I were you, it comes in short enough pieces, (flat) to get it under there, it it asembled as you go to proper lenght, it is cut with tin snips and sealed with furnace tape. Just hire it done, worth everything to get rid of the rodents!

    Bookmark   December 6, 2005 at 10:31PM
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Thanks a lot crableg. I got similar info from a heating company that replacing just a section with metal is not effective because the rodents would be able to damage the ducts that are still vinyl. So the solution is to replace all of them, or just make sure the rodents are out of the system. I decide to replace the section that is damaged with the same flex duct, and have the duct system cleaned and sanitized. I also found from CDC web site that the glue trap is not recommended since the mice might urinate and spread Hanta virus. The snap trap is recommended.

Here are some links that might be useful to others:
-> How to deal with rodents from CDC:
-> The benefit of duct cleaning to prevent health problems is inconclusive:

    Bookmark   December 7, 2005 at 2:13PM
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Help. Every time my furnace comes on I can smell urine. I'm pretty sure it's a mouse ... but where? Is it IN the ductwork, or ON the ductwork? Could it be in the bottom of the furnace itself? I've set snaptraps and caught one. I've also placed rodenticides, and I knonw I probably shouldn't have, because they can go back to their nests and die there. I'm at my wits end. Should I call a furnace guy, a duct cleaner, or an exterminator? I'm getting sick - literally.

    Bookmark   December 26, 2007 at 4:20PM
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I'm sorry to hear about your rodent problem! I dealt with that a while ago in winter and it was not fun. (we had to shut down the furnace.) Does the urine smell stronger in one room more than other? Where did you catch the rodent? Perhaps look into the duct close to where you caught the rodent? If you're able to, have you tried inspecting the air ducts in your home to see if there're any holes or insulation coming out? I noticed mine first from the insulation that came out of the duct. Rodents like to make nests from insulation materials. Try inspecting your crawlspace insulation as well - you might see droppings, urine. I'd try to talk to pest control company and see what they can do to help. In my case, what Terminix did was putting traps and baits but we didn't catch any rodents. It helped me feel a little better that there isn't any more rodents. I use a company that did crawlspace clean-up, insulation and duct works. The salesperson came and inspect the crawlspace and told us what needed to be done. You may want to try to find such company and talk to them as well. Good luck!

    Bookmark   December 27, 2007 at 1:14AM
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I've never done it but have heard of wrapping flex duct with hardware cloth to keep rats/mice out of ductwork.
One contractor told me he used felt paper.

If I had to choose I'd opt for the hardware cloth.
After replacing the damaged flex.

best of luck.

    Bookmark   December 27, 2007 at 3:26PM
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You mention noodles being eaten. In addition to blocking ALL holes with metal (have you thoroughly checked other places besides the ducting?) you should probably make sure that all food (including stuff in the garage like spare grass seed, bird seed, anything a rodent might like to eat) is put in something rodent tight. Metal cans, the fridge etc. If you have pets, make sure you feed them, they eat it, and you don't have pet food laying around. No food, they typically move on, at least as soon as winter is over.

    Bookmark   December 28, 2007 at 1:30PM
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