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AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C - HEAT PUMP CONTROLS & SWITCHES
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR FILTER EFFICIENCY
AIR FILTERS, FIBERGLASS PARTICLES
AIR FLOW MEASUREMENT CFM
APPLIANCE EFFICIENCY RATINGS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
DEFINITION of Heating & Cooling Terms
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM & DUCT DEFECTS
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATIVE COOLING SYSTEMS
FAN LIMIT SWITCH
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
LOW VOLTAGE TRANSFORMER TEST
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
OPERATING COST, AIR CONDITIONER
OPERATING DEFECTS, AIR CONDITIONING
REPAIR GUIDES A/C / HEAT PUMP
REPAIR & DIAGNOSTIC FAQs for A/C
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
Asbestos in or on HVAC ducts (air ducts or heating and cooling ductwork) or inside the air handler (blower unit) itself is a possible hazard for which we provide information, photos, & links to additional documents. This article shows how to recognize asbestos materials in heating and air conditioning ducts, vibration dampers, chimneys, and flues, and air handlers or blower compartments, 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 our article series that describes the inspection of residential air conditioning systems (A/C systems) to inform home buyers, owners, and home inspectors of common cooling system defects.
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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.
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 AIR 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.
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:
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.
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.
Asbestos in the Air Handler of Furnaces or Air Conditioners
Among asbestos products used in heating or air conditioning air handlers and blowers, we suspect that VIBRATION DAMPENERS, especially in undamaged condition, are likely to release much lower levels of asbestos particles into the HVAC system air than the softer insulating materials found in some air handlers themselves.
We have observed friable asbestos inside older warm air heating furnaces made by Williamson (corrugated asbestos paper insulation inside the air handler of an older unit) and by Armstrong (asbestos insulation around the flue vent connector passage through the air handler's blower compartment side wall - photo shown at left), and in some other brands of heating equipment.
But in our OPINION even in the air handler, depending on the size or amount, condition (undamaged), and location, the release into building air of asbestos from these sources may be very difficult to detect - suggesting that in those cases it is at very low levels, below measurable effect.
Also see these articles on asbestos in buildings
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Frequently Asked Questions (FAQs) about asbestos materials on HVAC Ductwork
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Question: can I cover tears in asbestos water pipe wrap
I believe I have asbestos wrap covering my water pipes and heating duct work in my 1950's home. The wrap is in good shape, with the exception of a few tears here and there. The article says to leave it alone if possible.
Can I cover these tears myself to avoid airborne contamination with say a piece of duct tape and to avoid having to do total removal, which will probably present a greater health risk? I have a home gym down there and I am very concerned about the health risk especially since I run a fan sometimes. thanks - Diane 6/12/12
Diane there are several procedures that professionals use to cover intact asbestos or presumed-asbestos pipe insulation; in addition to professionally sprayed encapsulants, we've seen good-condition pipe insulation that was simply spray-painted to form a harder skin and to bind any few loose surface particles; other encapsulators wrap the existing insulation with a new plastic or fiberglass covering.
Certainly I would not run a fan in a location that might distribute asbestos-suspect particles. And if there is evidence that the material has been disturbed or damaged in the past, even in small areas, damp wiping and HEPA vacuuming of the area surfaces might be appropriate both to remove suspect dust and to avoid distributing it when you later do run a fan of any sort.
Question: 1960 Sears Wall Furnace with corrugated asbestos paper insulation in the air handler
We have an older Sears wall furnace from about 1960 with the corrugated asbestos paper inside the air handler as you mentioned. Two years ago, the paper fell off its mount and lodged about an inch below the top of the exhaust grating, in the top few rows of holes. We continued to use the furnace for the rest of that season, but haven't used it since. I'm curious if you feel this was a serious contamination risk (we've heard people say both possibilities) and if you have any suggestions about removal of the furnace or simply the asbestos paper. Unfortunately, the furnace is in the middle of an open floor plan and will be very difficult to isolate from the rest of the house - Tim 9/28/12
Tim I really can't assess the asbestos risk by just an email; one would need to inspect the system, perhaps performing some tests of nearby dust in the ductwork. While one would be inclined from just your message information to advise against getting too excited, if the paper was in poor enough condition to fall apart, no one is going to bet their mortgage, kids education and car on assuring you that there was no risk of contamination.
The real flies in the ointment are the risk of having blown asbestos dust through a building's occupied space IF there was friable damaged asbestos anywhere in the air path - in that case test building settled dust, an approach that looks more thoroughly than just a momentary air test - and second, even if you removed the asbestos material from the furnace, when you seek to replace it with something suitable, again, nobody is going to be willing to accept responsibility for the safety of the results.
Unfortunately what this has led to for the furnaces I've found that had asbestos built into the plenum and air path has been:
Question: 1960 house with musty smell found black & yellow board insulation
I have a house that was built in 1960. We bought it about a year ago and it has a musky smell. Well this lead us to see what it looked like inside the ducts and heat pump. In the intake ducts it has this board type insulation that's black and yellow. Also inside the heat pump it has insulation where the coil and blower is. Would there be a chance this insulation could be asbestos? It looks like it has been deteriorating for years which means we have been breathing this stuff. Im concern for my 2 year old. - Angela 10/7/2012
Black and yellow fiberglass board insulation is not fiberglass, though if it's in poor condition you may have been blowing irritating fiberglass particles into the building air. A check of settled dust and of air might give an idea of how much dust there is and whether or not a clean-up is justified. See FIBERGLASS HAZARDS for details.
Question: Asbestos was removed from our home but we're worried that the ducts were not cleaned
We have just finished having our asbestos professionally removed from our house. However, my husband looked in the furnace and ducts and they were not cleaned at the time of the abatement. We have entered the house a couple of times, are we at risk?? - Erin 11/18/12
Question: how do I distinguish between asbestos & non-asbestos paper tape sealant on HVAC ducts?
Below someone said he had the "pale paper-like tape" tested and it turned out to be cellulose. I wonder: How do I get the material tested?
Jem & Ken Ray:
For very small amounts of asbestos-suspect material it may make more sense to just treat the material as Presumed Asbestos Containing Material (PACM) rather than face the time delay and lab costs for tiny sample testing.
Appearance of Non-Asbestos paper tape seam sealers & coverings for HVAC ducts
There are paper like tape seams that do not contain asbestos - usually we see rectangular-grid spaced reinforcing fibers in the newer tapes;
Appearance of asbestos-paper tape seam sealants & duct coverings
Take a look at how the tape has been adhered to the surface it is covering. Asbestos paper or paper tape strips used on duct seams and on some pipe joints was wet and then applied in strips to seal both metal HVAC ductwork exteriors and to cover some asbestos pipe joints.
You won't (at least in my field experience) see fiberglass reinforcing seams in asbestos paper tape, and the asbestos-based paper tape may be uniformly dimpled over its surface from rolling in the mill.
Questions & answers or comments about asbestos materials on or inside of heating or air conditioning air ducts.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.