Asbestos in Ductwork Connectors and Flexible Fasteners

For several decades during the last century, asbestos was used to manufacture duct connectors that could resist heat. Asbestos fibers were ideal due to their durability and fireproofing quality, and their flexibility allowed them to be woven into fabric. It wasn't until the 1980s that manufacturers began using other heat-resistant materials to produce duct connectors. As a consequence, many old buildings still contain degrading asbestos components in their ductwork.

Ducts that ensure warm or cool air inside the buildings are usually connected to machines with flexible duct connectors made of tough fabric. For many years, woven asbestos materials were used to make these connectors in the U.S. In a typical older home or building, metal air ducts connect all the rooms to HVAC equipment, enhancing the noise and vibrations produced by the equipment. The noise and shaking could travel through the entire ventilation system without a connector between the machinery and the ductwork.

By installing a flexible duct connector in between, noise canceling was fixed. Still, the connecting piece had to absorb vibrations and resist hot and cold air from HVAC systems. Asbestos fit the bill and abounded the markets, so the industry jumped on the accessible material and used it whenever possible. Asbestos tape became the go-to sealant for air ducts in:

• heating
• ventilation
• air conditioning

However, besides asbestos tape, there were other types of asbestos ductwork connectors used in sealing the system, such as:

• Coarse fabric connectors - simple strips of material woven from nearly pure asbestos yarn, secured to metal duct joints by clips or rivets.
• Vinyl or rubber-coated duct connectors - asbestos pieces were coated with rubber or vinyl for a more airtight seal.
• Paper duct connectors - asbestos paper containing about 15% chrysotile asbestos was used as duct wrap insulation in older homes and buildings, especially in basements and attics.

Asbestos May Be a Health Risk in Older Homes or Buildings

Over time, asbestos products crumple due to wear and tear, breaking down into asbestos dust composed of microscopic asbestos fibers. The tiny threads are invisible to the naked eye and can linger in the air for hours, exposing everyone to inhaling or ingesting them. Workers who installed and repaired asbestos ductwork connectors often developed asbestos-related diseases decades later. However, because no amount of asbestos exposure is safe, older house owners and their families may face the same risks whenever asbestos products are disturbed in their homes, including components of the air conditioning system:

• asbestos cement
• millboard
• insulation

Asbestos cement pipes were typically used as air ducts rather than connectors. Asbestos millboard usually was the heat shield on walls and ceilings around HVAC systems. Asbestos wrap insulation lined the inside ducts to improve heating or cooling efficiency.

With all these asbestos components in the ductwork, every homeowner or building manager should prioritize safety when renovating or repairing. Although there are safe DIY methods for handling asbestos, it's always wiser to call a licensed professional and let them remove the hazardous products.