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Asbestos paper HVAC duct wrap identification & handling: as a visual aid to recognizing asbestos materials in buildings, this article describes and illustrates asbestos paper duct wrap that was usually applied to the exterior of metal heating ducts in buildings prior to 1970.
We describe the difference between asbestos paper wrap or duct seal, asbestos pipe insulation, and hardcast asbestos lagging or plaster used on boilers and pipe joints. We discuss the PACM designation for asbestos materials and we offer general advice for options in handling asbestos paper duct seal and wrap.
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Asbestos paper insulation used to Seal or Insulate Heating Ducts or Air Conditioning Ductwork Exterior Surfaces, Bends, Connections
This document assists building buyers, owners or inspectors who need to identify asbestos materials (or probable-asbestos) in buildings by simple visual inspection. We provide photographs and descriptive text of asbestos insulation and other asbestos-containing products to permit identification of definite, probable, or possible asbestos materials in buildings.
While an expert lab test using polarized light microscopy may be needed to identify the specific type of asbestos fiber, or to identify the presence of asbestos in air or dust samples, many asbestos-containing building products not only are obvious and easy to recognize, but since there were not other look-alike products that were not asbestos, a visual identification of this material can be virtually a certainty in many cases.
This asbestos paper-like material is on the exterior of a hot air supply duct. On homes even into the 1960's we find this material used to seal joints in metal heating ducts.
On older homes from perhaps 1920 the material was often wrapped around the entire duct exterior rather than simply at the joints. Since the duct is normally under positive pressure, any openings in the duct would be more likely to leak hot air out than to suck asbestos fibers into the air path.
If on the other hand we found asbestos material in the air path or on a return duct it would be a more urgent repair topic.
Examples of Asbestos Suspect Material Commonly Found on Heating and Air Conditioning Systems in buildings
We often see what may be asbestos containing insulating material on the heating system, including the following:
The photograph shows asbestos paper duct wrap that has been damaged and is in poor condition. Is this material a hazard? Is it releasing asbestos fragments or fibers into the heating system air ducts?
OPINION-DF: We have not located conclusive data or studies which evaluate hazards regarding specifically the presence of asbestos paper wrap on ductwork in residential buildings.
Like other asbestos fibers in buildings from other sources, if disturbed and distributed in the living area of a building at levels above government standards, there is a potential health risk.
We t 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.
General advice about asbestos suspect paper wrap material on heating or cooling duct work: 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 time to become informed, obtain estimates, and select an appropriate course of action.
If asbestos materials are inside the duct work, such as used for lining of a stud or floor joist bay which serves as an air duct, or perhaps where used as the vibration damper material connecting an air handler to the supply plenum of a system, because of the possible release of fibers continuously and directly into the path of moving air in the building, this material should be removed.
If asbestos materials have been disturbed inside a building without proper containment and cleanup, additional evaluation of the level of asbestos particles in building may need to be evaluated as additional expert cleaning might be needed.
Advice for Handling Asbestos or Asbestos-Suspect Insulation on Boilers, Ductwork, Furnaces
Reader Question: Unknown wrap on ductwork, I think it's asbestos hardcast wrap
I discovered this ductwork covered with this unknown wrap.
I know that the only way to know for certain is to have it tested, but there was nothing in the home inspection about it - assuming the inspector wasn't lazy and didn't lift the tiles - and there was nothing in the home seller disclosure about asbestos, so my gut tells me it's probably just hardcast wrap.
I would like to defer to more experienced eyes, however for a more informed opinion... Many thanks, M.B.
Reply: Definition of Hardcast Asbestos Insulation vs. Asbestos Paper Ductwrap, Definition of PACM, Modern Substitutes
That said, your photo looks very much like a metal HVAC duct that has been wrapped using an asbestos paper wrap.
A few more photos of such material, information about the age of your home and its heating system design and history could increase our confidence in that conclusion, or of course you could test a small piece of the material.
At left we include another photograph of asbestos paper used on an old metal heating duct where the duct makes a 90-degreen turn to direct warm air up through the floor and into a room that is on the other side of the gypsum board partition wall shown in our photo.
I don't use the term "hardcast" asbestos for the material in your photo - I use the term asbestos paper ductwrap or seam wrap because the material is a thin (perhaps 1/8" or less) asbestos paper product, typically applied wet or dampened to allow installation around bends and to adhere to the metal duct surface.
I use the term "hardcast" asbestos to refer to an asbestos paste or "plaster" that was typically applied in a layer of about 1" or greater, used to completely or partially coat old hot water or steam boilers and used on heat distribution piping at elbows or valves. See ASBESTOS on HEATING BOILERS for details.
On heating and other piping installations a similarly thick corrugated asbestos paper wrap was used on the straight sections and sometimes on the boiler exterior and on occasion even in the interior of some warm air furnaces. See ASBESTOS PIPE INSULATION for more images of asbestos on piping.
Hardcast asbestos, when it needs to be removed, is usually handled following a number of asbestos remediation safety procedures (area signage, isolation, dust control, protective gear, etc) and with a "glove and bag method along with wetting, cleaning the exposed metal surfaces and sealing the cleaned surface as well.
Option 1: leave asbestos paper ductwrap in place, possibly covered or spray-sealed:
Best practice is to leave the material you show alone unless other building conditions or very poor condition require its professional removal. Some asbestos contractors use an encapsulant spray or paint where the paper wrap is to be left in place.
As long as the asbestos paper is on the outside of supply ducts (ducts that are normally under neutral or positive air pressure) the chances that asbestos from the paper is entering the duct system and building air are very low. In my OPIION, should we find asbestos materials of any sort inside the duct system or air handler, that is a different (and more serious) concern.
Option 2: remove asbestos paper ductwarap, consider complete duct R&R:
If asbestos-paper wrapped duct seal/insulation does need to be removed for other reasons (building renovations, reconstruction, or materials in damaged, exposed, friable conditions), the removal is handled using asbestos remediation precautions.
But more often it is much less expensive and an easier asbestos abatement job to remove the duct entirely, intact, from the building than it would be to try to remove just the paper wrap followed by duct cleaning. In sum, in most cases it will be easier and less costly to remove old asbestos-wrapped ducts and replace them with new ducts in the same area (if the ducts are still needed) than to try to clean and re-use the old ductwork.
Treat the Material as PACM - presumed asbestos containing material
This material is reasonably treated as "Presumed Asbestos Containing Material" or "PACM". Asbestos "hardcast" asbestos paper and paper tape were used as an air leak seal and slight insulating covering on metal heating ducts usually dating from before 1965 but may have been used up to around 1981.
Contemporary fireproof substitute products for asbestos cloth or paper used on HVAC ducts
A contemporary substitute for asbestos cloth and perhaps as a substitute for fireproof asbestos paper duct-wrap - that is if an application requires fireproof duct sealing material - and for asbestos paper tape (duct joint seal) used in high temperature operations is Silicone Hi-T, a waterproof and chemically waterproof and airtight and non-combustible (and ozone-resistant) flex-duct-connector tape available from
Reader Question on HVAC Duct Asbestos Paper Wrap: should I replace my air ducts?
I think I have asbestos wrapped on some of my heating ducts, on the outside of the ducts. Should I replace these ducts?
Reply: Asbestos paper wrap on supply air ducts & return air ducts
Asbestos paper on the exterior of HVAC supply ducts is unlikely to release asbestos into the circulating air inside the ductwork (since the ducts are under positive pressure), unless the ductwork has been damaged or disturbed.
That is to say that there is most likely an asbestos hazard if the material is in poor condition (torn, shredded, in an area subject to abuse) or if it is likely to be disturbed or has been disturbed.
Asbestos paper on the outside of return air ducts, since they are under negative pressure, if it is damaged, could potentially release asbestos into the duct interior if there are holes or openings nearby in the duct system.
In general, asbestos that is friable (soft, such as pipe lagging and paper) that is in a location to be damaged is just about always a potential hazard, more-so if the material is located in a space occupied by people or in the case of air ducts, if the material might be picked-up and re-distributed through the building by the HVAC system (or by other activities).
Friable vs. Non-Friable Asbestos vs Asbestos Paper Duct Wrap
Friable asbestos-containing-material is any material containing more than one percent of asbestos by weight or area that can (the material) be crumbled, pulverized, made into a powdery substance by the human hand - that is by light pressure and disturbance. If you don't think that paper air duct wrap can be friable check out my two photos just below.
Non-friable asbestos-containing material is also any material containing more than one percent of asbestos but that is hard enough that it cannot be pulverized by hand.
OPINION: Asbestos paper duct wrap is not easily pulverized, but it can be easily torn by hand - an observation that in my opinion means it can be damaged enough to release at least some asbestos particles into the air. However it seems likely that there is a difference in hazard between the amount of material that can be released by tearing paper and the particle release from crumbing pipe lagging or asbestos pipe insulation.
What this means is that panic about asbestos paper duct wrap is not appropriate, but in the problem circumstances I describe the ductwork may merit either encapsulation or removal and replacement by a qualified professional. Any activity such as tearing, duct repairs, drilling, cutting, even disturbing during a duct cleaning operation may release asbestos fibers.
Leave Asbestos Paper Duct Wrap Alone?
Often the asbestos hazard in buildings is much greater from disturbing material than by leaving it alone or sealing it in place. Here is what the US CPSC says about asbestos in their "Asbestos in the Home" publication
However there is nothing in that document that directly addresses HVAC air ducts and blowers where asbestos might be present in the air path. If there is asbestos in the air pathway of an HVAC system such as inside of HVAC ducts, inside the air handler or blower compartment, or damaged asbestos where particles may be picked up into the return air system and redistributed, I would expect experts to recommend elimination of that hazard.
Bottom line: leave asbestos alone if you can. If it's damaged, friable, being disturbed you probably need to do something about it.
Removal vs. Encapsulation vs Replacement of Paper-Covered HVAC Ducts
With all of that general advice and with the reclama that I'm not an asbestos remediation expert, my layperson opinion is that the least hazardous way to deal with suspect ductwork is to either encapsulate the paper ductwork or replace it entirely.
For paper duct covering in good condition that does not need to be disturbed for other reasons, encapsulation (coating, painting, covering with a protective layer) is more economical and less risky than disturbing the ductwork by replacing it.
For ducts that need to be removed, say because of damage or because of other building renovation or repair work, removal is probably appropriate.
Watch out: even if we decide to completely remove asbestos-insulated air ducts, the ducts must be removed by an asbestos cleanup professional using proper methods to assure that the material is disturbed as little as possible and that dust and particle release is avoided and that any additional needed cleaning is performed.
The following is an example of building or home inspection report language when the inspector detects evidence of improper, incomplete, or amateur "asbestos remediation" efforts in a building.
Amateur removal of asbestos from a building can create very serious health and cost concerns because of the possibility that the amateur cross-contaminated other building areas with asbestos debris and also because of the possibility that the asbestos products that were removed were disposed of improperly. we have on occasion found "removed" asbestos insulation simply disposed of by dumping it on the same property or stuffing it into a crawl space or attic.
Improper/Incomplete Asbestos Duct Insulation or Pipe Wrap Removal: Caution: When we observe that a considerable amount of this insulating material has been removed leaving scraps or remainders and without cleaning and sealing of the exposed ducts or piping, we issue the following warning:
Asbestos duct or piping insulation removal has not followed approved methods and procedures: we saw that HVAC duct work or piping has not been cleaned nor sealed, and that the suspect material has been left in some places - details not found when materials were removed by trained professionals.
Unprofessional removal of controversial materials in a building may raise health, legal, or marketing concerns for future property owners. You should attempt to obtain documentation regarding who did what to the property regarding this topic. Additional testing to assure that no hazards or legal issues remain, may involve significant expense. expense; possible, hazardous materials.
Asbestos Paper Duct Wrap
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