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This article shows how to recognize asbestos materials in heating and air conditioning ducts, vibration dampers, chimneys, and flues, and it identifies potential asbestos fiber release or carbon monoxide hazards in buildings where certain asbestos and cement-asbestos transite pipe materials are used for ducts or for heating appliance chimneys and vents. This is part of a document which describes the inspection of residential air conditioning systems (A/C systems) to inform home buyers, owners, and home inspectors of common cooling system defects.

Asbestos in or on HVAC ducts (air ducts or heating and cooling ductwork) is a possible hazard for which we provide links to separate documents.

Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. © Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links 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.

Readers should also see:

• 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
• ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY - Environmental Hazard Detection, Testing, Repair, Illness, Symptoms, & Prevention in Buildings
• IDENTIFICATION of ASBESTOS in BUILDINGS - Asbestos Identification in Buildings: How to find & identify asbestos-containing materials
• Transite Pipe Air Ducts - Hazards of Asbestos-containing Transite Pipe HVAC Ducts: duct collapse, mold, radon, asbstos fiber release
• 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

Asbestos Materials on or in the Air Conditioning or Heating System Duct Work

This article describes the inspection of heating and air conditioning ducts for visual evidence of asbestos materials in or on HVAC ducts. The photograph shows asbestos paper heating duct wrap. Asbestos in these locations is a possible hazard which may require special attention. We also warn about signs of amateur asbestos removal which may merit additional testing and cleanup work.

If readers return to the first chapter or view the A/C chapter index, the major components of an air conditioning system are described, sketches and photographs are provided, and common defects for each component are listed along with visual or other clues that may suggest a problem or probable failure of A/C components.

Asbestos - Ductwork Safety Recommendation

Another example of asbestos duct wrap is shown in this photograph. During an inspection of the heating or air conditioning duct system and air handler, look for what may be asbestos containing insulating material on the heating system. Cement asbestos "millboard" used as a partial heat shield on wall/ceiling surfaces. White corrugated insulating material on and hanging from pipes, white paste material surrounding certain plumbing joints. White "paper" wrapped on outside of some heating ducts. White woven material used as flexible joint between some heating ducts. White woven material used as flexible joint in the vibration damper between air handler the duct work.

TRANSITE and SONNO-DUCT Air Conditioning or Heating Duct Material Warnings: asbestos fiber release and carbon monoxide hazards

Caution: Down flow furnace in building with concrete slab and with perimeter duct work raises questions: what is the duct work made of ? Is asbestos material found right in the air pathway in a building? If so there are higher risks of airborne asbestos contamination in that building than otherwise.

Transite chimney Carbon Monoxide Hazards: where used for chimneys in buildings, transite pipe may form a very serious, potentially fatal carbon monoxide hazard due to chimney blockage. We explain how and why the carbon monoxide poisoning hazard develops in our article at Transite Pipes, Chimneys & Flues.

Transite Duct Asbestos Hazards: if used for air ducts transite pipe may be a an asbestos hazard, particularly where the ducts become softened by water exposure (such as air ducts located in floor slabs), potentially releasing asbestos fibers into the building air. See Transite Pipe HVAC Ducts for details.

Sonno Duct (spun composition material) may have absorbed water, collapsed, and be blocking the duct line and potentially inviting a termite infestation or a mold contamination problem in the building.

More identification photographs of transite pipe in buildings can be found at Asbestos Transite Chimneys & Flues and at Transite Pipe HVAC Ducts

ASBESTOS RISKS - on Heating and Cooling Ducts

While there may be no conclusive data nor studies which evaluate hazards regarding presence of this material in residential buildings, it is generally considered by the scientific community to be a potential health risk.

Asbestos heating system insulation is also a potential economic risk as future buyers may be concerned about this material. Disposal costs for this material are increasing.

Depending on condition and location of asbestos material, treatment ranges from doing nothing to complete removal. Removal could involve significant costs.

You should obtain proper technical information and health and safety guidelines before attempting to do anything with this material. It is the breathing of fibers when this material is disturbed, not it's mere presence, which is considered a health risk. When the material is not found in living areas in poor condition treatment is not usually an emergency and you have ample time to become informed, obtain estimates, and select a course of action.

[Offline text files of additional advice for insertion into home inspection reports where asbestos material is observed:
... HEAT.036 - Asbestos - Lab Test Requested (file of inspection report text recommendation)
... HEAT.031 - Asbestos - material unconfirmed; choice of treatment affects. costs
]

If the asbestos-suspect material seen in a building is confirmed as actual asbestos or an asbestos-containing product, depending on its condition and location, treatment ranges from doing nothing to complete removal.

Professional asbestos removal would involve significant costs and is the recommended course of action where asbestos materials are damaged, friable, in a location subject to damage, in an occupied space, and/or in an unoccupied location where asbestos debris is likely to be carried into occupied space by human traffic or by the operation of heating and cooling equipment.

A number of asbestos treatment options are available where asbestos material is found in a building. Choice of treatment can make a big difference in possible costs of handling the material. You should obtain proper technical information and health and safety guidelines before attempting to do anything with this material.

Asbestos Warning: incomplete removal, amateur workmanship on the Air Conditioning or Heating System

The following is an example of building or home inspection report language when the inspector detects evidence of improper, incomplete, or amateur "asbestos remediation" efforts in a building.

Amateur removal of asbestos from a building can create very serious health and cost concerns because of the possibility that the amateur cross-contaminated other building areas with asbestos debris and also because of the possibility that the asbestos products that were removed were disposed of improperly. we have on occasion found "removed" asbestos insulation simply disposed of by dumping it on the same property or stuffing it into a crawl space or attic.

Improper/Incomplete Asbestos Duct Insulation or Pipe Wrap Removal: Caution: When we observe that a considerable amount of this insulating material has been removed leaving scraps or remainders and without cleaning and sealing of the exposed ducts or piping, we issue the following warning:

Asbestos duct or piping insulation removal has not followed approved methods and procedures: we saw that HVAC duct work or piping has not been cleaned nor sealed, and that the suspect material has been left in some places - details not found when materials were removed by trained professionals.

Unprofessional removal of controversial materials in a building may raise health, legal, or marketing concerns for future property owners. You should attempt to obtain documentation regarding who did what to the property regarding this topic. Additional testing to assure that no hazards or legal issues remain, may involve significant expense. expense; possible, hazardous materials.

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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.

AIR CONDITIONING & HEAT PUMP SYSTEMS
AIR CONDITIONER COMPONENT PARTS
CONTROLS & SWITCHES
A/C TYPES, ENERGY SOURCES
RATED COOLING CAPACITY
AIR CONDITIONER BTU CHART
SEER RATINGS & OTHER DEFINITIONS
OPERATING COST
SYSTEM OPERATION
OPERATING TEMPERATURES
OPERATING DEFECTS
LOST COOLING CAPACITY
COMPRESSOR & CONDENSING COIL
AIR HANDLER UNIT
AIR FILTERS for HVAC SYSTEMS
CONDENSATE HANDLING
DUCT SYSTEM DEFECTS
  ASBESTOS HVAC DUCTS
  DUCT ROUTING & SUPPORT
  BALANCING AIR DUCT FLOW
  FIBERGLASS HVAC DUCTS
  FIRE DAMPERS in DUCTWORK
  GOODMAN GRAY FLEXDUCT
  INCREASING RETURN AIR
  LEAKY DUCT CONNECTIONS
  LOCATION OF REGISTERS & DUCTS
  OWENS CORNING FLEXDUCT
  OWL FLEXDUCT
  RETURN AIR REGISTERS & DUCTS
  SUPPLY REGISTERS, & ZONES
  Transite Pipe HVAC Ducts
  UNDERSIZED RETURN DUCTS
  UNSAFE DUCT OPENINGS
  VIBRATION DAMPERS
  WATER & ICE IN DUCT WORK
  WET CORRODED DUCT WORK
  ZONE DAMPER CONTROLS
FAN AUTO ON CONTROLS
A/C REFRIGERANTS
A/C DIAGNOSTIC FAQs
CRITICAL DEFECTS
FURNACES WARM AIR HEATING SYSTEMS

• Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects" section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and home inspection educator.
• Thanks to Jon Bolton, an ASHI, FABI, and otherwise certified Florida home inspector who provided photos of failing Goodman gray flex duct in a hot attic.
• Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).

More Information on Building Diagnostic Inspections and Repairs

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For more information about fiberglass as an indoor air quality concern see:

• Fiberglass in Indoor Air, HVAC Ducts, and Building Insulation
• Fiberglass Particle Identification in the Fiberglass Test Laboratory
• Goodman Gray Flex Duct Deterioration and Failures
• Mold in Fiberglass Insulation
• Optimum Indoor Air Filters
• Owens Corning Flex Duct Deterioration and Failures
• World Trade Center Dust Particle Identification

For more information about asbestos as an indoor air quality concern with focus on easy ways to identify asbestos materials in buildings, see:

• Asbestos Identification in Buildings: How to find & identify asbestos-containing materials
• Asbestos in Good Condition
• Asbestos HVAC Ducts - Asbestos Materials On or In Heating and Cooling Duct Work
• Asbestos paper duct wrap
• Asbestos Transite Chimneys, Flues, & Pipes in Buildings
• Asbestos under the microscope
• Asbestos Vibration Dampers & Asbestos in the Air Handler
• Ceiling tiles: How to recognize ceiling tiles that may contain asbestos
• Examples of unusual uses of asbestos in buildings

• Asbestos: How to find and recognize asbestos in Buildings - visual inspection methods, list of common asbestos-containing materials
• Asbestos HVAC Ducts and Flues field identification photos and guide
• 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.

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