Hazards of Asbestos-containing Transite Pipe HVAC Ducts InspectAPedia® -
Safety hazards associated with cement asbestos transite pipe heating or air conditioning ducts: asbestos fiber release, duct collapse, bacterial & mold contamination, radon gas entry.
How to recognize asbestos transite pipe in buildings
Our site offers impartial, unbiased advice without conflicts of interest.
We will block advertisements which we discover or readers inform us are associated with bad business practices,
false-advertising, or junk science. Our contact info is at
InspectAPedia.com/appointment.htm.
This page discusses 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, an asbestos-cement product, was used for HVAC ducts and for chimney or flue material to vent gas-fired appliances.
Cement-asbestos transite pipe may also have been used for water piping in some communities.
This document assists building buyers, owners or inspectors who need to identify asbestos materials (or probable-asbestos) in buildings by simple
visual inspection.
Transite air ducts in slabs often collect water, mold, pathogens. 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. The photo (above-left) of a sewer line routed immediately below a transite asbestos in-slab floor heating duct was provided courtesy of reader Conrad.
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 or water 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.
Readers concerned with ice or water leaks into or out of HVAC ductwork should also see WET CORRODED DUCT WORK and see WATER & ICE IN DUCT WORK as well as FROST BUILD-UP where we discuss build-up of ice on the cooling coil in air conditioning air handler units.
ASBESTOS HVAC DUCTS - Guide to Identification of Asbestos Materials On or In Heating and Cooling Duct Work: carbon monoxide hazards of transite chimneys and vents
Also see Micro-Photographs of Dust from the World Trade Center collapse following the
9/11/01 attack. Links to U.S. government and other authoritative research and advice are included.
[Page top photo of transite duct material courtesy of Thomas Hauswirth, a Connecticut home inspector.
TRANSITE PIPE HVAC DUCTS - Asbestos Heating or Air Conditioning Duct Material Warnings
Transite pipe, which contains significant percentage of asbestos fibers, was often used for heating ducts and on occasion heating
and cooling ducts in older buildings.
The transite pipe was used in a buried-in-slab construction methods which placed
the transite piping below or in a building floor slab. Asbestos-containing transite pipe HVAC ducts were also used
in exposed areas such as shown in the crawl space photograph at the top of this page.
Transite Duct Asbestos Warnings & Hazard Details
Transite ducts used for HVAC air flow, especially when used buried in building
concrete floors or slabs, may break, collapse, leak water in (forming a mold and bacterial reservoir in the HVAC system,
or may release asbestos and other particles in building air when the HVAC system is operating.
An up-flow or down flow furnace in a building with concrete slab and with perimeter duct work
raises some important health and cost questions:
The photograph above shows a transite cement asbestos heating duct in a carpeted floor slab.
We recommend that in-slab heating or air conditioning ducts made of transite be sealed and abandoned, and alternate heat sources installed. This improvement
removes an asbestos hazard, a flooded duct and mold hazard, and in some locales, also a radon gas entry point.
The photograph shows the edges as well as surface of the transite material. Transite pipe
HVAC ducts get quite dirty and are not always easy to identify. [Photo and comments on transite in-slab HVAC ducts
courtesy of Roger Hankey, a Minnesota home inspector.]
Asbestos hazards of transite ducts: Cementious duct material may contain asbestos. What is this "cement"
duct work made of Cement and asbestos fibers.
How much asbestos is in Transite pipe? While it's cementious, transite ducts or even transite pipe used
for heating flue vents is a potential asbestos hazard in buildings. Transite pipe typically contains about
15% to 25% asbestos fibers, typically fibrous chrysotile asbestos.
A careful asbestos testing lab may report both fibrous and fragmented
asbestos which can occur in still smaller pieces (thus more easily remaining airborne and increasing human exposure to asbestos).
The balance will be cement and possibly other fibers or binders. If transite pipe is damaged or is cut mechanically (such as by using power equipment), friable, airborne asbestos fibers may
be generated - a health and costly cleanup concern.
Air quality hazards of in-slab duct systems: include water leaks into the duct system which can in turn generate a
mold or bacterial hazard or can cause softening, collapse, and blockage of the in-slab transite pipe duct.
While there are companies offering duct cleaning and duct sealing services, we remain cautious
that such a "sealing" project creates a false sense of confidence that no remaining duct issues exist, causing the
occupants to miss the discovery of future leaks and in-duct problems.
Radon entry through in-slab duct systems: can occur in areas where radon is present at problem levels in the soils.
In particular, because a return air duct is often at negative pressure (when the blower is operating), the movement of radon
gas from the soil into the building air through a leaky in-slab duct can be significant, certainly greater than the movement
into the building from other openings such as through a basement slab crack.
Sewer Gas entry into the HVAC duct system through in-slab transite asbestos ductwork: as reader Conrad discovered while tracking down the odor of sewer gas that was appearing in a home's in-slab ductwork, placing in-slab ducts close to sewer piping (or septic system piping) invites any future sewer gases leaking out of the pipingright into the HVAC duct system.
The owner tracked the sewer gas odor that was coming out of the building's heating ducts to a break in the sewer piping located in the same floor.
The repair of the sewer gas odor involved jack-hammering out the floor slab, removing and replacing the leaky cast iron sewer pipe, and repairing the floor. Because of the inconvenience and cost of relocating these air ducts or converting to an alternate heating distribution method, the owner elected to retain the transite in-slab floor ducts. Additional measures useful in tracking down the source of odors coming from duct work can be found at DUCT & AIR HANDLER ODORS.
Asbesos fiber release hazards during removal of demolition of transite piping are discussed at Transite Pipe Chimneys & Flues.
Incorrect spellings of transite asbestos piping or transite duct material that we've seen include transit pipe, transit ducts,
transite chimneys, transide pipe, transide ducts, and transight pipe or transight ducts. "Transite" is the correct spelling.
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Fiberglass: Indoor Air Quality Investigations: Health Concerns About Airborne Fiberglass: Fiberglass in Indoor Air from HVAC ducts, and Building Insulation
Enviro-Scare: Electric Power Lines, Electromagnetic Fields, Cancer Risk, & "Enviro-Scare" - The Normal Curve Cycle of Public Fear of Environmental Issues
Dust from the World Trade Center collapse following the 9/11/01 attack: the lower floors of this building contained spray-on fire-proofing asbestos materials.
Asbestos Information Links: Asbestos Detection, Testing, Recognition, Hazards, Field Photos, and Information Sources, including
health-related links such as legal services and information about mesothelioma and other cancers.
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
InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest.
The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.
InspectAPedia ® Home & Site Map 
InspectAPedia® Home & Site Map
