Ductwork Connectors & Flexible Duct Connectors

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In buildings of all kinds, the ducts that circulate air for heating and cooling are usually connected to HVAC machinery by flexible duct connectors made out of durable fabric. For many decades, textiles woven from asbestos fibers were the primary material for this application.

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Metal air ducts are commonly used to connect all the rooms in a building to heating, ventilation and air conditioning (HVAC) equipment. However, when ducts are attached to heaters, air handlers and air conditioners directly, the noise and vibrations produced by this equipment may rattle throughout the entire ventilation system.

Years Produced


Construction workers can prevent this problem by installing a flexible duct connector between the machinery and the ductwork. These connectors must be able to absorb constant vibrations and resist hot and cold air circulated by HVAC systems, ideally lasting as long as the HVAC system itself.

For several decades during the mid-20th century, manufacturers thought asbestos to be the ideal material for flexible duct connectors. Naturally occurring asbestos fibers are durable and practically fireproof, yet flexible enough to be woven into fabric, and they could be sourced cheaply from North American mines.

Once the dangers of asbestos exposure became understood by the American public, manufacturers began to use other materials for flexible duct connectors. Unfortunately, many old buildings still contain degrading asbestos materials, and the tradesmen who worked with these materials in the past bear the risk of developing mesothelioma or other asbestos-related diseases in the present.

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Manufacturers began testing asbestos duct connectors as early as 1938, when the Johns Manville Corporation published about their advantages in the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) Journal. In 1951, as air conditioning systems were starting to become popular and affordable for homes, the National Fire Protection Agency officially recommended asbestos for flexible duct connectors.

At a Glance
  • Places Used: Heating, ventilation and air conditioning systems for buildings
  • Toxicity: High
  • Asbestos Use Banned: No
  • Friable: Yes

Some duct connectors were manufactured as simple strips of coarse fabric woven from nearly pure asbestos yarn, which were secured to metal duct joints by clips or rivets. More sophisticated duct connectors were coated with rubber or vinyl to provide a more airtight seal.

As almost all American industries phased out the use of asbestos during the 1970s and 1980s, manufacturers began to switch to cotton canvas or fiberglass mesh for flexible duct connectors.

Manufacturers of asbestos duct connectors included:

Dangers of Asbestos Duct Connectors

During the height of American asbestos use, flexible duct connectors commonly contained large amounts of chrysotile asbestos.

The factory workers who produced these connectors suffered the worst asbestos exposure, followed by the construction tradesmen who installed, repaired or removed asbestos duct connectors on a regular basis. Occupational asbestos exposure is the primary cause of diseases such as asbestosis and pleural mesothelioma.

Furthermore, aging and constant exposure to temperature extremes can cause duct-connector material to become friable, or easily crumbled into inhalable dust. Over time, even rubberized or vinyl-coated asbestos duct connectors can deteriorate to the point of releasing asbestos fibers into the air.

Microscopic asbestos dust has no scent, and exposure generally does not cause symptoms to develop until years later. Because duct connectors are perfectly positioned to affect all the air in a building, degrading asbestos duct connectors pose a serious asbestos exposure risk.


Many people who develop asbestos-related diseases after years of working with toxic duct connectors are able to receive compensation by holding manufacturers liable in court.

For example, in 2005 a retired sheet metal worker named Genaro Garcia won a lawsuit against Duro Dyne. Garcia had been exposed to asbestos in Duro Dyne’s flexible duct connectors throughout his 48-year career, never having been advised to wear respiratory protection, and he developed peritoneal mesothelioma in 2002.

A San Francisco jury awarded him nearly $2 million to cover his pain and suffering, lost earning capacity and medical expenses — including the costs of two years of chemotherapy treatments.

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Daniel King joined Asbestos.com in 2017. He comes from a military family and attended high school on an Air Force base in Japan, so he feels a close connection to veterans, military families and the many hardships they face. As an investigative writer with interests in mesothelioma research and environmental issues, he seeks to educate others about the dangers of asbestos exposure to protect them from the deadly carcinogen. Daniel holds several certificates in health writing from the Centers for Disease Control and Prevention, and he is a member of the National Association of Science Writers.

Walter Pacheco, Managing Editor at Asbestos.com
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3 Cited Article Sources

The sources on all content featured in The Mesothelioma Center at Asbestos.com include medical and scientific studies, peer-reviewed studies and other research documents from reputable organizations.

  1. Asbestorama. (2012). Another Vintage Asbestos Textile HVAC Duct Vibration Dampener.
    Retrieved from: https://www.flickr.com/photos/asbestos_pix/7547697898/
  2. Missouri Court of Appeals. (2006, August 22). Hedgecorth versus Union Pacific Railroad Company.
    Retrieved from: http://caselaw.findlaw.com/mo-court-of-appeals/1303071.html
  3. PR Web. (2005, November 18). SF Jury Finds Chrysotile Asbestos Causes Rare Peritoneal Mesothelioma. Retrieved from: http://www.prweb.com/releases/2005/11/prweb312315.htm

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Last Modified May 21, 2020

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