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Transite and Other Non-Friable Materials High in Asbestos Content

Transite Panel Removal

Did you know that some non-friable materials can have high asbestos content? Often when thinking of high asbestos concentration in materials we assume these to be friable materials. While friable materials such as thermal system insulations are typically higher than most non-friable materials, there are some materials that are on par. Transite, asbestos gaskets, and galbestos are examples of this. They are typically asbestos mixtures of concrete or metal components and are typically used for sidings and other building components. 


Transite is a mixture of asbestos and concrete manufactured by John Mansville starting in the 1920s and phased out in there 1980s. Transite can be found in the siding on houses, sheds, garages, and roofing. Transite can also be found as piping, HVAC ducts, lab hoods and tables, and gutter systems as it was coveted due to its durability. 

Transite incorporated asbestos for its heat resistant properties and because it allowed the concrete to become more durable and less permeable. Due to the properties of asbestos, it mixes easily with concrete. When transite becomes aged and worn, the material can become friable in some cases. This can be very problematic if it occurs in an HVAC duct. 

In my lab experience, I have seen transite range from 20-50% asbestos concentration, typically of the chrysotile variety. Transite is still being produced to this day, but with silica rather than asbestos. As is similar in all concrete, improper disturbance of the newer variety may cause exposure to silica.

Asbestos Gaskets

Gaskets form a critical part of mechanical systems. They are used to seal areas of pneumatic systems and other various mechanical processes. Due to the heat resistance and durability of asbestos, it was used in gaskets. Asbestos gaskets would have been ideal for systems using steam, gases, or caustic compounds.  

Ring gaskets are a common variety of asbestos-containing gaskets, which are commonly composed of metal and asbestos. Other forms of gaskets that are composed of asbestos-containing rope or sheet gaskets are considered to be friable. These types are used in areas of high temperatures, such as furnaces. In my lab experience, gaskets can range from 20% to the 70% range, but it is possible for gaskets to be lower or higher than these ranges.  


Galbestos is a steel, felt asbestos mixture that is used as a siding (like transite). Galbestos stands for galvanized asbestos. The process of creating galbestos is galvanizing zinc or iron with asbestos and asphalt. Galbestos can be found on the exterior of older warehouses and other structures. Similarly to transite, galbestos — once aged — can be rendered friable. Surprisingly, galbestos samples were rare in the lab. Anecdotally from fellow local analysts, galbestos has a similar asbestos content to transite. 


These materials demonstrate that not all higher concentration asbestos-containing materials are friable. However, damage and age can render transite, gaskets, and galbestos friable, thus making them more hazardous. If you suspect you have these materials at your property, contact Indoor Science to assess them for asbestos.

Ian Cull

Ian Cull is a nationally recognized expert in the field of indoor air quality. He is the Chief Science Officer of Indoor Science, a company he started in 2004. He speaks around the world on air quality topics and is a training provider of the Indoor Air Quality Association. Mr. Cull is a Licensed Professional Engineer (PE) and Certified Industrial Hygienist (CIH). His degree is in Environmental Engineering from the University of Illinois - Urbana Champaign. Mr. Cull has developed 50 air quality related courses for the IAQA University and is the author of the book, “Fundamentals of Mold Remediation”. In his words… “Besides being passionate about indoor air quality, I enjoy cycling, music, the Chicago Bulls, and having fun with my three kids.”

3 thoughts on “Transite and Other Non-Friable Materials High in Asbestos Content

    My daughter’s home is a 1961 Ranch home on a slab in a Chicago suburb . She has ducts in the slab and they were recently tested to determine if the ducts were Transite. The test came back positive as being Transite, 15% asbestos. She was told by the asbestos tester that she needs to have an asbestos abatement contractor seal off the ducts. When she called an abatement contractor, the contractor said that transite is not friable so you can seal off the ducts yourself and you don’t need an asbestos abatement contractor to do the work. Who is correct, the asbestos tester or the asbestos contractor? She did have her ducts professionally cleaned shortly after moving in and after jack hammering was done on the slab to repair a damaged sewer line. The ducts have been filled with water an a frequent basis as well. My daughter plans to put in a down flow furnace so she will need abandon the ducts in the slab anyway.

    Hello Elaine,

    I would agree more with the asbestos inspector. Transite is non-friable, but I don’t recommend dealing with an asbestos-containing material without a licensed asbestos professional performing the work. Depending on the age and wear of the material, non-friable materials can be rendered friable.