Transite HVAC air duct hazard FAQs.

This article series explains the potential hazards of transite (cement asbestos) air ducts - asbestos fiber release, radon, and indoor air quality concerns, and duct collapse when transite air ducts are is found in buildings.

Transite Pipe HVAC Ducts: Asbestos Heating or Air Conditioning Duct Material Warnings

These questions & answers about the environmetal hazards of transite-asbestos air ducts were posted originally at x - be sure to review that information too.

Question: can I seal a crack in a transite HVAC duct?

Can a crack in a transite HVAC "duct" be sealed or repaired. I am having foundation issues with my slab on grade living room and one of the ducts is cracked. - Brad 8/6/11

Reply:

Brad transite is a cementious product. It could be "repaired" using a bonding agent and high-portland content patching cement, and perhaps even duct seal. 

There are also duct-sealants that some contractors offer as an in-duct sealant/spray. A down-side with in-slab ductwork is the difficulty in accessing for application of the spray and difficulty in inspection in the future to see what's going on inside the duct: collapsing walls, sealant falling off of duct interior, flooding, mold, asbestos-releasing scraps, rodents, etc. 

But given the history of concerns with the product, in particular with in-slab ducts, I'd give strong consideration to abandoning in-slab ductwork entirely.

Question: Water leaked into our transite air ducts - is this a problem?

I had some water get into my transite pipe buried into the slab of my house. I stopped the water by putting a new cement slab and redirecting the water. I immediately dried it up with a wet vac and kept the air conditioning on. I obviously have a leak in the pipe and have noticed some debris which I had removed by a HVAC vacuum company. I was told by an inspector when I bought the house that the transite probably had asbestos. Is this a problem? What should I do ? - Jack 9/22/12

Reply:

Jack: I'm not sure which concern or problem you were asking about.

Basically if you abandon an in-slab transite pipe duct and seal the floor (you added another layer of concrete over your original floor slab) so that it can't easily send radon, rats, or mold into the building, it's not much of a concern - the cement-asbestos material won't move up through the new slab and thus won't be an ongoing asbestos hazard.

Your inspector, by saying that transite "probably had asbestos" was perhaps trying to please the seller and real estate agent from whom s/he receives referrals. Transite HVAC ducts are a cement-asbestos product and contain about 50% asbestos materials (fibers and powder filler) by volume.

Because it's in a cementious form the transite duct material is not normally friable so is less likely to release significant levels of asbestos into building air than softer asbestos materials such as asbestos pipe or boiler insulation. But when water-damaged or mechanically damaged, the asbestos release hazard from transite ducts can increase significantly.

Question:

What should a homeowner do about a transite air duct system? Is it a health hazard? I have two 12 - 15 foot lengths of HVAC ducts under a slab portion of my home. The ducts look to be in good shape through visual inspection from the floor vents with the exception of one crack (see post and answer below). If I want to stop using the ducts, what should I do as far as sealing them off from the furnace? I have installed a gas burning insert in the room so I can get away without using the ducts. Any help would be greatly appreciated. - Brad 6/11/12 

Reply:

If you abandon use of a transite duct, and provided it's not damaged so as to have become friable (releasing dust, easily crumbled between your fingers) it can be left in place - it's not "radioactive" - and is better left undisturbed. Don't run power tools, saws, grinders, etc. on cement asbestos material. But in the article above we give some reasons why in-slab air ducts of any sort present indoor air quality risks and hazards from future and un-discovered flooding, rodents, mold, etc. Add to that the risk of softening (asbestos fiber release) from water or moisture condensation in the ductwork, and the collapse risk. I'd prefer to abandon the in-slab ducts (SLAB DUCTWORK) and seal off those supply registers.

With that approach, and as long as there are not other slab cracks that leak contaminants into the building, it may not be necessary to try fill the entire in-slab duct with cement or other fillers, and the material can safely be left in place.

Question:

(Apr 3, 2014) Anonymous said:
About transite air ducts, and asbestos cement air duct issues: Was there a time frame these asbestos cement ducts were installed, or are they still being installed today?

Reply:

Transite asbestos HVAC ducts are not currently installed in any country that I know about, nor is the material used for new water pipes, chimneys etc. The time frame for cessation varies by country, generally late 1970's to early 80's.

Question:

(July 13, 2014) Anonymous said:
Where transite ductwork is found to contain asbestos, should the furnace also be replaced/

Reply:

No, there is no justification for furnace replacement on that basis. But cleaning may be appropriate.

To be clear about the wording of your query, transite duct is not "found to contain asbestos" - it does contain asbestos.

Question:

Is it justified to replace the furnace because there was asbestos dust contamination in the ductwork?

Reply:

It's likely that there has been some airborne asbestos through the duct system and the air handler, though just how much depends on a number of variables including the amount of damgaged asbestos, moisture levels (water in in-slab ducts may have reduced the hazard though produced a different mold issue), air velocity, other dust levels, and surly other variables.

Unfortunately, when I've run into this sort of issue (which I've seen a few times) the cost estimate from the cleaning company to properly and thoroughly clean the equipment is greater than the replacement cost.

Your options are to inspect, identify the highest risk locations and test dust and debris from those areas for asbestos, acting accordingly on the results, (probably spending a few hundred dollars on testing), or to just replace the equipment.

If the furnace is more than 20 years old I'd lean towards replacement of furnace, ducts, and other parts that are not easily cleaned.

On 2018-05-02 21:07:59.554698 by (mod) -

cement mixed with asbestos shorts as filler and with long asbestos fibers

On 2018-05-02 19:41:26.191453 by Ripon

What does used to material of asbestos pipe & flue pipe. Rphossain@gmail.com send me details

On 2018-03-12 17:13:44.882891 by (mod) -

Office

I would like to see and perhaps comment on the photos - you can attach images to comments by using the picture frame icon to the right of the Comment button.

On 2018-03-12 13:16:05.489351 by Office Building & Failed, Buried Transite Duct

I have photos of a below-grade, under-building, HVAC duct labeled in the 1965 drawings as Transite duct (24" diameter and up); It appears to have a spiral, interior finish. At the point of failure, it appears as if that lining has pealed down across the duct. Two such ducts beneath the building are so blocked (collapsed). Effectively being in an in-earth-embedment, confined space, I am enlisting advice on how to such may be best renovated. If best to abandon, then how best to put in a replacement under the building.

The building is an exposed structure design (no suspended ceilings). Horizontal air distribution occurs through these below-grade ducts which feed into vertical chases that then feed double-slab plenums and perimeter floor diffusers at each floor.

On 2018-02-06 16:48:08.667015 by (mod) -

Jaylin

Please use the picture frame icon to the right of the comment button to send us photos one by one of the containers and their labels. That will allow further and perhaps useful comment.

On 2018-02-04 11:01:12.498230 by Jayln Morrison

I'm not sure if or how it was used but I have found a can of the johns manville cement in one of my garages and in this garage there are several containers of just powder and there has been a few addition's to the place before I bought it

On 2018-01-31 18:53:25.097105 by (mod) -

Susan,

No one would expect a home appliance made in 2017 to contain asbestos

On 2018-01-30 01:43:36.079094 by Susan Holland

Is there asbestos in a 2017 Kennmore dryer? I opened the back a d found chunks of white material around the air duct

On 2016-11-03 18:25:15.618991 by Michelle

Hi, we have an original 1978 HVAC system with the transite pipe in two story home and we need to put in a new gas furnace. A friend that does HVAC suggested that one way to remedy the problem is to run a 2" pipe through the existing transite so we dont have to dispose or modify it. i realize this is probably not standard or to code, but is it a safe/effective solution?

On 2016-11-03 17:27:19.054939 by John B

Can I use my transite flue box for my new boiler?

On 2016-09-02 21:38:13.373186 by (mod) -

Yep, Chris there are certainly folks selling duct lining systems as a nice magic bullet alternative to replacing damaged HVAC ducts. Of course nobody can actually see how effective the liner is after its installation and during its life. In at least some installations I'm concerned about a reliner that simply falls off, exacerbating the IAQ problems without any warning whatsoever. What does the warranty include? Cost for damages, IAQ issues, testing, replacement, indoor cleaning of debris? I'd expect something more limited.

On 2016-09-01 16:33:51.634575 by Chris Carlisle

Duct Armor is a duct lining product that has been tested and approved for encapsulation of asbestos contained in duct work. Duct Armor can encapsulate and completely seal in slab duct work in 1 day without any intrusive construction to the home. The homeowner can begin to use their heat/air as soon as the process is completed and the liner carries a 15 year warranty.

On 2015-11-16 00:32:39.190909 by (mod) -

In the article above you will see reference to a companion article titled

Slab ductwork

That's what you want to read.

There we discuss the best methods for abandoning in slab duct work such as the one about which you asked.

On 2015-11-15 by Anonymous

What do I use to seal them to never be used again...

...

Continue reading  at TRANSITE PIPE AIR DUCT ASBESTOS RISK - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see

Recommended Articles

• ASBESTOS CEMENT PRODUCTS - topic home, where we include research on the chrysotile asbestos content & hazard of asbestos cement & transite products.
• ASBESTOS DUCTS, HVAC - Guide to Identification of Asbestos Materials On or In Heating and Cooling Duct Work: carbon monoxide hazards of transite chimneys and vents
• ASBESTOS IDENTIFICATION in BUILDINGS - Asbestos Identification in buildings: How to find & identify asbestos-containing materials
• CEMENT ASBESTOS PIPE MANUFACTURE
• ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY - Environmental Hazard Detection, Testing, Repair, Illness, Symptoms, & Prevention in buildings
• SLAB DUCTWORK
• TRANSITE ASBESTOS CHIMNEYS, DUCTS, PIPES
• TRANSITE PIPE AIR DUCT ASBESTOS RISK
• TRANSITE PIPE CHIMNEYS & FLUES - Guide to Identifying Asbestos Transite Chimneys & Flues & their Hazards in buildings
• TRANSITE PIPE WATER SUPPLY PIPING - Guide to Identifying Asbestos Cement Transite Water Pipes & their Hazards in buildings
• TRANSITE WATER SEWER PIPE ASBESTOS RISK
• WET CORRODED DUCT WORK

Also see Micro-Photographs of Dust from the World Trade Center collapse following the 9/11/01 attack.

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