Asbestos in or on HVAC ducts (air ducts or heating and cooling ductwork) or inside the air handler (blower unit) itself is a possible hazard for which we provide information, photos, & links to additional documents.
This article shows how to recognize asbestos materials in heating and air conditioning ducts, vibration dampers, chimneys, and flues, and air handlers or blower compartments, and it identifies potential asbestos fiber release or carbon monoxide hazards in buildings where certain asbestos and cement-asbestos transite pipe materials are used for ducts or for heating appliance chimneys and vents.
This is part of our article series that describes the inspection of residential air conditioning systems (A/C systems) to inform home buyers, owners, and home inspectors of common cooling system defects.
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This article describes the inspection of heating and air conditioning ducts for visual evidence of asbestos materials in or on HVAC ducts. We also warn about signs of amateur asbestos removal which may merit additional testing and cleanup work.
The photograph at below left shows asbestos paper heating duct wrap. Asbestos in these locations is a possible hazard which may require special attention, particularly if the paper has been damaged as we show here.
If readers return to the first chapter or view the A/C chapter index, the major components of an air conditioning system are described, sketches and photographs are provided, and common defects for each component are listed along with visual or other clues that may suggest a problem or probable failure of A/C components.
Another example of asbestos duct wrap is shown in this photograph. During an inspection of the heating or air conditioning duct system and air handler, look for what may be asbestos containing insulating material on the heating system.
Caution: Down flow furnace in building with concrete slab and with perimeter duct work raises questions: what is the duct work made of ? Is asbestos material found right in the air pathway in a building? If so there are higher risks of airborne asbestos contamination in that building than otherwise.
Transite chimney Carbon Monoxide Hazards: where used for chimneys in buildings, transite pipe may form a very serious, potentially fatal carbon monoxide hazard due to chimney blockage. We explain how and why the carbon monoxide poisoning hazard develops in our article at Transite Pipes, Chimneys & Flues.
Transite Duct Asbestos Hazards: if used for air ducts transite pipe may be a an asbestos hazard, particularly where the ducts become softened by water exposure (such as air ducts located in floor slabs), potentially releasing asbestos fibers into the building air.
See TRANSITE PIPE AIR DUCTS for details.
Sonno Duct (spun composition material) may have absorbed water, collapsed, and be blocking the duct line and potentially inviting a termite infestation or a mold contamination problem in the building.
Asbestos on Ducts, Health Concern: While there may be no conclusive data nor studies which evaluate hazards regarding presence of this material in residential buildings, it is generally considered by the scientific community to be a potential health risk.
Asbestos on Ducts, Economic Impact: Asbestos heating system insulation is also a potential economic risk as future buyers may be concerned about this material. Disposal costs for this material are increasing.
Depending on condition and location of asbestos material, treatment ranges from doing nothing to complete removal. Removal could involve significant costs.
You should obtain proper technical information and health and safety guidelines before attempting to do anything with this material. It is the breathing of fibers when this material is disturbed, not it's mere presence, which is considered a health risk.
When the material is not found in living areas in poor condition treatment is not usually an emergency and you have ample time to become informed, obtain estimates, and select a course of action.
Offline text files of additional advice for insertion into home inspection reports where asbestos material is observed:
... HEAT.036 - Asbestos - Lab Test Requested (file of inspection report text recommendation)
... HEAT.031 - Asbestos - material unconfirmed; choice of treatment affects. costs
[OPINION - as this advice would change when informed by specific site conditions]
IF the asbestos material is not falling off and creating a mess,
IF the asbestos duct wrap material is not in a location where it's likely to be banged, moved, damaged (thus creating a hazard) and it is not in the air path of the HVAC equipment
You can leave it in place, coating it with a spray-on paint, coating, or wrapping it if it's in a location where it can be wrapped with any suitable duct seal, even aluminum tape.
[this means there is probably a reason to remove the asbestos material]
The least disruptive and least expensive way to remove the material is to work carefully to remove the ductwork itself that is covered in asbestos, in intact sections, with absolute minimum number of cuts or disturbances, for bagging and disposal.
That process is perhaps done by a professional using negative air control to avoid cross contamination, proper bagging and legal disposal, followed by damp wiping and HEPA vacuuming to remove any questionable dust.
First: confirm that the material is indeed asbestos and that its condition or location requires its removal.
If the asbestos-suspect material seen in a building is confirmed as actual asbestos or an asbestos-containing product, depending on its condition and location, treatment ranges from doing nothing to complete removal.
Professional asbestos removal would involve significant costs and is the recommended course of action where asbestos materials are damaged, friable, in a location subject to damage, in an occupied space, and/or in an unoccupied location where asbestos debris is likely to be carried into occupied space by human traffic or by the operation of heating and cooling equipment.
A number of asbestos treatment options are available where asbestos material is found in a building. Choice of treatment can make a big difference in possible costs of handling the material. You should obtain proper technical information and health and safety guidelines before attempting to do anything with this material.
Among asbestos products used in heating or air conditioning air handlers and blowers, we suspect that VIBRATION DAMPENERS, especially in undamaged condition, are likely to release much lower levels of asbestos particles into the HVAC system air than the softer insulating materials found in some air handlers themselves.
We have observed friable asbestos inside older warm air heating furnaces made by Williamson (corrugated asbestos paper insulation inside the air handler of an older unit) and by Armstrong (asbestos insulation around the flue vent connector passage through the air handler's blower compartment side wall - photo shown at left), and in some other brands of heating equipment.
But in our OPINION even in the air handler, depending on the size or amount, condition (undamaged), and location, the release into building air of asbestos from these sources may be very difficult to detect - suggesting that in those cases it is at very low levels, below measurable effect.
Watch out: if there are corrosion leaks or any other openings in the flue vent connector where it passes through the furnace return air side, depending on the blower location several very dangerous conditions can occur, including carbon monoxide production at the burner due to back pressure, or the reverse: negative air pressure (such as will occur in the furnace shown) when the blower is running can extract combustion gases right out of the flue and draw them into building air being passed through the furnace heat exchanger.
Continue reading at ASBESTOS PAPER DUCT INSULATION or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
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I believe I have asbestos wrap covering my water pipes and heating duct work in my 1950's home. The wrap is in good shape, with the exception of a few tears here and there. The article says to leave it alone if possible.
Can I cover these tears myself to avoid airborne contamination with say a piece of duct tape and to avoid having to do total removal, which will probably present a greater health risk? I have a home gym down there and I am very concerned about the health risk especially since I run a fan sometimes. thanks - Diane 6/12/12
Diane there are several procedures that professionals use to cover intact asbestos or presumed-asbestos pipe insulation; in addition to professionally sprayed encapsulants, we've seen good-condition pipe insulation that was simply spray-painted to form a harder skin and to bind any few loose surface particles; other encapsulators wrap the existing insulation with a new plastic or fiberglass covering.
Certainly I would not run a fan in a location that might distribute asbestos-suspect particles. And if there is evidence that the material has been disturbed or damaged in the past, even in small areas, damp wiping and HEPA vacuuming of the area surfaces might be appropriate both to remove suspect dust and to avoid distributing it when you later do run a fan of any sort.
We have an older Sears wall furnace from about 1960 with the corrugated asbestos paper inside the air handler as you mentioned. Two years ago, the paper fell off its mount and lodged about an inch below the top of the exhaust grating, in the top few rows of holes. We continued to use the furnace for the rest of that season, but haven't used it since. I'm curious if you feel this was a serious contamination risk (we've heard people say both possibilities) and if you have any suggestions about removal of the furnace or simply the asbestos paper. Unfortunately, the furnace is in the middle of an open floor plan and will be very difficult to isolate from the rest of the house - Tim 9/28/12
Tim I really can't assess the asbestos risk by just an email; one would need to inspect the system, perhaps performing some tests of nearby dust in the ductwork. While one would be inclined from just your message information to advise against getting too excited, if the paper was in poor enough condition to fall apart, no one is going to bet their mortgage, kids education and car on assuring you that there was no risk of contamination.
The real flies in the ointment are the risk of having blown asbestos dust through a building's occupied space IF there was friable damaged asbestos anywhere in the air path - in that case test building settled dust, an approach that looks more thoroughly than just a momentary air test - and second, even if you removed the asbestos material from the furnace, when you seek to replace it with something suitable, again, nobody is going to be willing to accept responsibility for the safety of the results.
Unfortunately what this has led to for the furnaces I've found that had asbestos built into the plenum and air path has been:
I have a house that was built in 1960. We bought it about a year ago and it has a musky smell. Well this lead us to see what it looked like inside the ducts and heat pump. In the intake ducts it has this board type insulation that's black and yellow. Also inside the heat pump it has insulation where the coil and blower is. Would there be a chance this insulation could be asbestos? It looks like it has been deteriorating for years which means we have been breathing this stuff. Im concern for my 2 year old. - Angela 10/7/2012
Black and yellow fiberglass board insulation is not fiberglass, though if it's in poor condition you may have been blowing irritating fiberglass particles into the building air. A check of settled dust and of air might give an idea of how much dust there is and whether or not a clean-up is justified. See FIBERGLASS HAZARDS for details.
We have just finished having our asbestos professionally removed from our house. However, my husband looked in the furnace and ducts and they were not cleaned at the time of the abatement. We have entered the house a couple of times, are we at risk?? - Erin 11/18/12
Maybe. If the ducts were clean before the asbestos job and if they were properly isolated, sealed and protected during the work you may be ok.
Below someone said he had the "pale paper-like tape" tested and it turned out to be cellulose. I wonder: How do I get the material tested?
In my work as a weatherization auditor/inspector I often find a pale paper-like tape over the seams of some heating ducts in older homes that I have been told to consider as suspected asbestos. A test was done on one of these and that sample turned out to simply be 90% cellulose and 10% fillers and binders, with no trace of asbestos. Was there an asbestos tape used in this way, or is there a way to differentiate between such tapes? - Ken Ray 11/7/11 & again from Jem 11/26/2012
Jem & Ken Ray:
It's easy & inexpensive to send a small sample to any certified asbestos testing lab; The lab may suggest you wet or dampen the sample before snipping it so as to avoid creating any dust. See Where to Find an Asbestos Testing Laboratory - separate article. We also discuss asbestos test labs at ASBESTOS FLOOR TILE LAB PROCEDURES. Typical lab cost is about $50.
For very small amounts of asbestos-suspect material it may make more sense to just treat the material as Presumed Asbestos Containing Material (PACM) rather than face the time delay and lab costs for tiny sample testing.
There are paper like tape seams that do not contain asbestos - usually we see rectangular-grid spaced reinforcing fibers in the newer tapes;
Take a look at how the tape has been adhered to the surface it is covering. Asbestos paper or paper tape strips used on duct seams and on some pipe joints was wet and then applied in strips to seal both metal HVAC ductwork exteriors and to cover some asbestos pipe joints.
You won't (at least in my field experience) see fiberglass reinforcing seams in asbestos paper tape, and the asbestos-based paper tape may be uniformly dimpled over its surface from rolling in the mill.
The edge of asbestos based paper tape is thicker (about 1/16") than modern white seam tapes and was not self-adhesive.
Finally, I wouldn't expect to find asbestos based seam tape on top of or covering non-asbestos pipe or duct insulation itself.
But the opposite is NOT true. That is, in order to cover damaged or friable asbestos pipe or duct insulation, someone might have applied a newer covering material.
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