A chemical or brush that can really clean the surface of an air duct?
December 6, 2021 8:21 AM Subscribe
I got a house to live in, in this overpriced market, but the furnace had been operated for a long time without a filter, and they had pets for many years. I was able to hire a company to clean the bulk of the hair etc. out, but the pros are all stumped on how to deal with the last bit of stuff. I have to figure out how to DIY.
I'm willing to spend a lot of money on it, because it really needs to be solved, but air duct cleaning pros just aren't ready for this, apparently.
I don't even know if it is just the smell, or mold spores or something. It hurts my nasal passages and irritates my eyes. I have to solve it somehow. It's definitely coming from the forced air heating system, and I bought cheap endoscope and inspected the system, and there appears to be no deposits of stuff anywhere that could be the main source of the smell.
It's just the sum of all the large surface area but very thin layer of crud caked onto the ductwork, apparently.
I have tried making an improvised spraying apparatus with a pesticide sprayer from amazon, and some tent pole-like nylon rods that can be connected together. I am able to, with some struggle, finally, spray whatever chemicals in there.
I attached a rag to the end of the rod and rotated it with a drill to try to remove stuff from the round sections of ductwork. I was able to push the rag, rotating, back about 15 feet, all the way through those sections. This is much less practical on the rectangular sections, of course, because the rag doesn't get in the corners.
I can only think of 2 options, but I am open to any way forward that anyone can think of. The professionals are stumped, I had one company cancel their appointment with me when I explained the situation. Another is scheduled for January, but I am highly skeptical they will be able to do anything, because they use the same equipment. I'm stuck trying to DIY, really.
A) Some kind of chemical that will destroy the smelly stuff, which I could spray in there. I have already tried "ez-clean" enzyme cleaner, and followed it some days later with 7 liters of 3% hydrogen peroxide to kill anything in there. They were both allowed to sit for 1 hour after spraying.
But when I put my finger in the duct an swipe some of the stuff off, it still smells. Also the air coming from the ducts still smells a lot, and hurts my eyes and nasal passages. It did help a lot, but it's not enough.
I bought but decided not to use some Thymol, because it leaves a strong and long lasting residual smell. The companies say it dissipates fast, but I think they are only putting a tiny amount in, not enough to make a difference anyway. I can tell because the stuff is $50 a gallon and they only charge $40 extra to do the "treatment". It took me 6 liters of ez-clean to really coat the ductwork with a fluid layer, it would take a similar volume of Thymol solution.
I did an experiment with bleach, and it also leaves a smell that I fear would persist for months. And being a strong oxidizer, I thought hydrogen peroxide would work just as well, plus it is totally volatile, leaving no issues behind it.
Maybe stronger peroxide, like 12 percent, but I haven't been able to find a source for 6 liters of 12% peroxide anywhere.
B) Some kind of highly conformal wire brush, which has sharp ends, but conforms well enough, would help a lot. The brushes I have been able to find are way too stiff. To really scratch the stuff right off, but also contact all the surfaces that are in there.
Then I have to actually get it out of the duct somehow, possibly with the help of a duct cleaning company's giant vacuum, possibly with the rag system. Again, the geometry of the rectangular ducts poses a problem here. It's not easy to get the rotating rod thing into the rectangular ducts, either, but I can cut holes etc. if I have to.
I was thinking a round brush made of steel wire, but with each bristle that comes radially away from the central hub, you also attach some shorter bristles to it which are perpendicular to that original bristle. Thus, it is more prone to getting the tips of some of the bristles against the wall of the duct. It's the tips that really scratch, after all. I could try to make such a brush, but that seems like an uncertain, difficult undertaking that might not work anyway.
The ducts are all galvanized steel, fortunately, no fiberglass or whatever.
Ideas?
I'm willing to spend a lot of money on it, because it really needs to be solved, but air duct cleaning pros just aren't ready for this, apparently.
I don't even know if it is just the smell, or mold spores or something. It hurts my nasal passages and irritates my eyes. I have to solve it somehow. It's definitely coming from the forced air heating system, and I bought cheap endoscope and inspected the system, and there appears to be no deposits of stuff anywhere that could be the main source of the smell.
It's just the sum of all the large surface area but very thin layer of crud caked onto the ductwork, apparently.
I have tried making an improvised spraying apparatus with a pesticide sprayer from amazon, and some tent pole-like nylon rods that can be connected together. I am able to, with some struggle, finally, spray whatever chemicals in there.
I attached a rag to the end of the rod and rotated it with a drill to try to remove stuff from the round sections of ductwork. I was able to push the rag, rotating, back about 15 feet, all the way through those sections. This is much less practical on the rectangular sections, of course, because the rag doesn't get in the corners.
I can only think of 2 options, but I am open to any way forward that anyone can think of. The professionals are stumped, I had one company cancel their appointment with me when I explained the situation. Another is scheduled for January, but I am highly skeptical they will be able to do anything, because they use the same equipment. I'm stuck trying to DIY, really.
A) Some kind of chemical that will destroy the smelly stuff, which I could spray in there. I have already tried "ez-clean" enzyme cleaner, and followed it some days later with 7 liters of 3% hydrogen peroxide to kill anything in there. They were both allowed to sit for 1 hour after spraying.
But when I put my finger in the duct an swipe some of the stuff off, it still smells. Also the air coming from the ducts still smells a lot, and hurts my eyes and nasal passages. It did help a lot, but it's not enough.
I bought but decided not to use some Thymol, because it leaves a strong and long lasting residual smell. The companies say it dissipates fast, but I think they are only putting a tiny amount in, not enough to make a difference anyway. I can tell because the stuff is $50 a gallon and they only charge $40 extra to do the "treatment". It took me 6 liters of ez-clean to really coat the ductwork with a fluid layer, it would take a similar volume of Thymol solution.
I did an experiment with bleach, and it also leaves a smell that I fear would persist for months. And being a strong oxidizer, I thought hydrogen peroxide would work just as well, plus it is totally volatile, leaving no issues behind it.
Maybe stronger peroxide, like 12 percent, but I haven't been able to find a source for 6 liters of 12% peroxide anywhere.
B) Some kind of highly conformal wire brush, which has sharp ends, but conforms well enough, would help a lot. The brushes I have been able to find are way too stiff. To really scratch the stuff right off, but also contact all the surfaces that are in there.
Then I have to actually get it out of the duct somehow, possibly with the help of a duct cleaning company's giant vacuum, possibly with the rag system. Again, the geometry of the rectangular ducts poses a problem here. It's not easy to get the rotating rod thing into the rectangular ducts, either, but I can cut holes etc. if I have to.
I was thinking a round brush made of steel wire, but with each bristle that comes radially away from the central hub, you also attach some shorter bristles to it which are perpendicular to that original bristle. Thus, it is more prone to getting the tips of some of the bristles against the wall of the duct. It's the tips that really scratch, after all. I could try to make such a brush, but that seems like an uncertain, difficult undertaking that might not work anyway.
The ducts are all galvanized steel, fortunately, no fiberglass or whatever.
Ideas?
I don't even know where to start with cleaning this and am really feeling the notion of replacing everything or effectively encapsulating it but, for the meanwhile, did you know that they make register filters?
posted by teremala at 9:43 AM on December 6, 2021 [1 favorite]
posted by teremala at 9:43 AM on December 6, 2021 [1 favorite]
Are you sure the air coming out of the furnace is OK before it goes into the ducts?
posted by clew at 10:15 AM on December 6, 2021 [2 favorites]
posted by clew at 10:15 AM on December 6, 2021 [2 favorites]
Replace the ducts -- you might get better insulation, with newer materials/standards.
We have a Moby Dick-grade drama with our central air system, and replacing the soft duct work in the attic was a morning's work for them. (It didn't help, but that's a story for another day.) Replacing the hard ducts is a bigger ask, but because they are rigid, they could be easier to scrub.
Maybe DIY removal of the old soft ducts, scrub the hard ducts, and have a contractor install new soft ducts?
posted by wenestvedt at 10:20 AM on December 6, 2021
We have a Moby Dick-grade drama with our central air system, and replacing the soft duct work in the attic was a morning's work for them. (It didn't help, but that's a story for another day.) Replacing the hard ducts is a bigger ask, but because they are rigid, they could be easier to scrub.
Maybe DIY removal of the old soft ducts, scrub the hard ducts, and have a contractor install new soft ducts?
posted by wenestvedt at 10:20 AM on December 6, 2021
We got new ducts. You might get a quote for how much that would cost, plus an estimate of the energy savings you'd get from it; over some number of years it'll be cheaper to replace than to keep running the older less efficient system. Our need is A/C more than heat, but for us the energy savings of getting a new efficient system were quite significant. We also got some sort of up-front energy rebate (can't recall if from energy company or from the city) for updating to a more efficient system. Plus, we didn't have to try to get ducts cleaned from the prior homeowner's pets.
posted by nat at 10:27 AM on December 6, 2021
posted by nat at 10:27 AM on December 6, 2021
Response by poster: hm, encapsulation, replacing the ducts or these high velocity ducts... hm. all pretty expensive options. It just seems like the quantity of matter that is contaminating things is probably quite small, if I could only get it somehow.
I don't know what you mean by soft ducts, it's all galvanized sheet metal. Some areas have small amounts of wood in them, which could be encapsulated, however that's a small enough fraction of the system I can probably just leave it as is.
posted by Nish ton at 10:39 AM on December 6, 2021
I don't know what you mean by soft ducts, it's all galvanized sheet metal. Some areas have small amounts of wood in them, which could be encapsulated, however that's a small enough fraction of the system I can probably just leave it as is.
posted by Nish ton at 10:39 AM on December 6, 2021
Response by poster: Maybe a hepa register filter would help in the meantime.
posted by Nish ton at 10:40 AM on December 6, 2021
posted by Nish ton at 10:40 AM on December 6, 2021
Yeah, better filters will help. But a filter that is stronger (i.e. effective on a smaller particle size) will slightly decrease the efficiency of your system. (Worth it if you can breathe better obviously).
posted by nat at 10:44 AM on December 6, 2021
posted by nat at 10:44 AM on December 6, 2021
An ozone generator may oxidize the odorants to an acceptable level. They're commonly used for mitigating smoke smell. Caveat: make sure you pay attention to safety and local regulations before using. Breathing ozone isn't good for you.
posted by grokus at 10:57 AM on December 6, 2021 [6 favorites]
posted by grokus at 10:57 AM on December 6, 2021 [6 favorites]
Beauty supply house like Sally's sell hydrogen peroxide from 10 to 40%. It also comes in a cream form that would stick to the duct work better.
posted by stray thoughts at 11:57 AM on December 6, 2021
posted by stray thoughts at 11:57 AM on December 6, 2021
So, duct cleaning in general is a liiiitle scammy. The reason it's a liiiiitle scammy is that, while yes, dust accumulates in ducts, ducts are usually a very inhospitable place for any form of bacteria to live. It's too hot or too dry to really encourage bacterial or mold growth. Most air moves really quickly through ducts, so it is rather unlikely to "pick up" enough irritants to really reach you. Often, duct cleaning "uncovers" gross layers that were insulated inside the duct by dust, or it will loosen up things to be picked up by the air. Those layers haven't been sanitized by the hot air/dryness yet, and so it can be gross for a bit.
You've... taken that to the next level. You've introduced a lot of moisture into the ducts, which could, unfortunately, lead to more mold growing and stuff in there.
Vent filters are okay but adding air resistance on the back end of a duct means the air will still escape, in the walls and spaces that the duct is running. This will probably be fine, but it will make the air flow slightly less good.
My recommendation:
1. Turn up the heat, and leave the windows open for a full day. Let everything "settle".
2. Make sure the intake into the furnace is clean, healthy air.
posted by bbqturtle at 12:19 PM on December 6, 2021 [2 favorites]
You've... taken that to the next level. You've introduced a lot of moisture into the ducts, which could, unfortunately, lead to more mold growing and stuff in there.
Vent filters are okay but adding air resistance on the back end of a duct means the air will still escape, in the walls and spaces that the duct is running. This will probably be fine, but it will make the air flow slightly less good.
My recommendation:
1. Turn up the heat, and leave the windows open for a full day. Let everything "settle".
2. Make sure the intake into the furnace is clean, healthy air.
posted by bbqturtle at 12:19 PM on December 6, 2021 [2 favorites]
Following on bbqturtle, we quit having our ducts vaccuumed because every single time the stress knocked some joint loose and we started getting dust sucked in from within the century-old walls of the house. (Horror face appropriate.) Also not energy efficient!
After the last hasslesome taping up of the accessible ducts, we switched to getting v good filters for the furnace intake and switching them on a rapid schedule. And I still daydream about switching the house back to radiant heat somehow.
posted by clew at 12:49 PM on December 6, 2021 [1 favorite]
After the last hasslesome taping up of the accessible ducts, we switched to getting v good filters for the furnace intake and switching them on a rapid schedule. And I still daydream about switching the house back to radiant heat somehow.
posted by clew at 12:49 PM on December 6, 2021 [1 favorite]
Commercial Grade Ozone Generator. Set your furnace to run the fan continuously, set the generator up full blast at the entrance to the return air duct and let it run. It would be best if you could leave it running for a couple days but you don't really want to be in the space so doing this when you're away for the weekend would be ideal. Otherwise fire it up when you go to work and turn it off when you get home for a few days. Either way ventilate well when you get back. Or you can just wait; Ozone degrades to regular O2 in an hour or so.
posted by Mitheral at 2:39 PM on December 6, 2021
posted by Mitheral at 2:39 PM on December 6, 2021
Can you get to the spot with the really dirty duct in your attic or whatever? Rigid ducts are just held together with screws. Maybe you could take it apart, clean that one section really good, and then put it back together with the screws and duct seam tape.
posted by The_Vegetables at 2:54 PM on December 6, 2021
posted by The_Vegetables at 2:54 PM on December 6, 2021
You can also remove and replace one section with flexible ducting (again with the seam tape to hold them together) if you are moderately handy.
posted by The_Vegetables at 2:55 PM on December 6, 2021
posted by The_Vegetables at 2:55 PM on December 6, 2021
Response by poster: Thanks guys, it's hard to show my appreciation. It's hard to pick one as best answer, partly because it's hard to know what would work. I will look into the different possibilities suggested. I did investigate dismantling the ducts, but it would be extremely difficult. Developing a method of cleaning them in place seemed more promising.
Ozone is something I will investigate more, but if peroxide didn't do it, I don't know if ozone will. It is after all very similar, a strong oxidizer.
I have bought some furnace filters with a 1900 particle capture efficiency rating, so suitable for allergens, and started taping them over the output vents. So 8 separate filters, at $26 each.
To my surprise, it appears that it may be helping a lot, however it is not clear yet. This would support the hypothesis that it is small particles of pet dander or other matter escaping from the walls of the ducts, which somehow survived the two chemical treatments with enough integrity to still cause an allergic or other reaction, causing the smell and irritation of eyes and nasal passages.
I may yet replace the ducts, but it would be so expensive I think I might switch to some kind of water heating plus convection based baseboard radiators thing. It would be an opportune time to install solar heating, if I could get some solar thermal panels that would make sense. I am surprised solar space heating is not more of a thing, but it appears to be a niche. Usually the panels are for domestic hot water, and thus more expensive and give higher temperatures than needed for space heating.
An encapsulant for the ducts is also a promising option, but getting it in there without getting it everywhere is a challenge, and identifying a good product that would work for the challenge. I could just use odor-blocking water based paint stuff, and dilute it with a bit of water so it flows through the nozzle, perhaps, but that might not work for one reason or another... better to get a product specifically suitable for the task.
posted by Nish ton at 10:30 AM on December 7, 2021
Ozone is something I will investigate more, but if peroxide didn't do it, I don't know if ozone will. It is after all very similar, a strong oxidizer.
I have bought some furnace filters with a 1900 particle capture efficiency rating, so suitable for allergens, and started taping them over the output vents. So 8 separate filters, at $26 each.
To my surprise, it appears that it may be helping a lot, however it is not clear yet. This would support the hypothesis that it is small particles of pet dander or other matter escaping from the walls of the ducts, which somehow survived the two chemical treatments with enough integrity to still cause an allergic or other reaction, causing the smell and irritation of eyes and nasal passages.
I may yet replace the ducts, but it would be so expensive I think I might switch to some kind of water heating plus convection based baseboard radiators thing. It would be an opportune time to install solar heating, if I could get some solar thermal panels that would make sense. I am surprised solar space heating is not more of a thing, but it appears to be a niche. Usually the panels are for domestic hot water, and thus more expensive and give higher temperatures than needed for space heating.
An encapsulant for the ducts is also a promising option, but getting it in there without getting it everywhere is a challenge, and identifying a good product that would work for the challenge. I could just use odor-blocking water based paint stuff, and dilute it with a bit of water so it flows through the nozzle, perhaps, but that might not work for one reason or another... better to get a product specifically suitable for the task.
posted by Nish ton at 10:30 AM on December 7, 2021
Being a gas ozone will get places you can't get liquids like inside the heat exchanger of the furnace.
posted by Mitheral at 12:38 PM on December 7, 2021 [1 favorite]
posted by Mitheral at 12:38 PM on December 7, 2021 [1 favorite]
Response by poster: update: the filters on the ducts don't really work much. They appeared to work at first, but it seems likely that it was just some chemical coming off the filters that was masking the smell.
I searched for information on ozone odor removal, and a bunch of odor removal companies popped up that I had not been able to find in all these months of actually explicitly searching for odor removal companies, cleaning companies, etc.
I called some and got through to someone at one, who says you need like 200 grams per hour for six hours to effectively do odor removal. Probably further research is needed to ascertain if this is true and how much you really need.
The generators on amazon are like 10 grams per hour, so that's not going to work, if what he says is true. I caught him bullshitting a bit so it needs further research.
In any case, I am strongly considering ozone now, but searching for a more cost effective way to do it. They guy I called quoted $750 plus tax for one treatment, no guarantees it would even work.
posted by Nish ton at 12:43 PM on December 7, 2021
I searched for information on ozone odor removal, and a bunch of odor removal companies popped up that I had not been able to find in all these months of actually explicitly searching for odor removal companies, cleaning companies, etc.
I called some and got through to someone at one, who says you need like 200 grams per hour for six hours to effectively do odor removal. Probably further research is needed to ascertain if this is true and how much you really need.
The generators on amazon are like 10 grams per hour, so that's not going to work, if what he says is true. I caught him bullshitting a bit so it needs further research.
In any case, I am strongly considering ozone now, but searching for a more cost effective way to do it. They guy I called quoted $750 plus tax for one treatment, no guarantees it would even work.
posted by Nish ton at 12:43 PM on December 7, 2021
The local Cresco equipment rental place rents the Zontec PA2500 for $134 a week. So, pretty cheap to try. It's a 2.5 gram unit, but check because air is only 21% oxygen and some units list a pure O2 capacity which is not your situation. I think 200 grams is a clear miscalculation. If I take a 1000 square foot house with 10 ft ceilings, at medium odor, thats 1000*10*0.018 = 180 milligrams per hour. 200 grams would be a half-million square foot house. Do be careful with ozone, it's very bad for humans and can destroy certain materials. But it is great at taking care of odor. It would never occur to me to attempt to physically wash my ducts with liquid.
posted by wnissen at 4:59 PM on December 7, 2021
posted by wnissen at 4:59 PM on December 7, 2021
Response by poster: I am strongly considering/trying to do ozone. I think I should still try to clean the rectangular ducts with the rotating rag first, though, as it may easily remove 80 percent of the matter in there or something. It won't solve the problem but can be a part of the solution.
Yeah, I think that guy was lying to me about the total ozone generation capacity.
The rentals are far more expensive over here. There is no one that does it in my city, and I called Toronto, which is 5 hours away, and a unit is $180 per day there. He is supposed to text me about the capacity of the unit.
For $750, I can just buy 3 10g/h units on amazon. However I fear they might not actually produce what they say they will. You can buy ozone meters, too, however they are extremely expensive, more than $1000 each for a decent one.
I don't think 180 gm per hour would do much, based on all I have read you do need more than that. Each ozone molecule can only destroy one molecule of volatile, smell - causing chemical, so the amount of ozone needed to destroy the substances in the house is going to be significant.
Good quality information is scarce, but I found one blog post type thing that attempts to share some relevant and reasonably good quality information, including quantities etc. here https://www.mychemicalfreehouse.net/2019/07/using-ozone-to-clean-up-toxins.html
I may buy the units and then put them *in* the ventilation system, and block the vents off. I would still need to leave the house, but it would concentrate the ozone to the inside of the ducts. Some leakage will always occur so there is still some O2 to convert to O3. At 10 grams an hour, air weighs about a kg per cubic meter, and that's 200 grams of O2. Plus, when the ozone degrades it goes back to o2. So I am skeptical of this supposed need for ventilation when using the machine. More likely any ventilation will just dilute the O3.
I called several companies in various cities to try to get some traction on what needs to be done, how to do it, caveats, etc. and information is scarce. It's clear there is a lot of scamming and swindling going on in the industry. Same as duct cleaning. Great.
I am inclined to buy the units, then I can try as many times and in various ways, take my time on the prep etc. If I hire the guy, he comes once, it turns out he has rinky dink machines or they are not working right, or he doesn't seal the house right or something else doesn't work out, and then that's it, game over. If I buy the generators, I learn about the technology for future reference, can try repeatedly in various ways and be sure the run time etc. is legit. My main concern is that the machines are not going to actually produce anywhere near what they claim to. There is nothing that ensures they do, no regulatory body, no nothing.
posted by Nish ton at 10:10 AM on December 9, 2021
Yeah, I think that guy was lying to me about the total ozone generation capacity.
The rentals are far more expensive over here. There is no one that does it in my city, and I called Toronto, which is 5 hours away, and a unit is $180 per day there. He is supposed to text me about the capacity of the unit.
For $750, I can just buy 3 10g/h units on amazon. However I fear they might not actually produce what they say they will. You can buy ozone meters, too, however they are extremely expensive, more than $1000 each for a decent one.
I don't think 180 gm per hour would do much, based on all I have read you do need more than that. Each ozone molecule can only destroy one molecule of volatile, smell - causing chemical, so the amount of ozone needed to destroy the substances in the house is going to be significant.
Good quality information is scarce, but I found one blog post type thing that attempts to share some relevant and reasonably good quality information, including quantities etc. here https://www.mychemicalfreehouse.net/2019/07/using-ozone-to-clean-up-toxins.html
I may buy the units and then put them *in* the ventilation system, and block the vents off. I would still need to leave the house, but it would concentrate the ozone to the inside of the ducts. Some leakage will always occur so there is still some O2 to convert to O3. At 10 grams an hour, air weighs about a kg per cubic meter, and that's 200 grams of O2. Plus, when the ozone degrades it goes back to o2. So I am skeptical of this supposed need for ventilation when using the machine. More likely any ventilation will just dilute the O3.
I called several companies in various cities to try to get some traction on what needs to be done, how to do it, caveats, etc. and information is scarce. It's clear there is a lot of scamming and swindling going on in the industry. Same as duct cleaning. Great.
I am inclined to buy the units, then I can try as many times and in various ways, take my time on the prep etc. If I hire the guy, he comes once, it turns out he has rinky dink machines or they are not working right, or he doesn't seal the house right or something else doesn't work out, and then that's it, game over. If I buy the generators, I learn about the technology for future reference, can try repeatedly in various ways and be sure the run time etc. is legit. My main concern is that the machines are not going to actually produce anywhere near what they claim to. There is nothing that ensures they do, no regulatory body, no nothing.
posted by Nish ton at 10:10 AM on December 9, 2021
10 grams is 10,000 milligrams. Hundreds of milligrams is plenty for a U.S. sized house. But ducts are just metal and sealing materials. They don't have the capacity to hold much odor. It's probably in the walls and floors, which are porous.
posted by wnissen at 12:54 PM on December 9, 2021
posted by wnissen at 12:54 PM on December 9, 2021
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However, it sounds like it would be easier to just entirely replace the ductwork.
Or, if not, then change out the HVAC system to use a high-velocity distribution system instead (basically, this means putting new smaller ducts inside your existing large ducts). Spacepak is one such manufacturer.
posted by aramaic at 8:32 AM on December 6, 2021 [1 favorite]