Photo Guide to Asbestos Paper Wrap on Air Ducts

How to recognize asbestos paper duct wrapping materials in buildings - Photographs of asbestos paper duct wrap in buildings
Heating and Cooling Duct Asbestos Paper Wrap Risks
Examples of Asbestos Suspect Material Commonly Found on Heating and Air Conditioning Systems in buildings
ASBESTOS DUCTS, HVAC - separate article
ASBESTOS TRANSITE DUCTWORK - separate article
DUCT SYSTEM & DUCT DEFECTS - separate article
Questions & Answers about how to identify asbestos paper sealant,coating, or insulation on heating ductwork
References

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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.

Asbestos Paper Duct Insulation Identification & Handling

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.

Also see ASBESTOS DUCTS, HVAC a field identification guide to visual detection of asbestos in and on heating and cooling system ducts and flue vents.

Photograph of asbestos paper wrap on heating/cooling duct exterior

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:

Cement asbestos "millboard" used as a partial heat shield on wall/ceiling surfaces.
White corrugated insulating material on and hanging from pipes, white paste material surrounding certain plumbing joints.
White "paper" wrapped on outside of some heating ducts.
White woven material used as flexible joint between some heating ducts.
White woven material used as flexible joint in the vibration damper between air handler the duct work.

Heating and Cooling Duct Asbestos Paper Wrap Risks

Photograph of asbestos paper duct wrap in poor condition

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.

Frequently Asked Questions (FAQs) About Asbestos Paper Duct Wraps & Seals or Insulation

Question: Unknown wrap on ductwork, I think it's asbestos hardcast wrap

I love the forum, but didn't know how to post this image for advice. My kitchen has a drop ceiling that we had to lift to accommodate a plumber coming in to repair a leaking stack.

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

A competent onsite inspection by an expert usually finds additional clues that help accurately assess how much ductwork or other asbestos-suspect materials may be present in your home.

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. 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 Carlisle Coatings & Waterproofing, INc., 900 Hensley Lane, Wylie TX 75098, Tel: 800-527-7092, Website: www.hardcast.com [copy on file in our records as Hardcast-Hardware-Catalog-Final-25.pdf ] Carlisle C&W, under the brand name Hardcast(R) distributes a wide range of tapes and seam sealers.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

3/07: thanks to Gary Randolph, Ounce of Prevention Home Inspection, LLC Buffalo, NY, for attentive reading and editing suggestions. Mr. Randolph can be reached in Buffalo, NY, at (716) 636-3865 or email: gary@ouncehome.com
06/07: thanks for photographs of transite asbestos heating ducts, courtesy of Thomas Hauswirth, Managing Member of Beacon Fine Home Inspections, LLC and (in 2007) Vice President, Connecticut Association of Home Inspectors Ph. 860-526-3355 Fax 860-526-2942 beaconinspections@sbcglobal.net
June 1997 - Window Putty - OSHA case cites contractor for asbestos exposure during removal of window putty http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=NEWS_RELEASES&p_id=1091
Asbestos Identification and Testing References

Asbestos Identification, Walter C.McCrone, McCrone Research Institute, Chicago, IL.1987 ISBN 0-904962-11-3. Dr. McCrone literally "wrote the book" on asbestos identification procedures which formed the basis for current work by asbestos identification laboratories.
Stanton, .F., et al., National Bureau of Standards Special Publication 506: 143-151
Pott, F., Staub-Reinhalf Luft 38, 486-490 (1978) cited by McCrone

Asbestos in Your Home U.S. EPA, Exposure Evaluation Division, Office of Toxic Substances, Office of Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington,D.C. 20460
Asbestos products and their history and use in various building materials such as asphalt and vinyl flooring includes discussion which draws on Asbestos, Its Industrial Applications, D.V. Rosato, engineering consultant, Newton, MA, Reinhold Publishing, 1959 Library of Congress Catalog Card No.: 59-12535 (out of print, text and images available at InspectAPedia.com).
"Handling Asbestos-Containing roofing material - an update", Carl Good, NRCA Associate Executive Director, Professional Roofing, February 1992, p. 38-43
EPA Guidance for Controlling Asbestos-Containing Materials in buildings, NIAST, National Institute on Abatement Sciences & Technology, [republishing EPA public documents] 1985 ed., Exposure Evaluation Division, Office of Toxic Substances, Office of Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington,D.C. 20460
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