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In one of my investment properties I’m currently working on, the previous owners apparently used to fry a lot of food, and the greasy smell has accumulated in the ductwork (most notably in the kitchen). I just had a new heat pump installed yesterday, but I still notice that greasy aroma occasionally when it kicks on. This is not flex duct, but rather a fiberboard trunk with round metal branches.
Is there any way to fog the ductwork with some type of chemical? I know there are duct cleaning services out there, but they seem to mostly be for removing dust, and that’s not the issue here. My last option is to remove the branch lines and replace with new flex, which I could probably do myself, but I hate the idea of replacing rigid duct with flex.
You might think the odor is in the kitchen- because that's where it originated; but it will be throughout the duct system- remember, the air is being recirculated.
And no, the only true remediation is replacement. Also; the flex may not be your first choice, but it's probably better insulated than the current hard pipe.
That fiberboard trunk may have acted like a sponge in soaking up the grease. You could try ozonating the crap out of it to attack the volatiles, but be prepared for it to only lessen the smell, while turning any plastics brittle and discolored. Places like Servicepro will have ozone generators for use in fire remediation.
Our previous owners loved those Glade scented candles. In part to mask the fact they had dogs and one was a smoker (99% outdoors/garage). The smell of those candles were on everything from the window screens and blinds, to the paint, and in the hvac system. I got it out of the window treatments by washing the screens and replacing the blinds, and we've painted everything at this point. But could still smell a hint of "winter breeze" every now and then. Figured it out, was in the hvac system. We couldn't replace the duct work, but realized like K' pointed out, the smell was circulated through the system via the intakes. I was able to get 99.99% of it out by doing the following.
1) Replaced all filters with high-quality filters every 45 days for a few months. (still do this actually).
2) Got into each exchange where the evap coils live (have 2 systems) and washed them down with a specialized evap coil cleaner via a pump sprayer. You can utube for instructions on how to do this, actually pretty easy for me.
3) installed atop each evap coil a Honeywell UV light that is meant to kill off germs/odors in the air that passes by it, and also prevents mold/mildew from growing on the evap coils. You can look on amazon for these little marvels of magic - Honeywell UV lights. Very easy to install. My main unit has one above the evap coil. The attic unit that runs the upstairs (bedrooms), has one at the area of the blower motor at the bottom of the system where the air returns feed into it, which is not as effective but better than nothing at all. I can't get one atop of the evap coil on that unit because the box above the evap coil isn't metal (mounting issues).
After washing down the evap coils with the proper solution and installing the UV lights, we immediately noticed a difference in the air quality and odors in our home, especially on the main floor. That was over a year ago when I did this, and it's held up perfectly ever since. In fact, the only stinky things in our house now are US! When we're out of the house for say a day or two and come back home, it smells so nice and fresh when we walk inside for the first time, almost like new construction. Can't say enough about the UV light technology. Has been a game changer for us. But would definitely say that for it to really work at peak levels, it needs to be above the evap coil. When we replace the upstairs unit, we're going to make sure the box above the coil is metal and not this fiber-based thing that's on there now, so we can put the light in that location.
The odor doesn’t seem as bad today since the new unit has been running for awhile, it was pretty strong yesterday though when it was first turned on. Replacing the trunk is not in the budget, but I may end up replacing the branch lines with flex since I do know how to do that myself.
I do have an ozone generator, but from my understanding it’s bad to run ozone through an ac unit. Is that correct?
The odor doesn’t seem as bad today since the new unit has been running for awhile, it was pretty strong yesterday though when it was first turned on. Replacing the trunk is not in the budget, but I may end up replacing the branch lines with flex since I do know how to do that myself.
I do have an ozone generator, but from my understanding it’s bad to run ozone through an ac unit. Is that correct?
Correct. Open a spot just past the coil in that mains fiber duct so the output of the unit is not impacting the coils. You then get to do something that every southern DIY'r will turn green with envy over...
You get to use LOADS of duct tape on actual ducts after putting the generator in place, and then after removing it.
Remember that this is a TEMPORARY remediation job. If there is a load of palpable grease in the duct, do NOT even attempt this, but replace the ducts for safety sake. The unit goes in on a cookie pan or other safe metal base, gets powered on, then after a short time you turn the AC fan on continuous and let things bubble for a few hours (depending on how strong your ozone generator is). Check to make sure the airflow hasn't been seriously blocked, check to make sure the breeze doesn't move or blow over the unit. Don't do it overnight, don't leave the generator running for more than five minutes without the AC fan running as well, and be around hovering until you are certain the process is going completely safely. Once the job is done, remove the unit and re-seal.
I'm not normally as anal about safety precautions, but this is a job where if it goes pear shaped you could end up with a major unstoppable fire. If you have any doubts, don't do it.
Kitchens don't have a RETURN duct (for this exact reason).
Does your house have one?
No, but the hvac wasn’t working the last couple of years the previous owners lived there. I think the odors just sort of rose into that last few feet of duct because the register is pretty much right over the stove. When they turned on the new unit for the first time I just happened to be standing in that spot and that stagment air came blowing out at me.
In that case, I'd just start with the simplest plan possible and go from there. I'd take the register off, soak a sponge in a solution of TSP (hottest water you can handle), stick my hand up there and start wiping the insides of the duct work and see what you come back with. Depending on how smooth the duct work is, I'd use a Mr. Clean Magic Erasure Bar/sponge as well. You might find the odor is right there, say a foot or two inside that duct work.
If the HVAC hasn't been working, then the air and corresponding odors weren't being circulated through the system. We don't have a return register in our kitchen, but it's in the den next to the kitchen and can confirm that it indeed pulls air/smoke/smells out of the kitchen area and into the system when running. Grease? No. Odors? Yes.
The main cause behind the bad odor coming through ductwork is the presence of mold in an air conditioner. The mold will grow on both the condenser coils and in the collection pan. To overcome bad odor problem, need to clean duct on regular basis.
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