InspectAPedia.com InspectAPedia®
 

Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair

Ask a Question or Search InspectAPedia

  • HOME
  • AIR CONDITIONING
  • ELECTRICAL
  • EXTERIORS
  • HEATING
  • HOME INSPECTION
  • INTERIORS
  • PLUMBING
  • ROOFING
  • SEPTIC SYSTEMS
  • STRUCTURE
  • WATER SUPPLY
  • ENERGY SAVINGS
  • ENVIRONMENT
  • INDOOR AIR IAQ
  • INSULATION
  • MOLD INSPECT TEST REMOVE
  • NOISE
  • ODORS
  • SOLAR ENERGY
  • VENTILATION
  • EXPERTS DIRECTORY
  • CONTACT US


Mobile Phone/PDA website viewMobile View
AIR CONDITIONING & HEAT PUMP SYSTEMS

A/C - HEAT PUMP CONTROLS & SWITCHES
A/C DATA TAGS
A/C - HEAT PUMP CRITICAL DEFECTS
A/C DIAGNOSTIC FAQs
A/C REFRIGERANTS
A/C TYPES, ENERGY SOURCES

AGE of AIR CONDITIONERS & HEAT PUMPS
AGE of HEATERS, BOILERS, FURNACES
AGE of WATER HEATERS
AIR CONDITIONER BTU CHART
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR CONDITIONER NOT WORKING

AIR FILTERS for HVAC SYSTEMS

AIR HANDLER / BLOWER UNITS
ANIMAL ALLERGENS / PET DANDER
ANIMAL ENTRY POINTS in buildings
ANIMAL ODORS IN buildings
APPLIANCE EFFICIENCY RATINGS
ASBESTOS IDENTIFICATION IN buildings

BACKUP HEAT for HEAT PUMPS

BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING

BOOKSTORE - Air Conditioning "How To" Books

CAPACITORS for HARD STARTING MOTORS
CAPILLARY TUBES
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
COMBUSTION GASES & PARTICLE HAZARDS

COMPRESSOR & CONDENSING COIL, A/C

CONDENSATE HANDLING, A/C
CLEANING & Legionella BACTERIA
DUCT SYSTEM & DUCT DEFECTS
  AIR FILTERS for HVAC SYSTEMS
  ALLOY SYSTEMS FLEXDUCT
  ASBESTOS HVAC DUCTS
  ASBESTOS PAPER on DUCTWORK
  ASBESTOS TRANSITE DUCTWORK
  BALANCING AIR DUCT FLOW
  DUCT & AIR HANDLER ODORS
  DUCT DAMAGE, MECHANICAL
  DUCT INSULATION - Asbestos Paper
  DUCT ROUTING & SUPPORT
  DUST CONTAMINATION FROM HVAC?
  FIBERGLASS DUCT, RIGID CONSTRUCTION
  FIBERGLASS HVAC DUCTS
  FIRE DAMPERS in DUCTWORK
  FLOOD DAMAGE in DUCT WORK
  GOODMAN GRAY FLEXDUCT
  INCREASING RETURN AIR
  LEAKY DUCT CONNECTIONS
  LOCATION OF REGISTERS & DUCTS
  MOLD in AIR HANDLERS & DUCT WORK
  NOISES in DUCT SYSTEM
  ODORS in AIR HANDLERS & DUCT WORK
  OWENS CORNING FLEXDUCT
  OWL FLEXDUCT
  RETURN AIR REGISTERS & DUCTS
  SOUNDPROOFING for DUCTWORK
  SUPPLY DUCTS & REGISTERS
  TRANSITE PIPE AIR DUCTS
  UNDERSIZED RETURN DUCTS
  UNSAFE DUCT OPENINGS
  VIBRATION DAMPENERS
  WATER & ICE IN DUCT WORK
    Convection Condensate Leaks into Ductwork
    External Leaks into Ducts
    Flood-Exposed HVAC Ducts
  WET CORRODED DUCT WORK
  ZONE DAMPER CONTROLS

ENERGY SAVINGS in buildings
EVAPORATOR COIL or COOLING COIL
EVAPORATIVE COOLING SYSTEMS
EVAPORATOR COIL or COOLING COIL
EXPANSION VALVES, REFRIGERANT

FAN, AIR HANDLER BLOWER UNIT
FAN AUTO ON Thermostat Switch
FAN, COMPRESSOR/CONDENSER UNIT
FAN CONVECTOR HEATERS - HYDRONIC COILS
FAN LIMIT SWITCH
FAN NOISES

FURNACES WARM AIR HEATING SYSTEMS

GASES, EXPOSURE, TESTING
  Carbon Dioxide - CO2
  Carbon Monoxide - CO
  METHANE GAS SOURCES
GAS MEASUREMENT TOOLS
GAUGE, REFRIGERATION PRESSURE TEST

HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION

HEAT PUMPS
HEATING SMALL LOADS
HOUSEWRAP AIR & VAPOR BARRIERS

HUMIDITY LEVEL TARGET

INDOOR AIR QUALITY IMPROVEMENT GUIDE

INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS
LEED GREEN BUILDING CERTIFICATION

LOST COOLING CAPACITY

MANUALS & PARTS GUIDES - HVAC
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
MOLD INFORMATION CENTER

ODORS in AIR HANDLERS & DUCT WORK
OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES

NOISY AIR CONDITIONER / HEAT PUMP
NOISE / SOUND DIAGNOSIS & CURE

PORTABLE ROOM AIR CONDITIONERS
PRESSURE READINGS, REFRIGERANT

REPAIR GUIDE, AIR CONDITIONERS / HEAT PUMPS
REPAIR & DIAGNOSTIC FAQs for A/C

REFRIGERANTS
RETROFIT SIZING for A/C or HEAT PUMPS

SEER RATINGS & OTHER DEFINITIONS

SOLAR ENERGY SYSTEMS

SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS
SWAMP COOLERS
SYSTEM OPERATION

THERMOSTATS, HEATING / COOLING

THERMOSTATIC EXPANSION VALVES

WATER COOLED AIR CONDITIONERS

More Information

Photograph of rusty air conditioning duct register

Wet or Corroded Heating or Cooling Ducts, Causes, Health Concerns, Repairs
InspectAPedia®  -         

  • Cause, Effects, & Prevention of Corrosion in HVAC Ducts
  • Health Risks from Wet Air Conditioning or Heating Ducts
  • Duct installation defects, safety hazards
InspectAPedia 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/Contact.htm.

This chapter of "How to Inspect the Central Air Conditioning or Cooling System" describes Wet or Corroded Heating & Cooling Ducts: Cause, Health Concerns,& Repairs to correct this condition. Rusty metal ducts or corroded HVAC ducts are an indicator of improper and possibly unhealthy conditions in the building as they are almost always associated with unwanted moisture in the duct system. Unwanted moisture in cooling ducts in particular, is an invitation to mold, bacterial, or other pathogens in the duct system and thus in the building air.

Readers should also see WATER & ICE IN DUCT WORK and see FROST BUILD-UP on AIR CONDITIONER COILS where we describe build-up of ice on the cooling coil in air conditioning air handler units. Also see TRANSITE PIPE AIR DUCTS where we describe flooding of HVAC ductwork in slabs. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.

This chapter continues with a discussion of corroded metal ducts and registers and associated health concerns. We point out and include photographs of locations where you can spot unwanted HVAC or cooling system moisture and rust, cite some related health concerns, and discuss ways to avoid duct corrosion or rust. We also offer advice on what to do about rusty ductwork. The master document, of which this is a chapter, describes the inspection of residential air conditioning systems (A/C systems) to inform home buyers, owners, and home inspectors of common cooling system defects.

CORRODED DUCT WORK - Corroded Air Conditioning Duct Work

Photograph of rusty air conditioning duct register Photograph of rusty air conditioning duct register

The photo at page top shows a very rusty air conditioning ductwork register, and a careful look into that system of metal duct work, found additional heavy rust in the duct system along with lots of debris. The photographs shown just above are of a less obviously rusty duct system and the rust stains on the vinyl floor suggest that the water in this duct system came from the floor level.

Are Rusty, Dirty Air Conditioning Ducts a Health Concern?

Not necessarily: To avoid inappropriate anxiety on the part of any readers we state up front that it is normal for some dust and debris to accumulate on the inside of heating or air conditioning ducts, and this material is not necessarily a hazard to building occupants. But when ducts have also been wet, or when ducts are constructed of materials like fiberglass insulation that have been damaged or can't be cleaned, some potential health or respiratory issues may be present, as we discuss further here.

Rust flakes from rusty heating or air conditioning ducts themselves are unlikely to be much of a health hazard - these particles are pretty big, not easily airborne, and probably won't be found at high levels in indoor air except in unusual circumstances. But rust in ducts is a problem indicator, showing quite clearly that the duct system has been wet.

The chief components of house dust, which will certainly collect within a duct system include fabric fibers and skin cells, often also including starch fragments and other organic debris. The combination of organic debris within a duct system and water (indicated by rusty ducts or duct registers) indicates a possible risk of mold or bacterial hazards within the air conditioning or heating system. Since blowing air through the system can pick up and distribute these hazards to occupants of the building, wet or previously-wet duct work is a potential health hazard to building occupants.

The actual health hazard level from wet or previously wet air conditioning or heating ducts in a building depends on:

  • The total area of duct or other surfaces that have been wet, including both duct system interior and the interior of the air handler or fan/blower unit and evaporator coil surface
  • The level of organic debris within the duct system
  • The materials used to insulate the duct interior: fiberglass and similar materials form a "sticky" surface that tends to hold debris and also to act as a sponge holding moisture, possibly increasing the risk of mold or bacterial hazards, and not easily cleaned.
  • The frequency of wet conditions: recurrent wetting obviously increases the risk of pathogens in the duct work, though we've seen significant contamination as a result of a single building flooding event which wet the ducts
  • The health vulnerability of individual occupants in the building: elderly, immune-impaired, asthmatics, infants, people with allergies, people with COPD or other respiratory illness, are more likely to be bothered sooner by duct contaminants that are produced by wet conditions in the air conditioning or heating system.

What To Do About Rusty HVAC Ducts, Wet or Previously Wet Fiberglass Ducts or Flex-Duct

Metal ducts that have been wet but are not severely damaged can and should be professionally cleaned. Be sure that the interior of the air handler is also inspected and cleaned.

Where you observe metal duct system components which are quite corroded, badly corroded materials should be replaced. This should not involve significant expense if only limited sections of readily-accessible duct work are involved.

Leaks into ducts routed through inaccessible building areas or cavities, and leaks into duct work which has insulation, particularly fiberglass insulation, in its interior, (typically fiberglass board), may harbor a mold colony, leading to both significant cleanup costs and potential health concerns.

Fiberglass-lined ducts or flex-ducts which have been wet should be inspected thoroughly, and sections which were wet and/or are particularly soiled should be replaced.

Questions & Answers regarding this article

.

Ask a Question or Search InspectAPedia

HTML Comment Box is loading comments...

Share this Article      

...

Technical Reviewers & References

  • InspectAPedia.com® - Daniel Friedman - Publisher & Editor.
  • InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
  • 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.

AIR CONDITIONING & HEAT PUMP SYSTEMS
AIR CONDITIONER COMPONENT PARTS
A/C - HEAT PUMP CONTROLS & SWITCHES
A/C - HEAT PUMP CRITICAL DEFECTS
A/C DIAGNOSTIC FAQs
A/C TYPES, ENERGY SOURCES
A/C REFRIGERANTS

AIR CONDITIONER BTU CHART
SEER RATINGS & OTHER DEFINITIONS
OPERATING COST
SYSTEM OPERATION
OPERATING TEMPERATURES
OPERATING DEFECTS
LOST COOLING CAPACITY
CHINESE DRYWALL HAZARDS
COMBUSTION GASES & PARTICLE HAZARDS
CONDENSATE HANDLING, A/C
CONDENSATION or SWEATING PIPES, TANKS
COMPRESSOR & CONDENSING COIL, A/C
AIR FILTERS for HVAC SYSTEMS

AIR HANDLER / BLOWER UNITS
ANIMAL ALLERGENS / PET DANDER
ANIMAL ENTRY POINTS in buildings
ANIMAL ODORS IN buildings
APPLIANCE EFFICIENCY RATINGS
ASBESTOS IDENTIFICATION IN buildings

BACKUP HEAT for HEAT PUMPS

BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING

BOOKSTORE - Air Conditioning "How To" Books

CAPACITORS for HARD STARTING MOTORS
CAPILLARY TUBES
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
COMBUSTION GASES & PARTICLE HAZARDS

COMPRESSOR & CONDENSING COIL, A/C

CONDENSATE HANDLING, A/C
BACKUP HEAT for HEAT PUMPS

BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING

BOOKSTORE - Air Conditioning "How To" Books

CAPACITORS for HARD STARTING MOTORS
CAPILLARY TUBES
CLEANING & Legionella BACTERIA
DUCT SYSTEM & DUCT DEFECTS
  AIR FILTERS for HVAC SYSTEMS
  ALLOY SYSTEMS FLEXDUCT
  ASBESTOS HVAC DUCTS
  ASBESTOS PAPER on DUCTWORK
  ASBESTOS TRANSITE DUCTWORK
  BALANCING AIR DUCT FLOW
  DUCT & AIR HANDLER ODORS
  DUCT DAMAGE, MECHANICAL
  DUCT INSULATION - Asbestos Paper
  DUCT ROUTING & SUPPORT
  DUST CONTAMINATION FROM HVAC?
  FIBERGLASS DUCT, RIGID CONSTRUCTION
  FIBERGLASS HVAC DUCTS
  FIRE DAMPERS in DUCTWORK
  FLOOD DAMAGE in DUCT WORK
  GOODMAN GRAY FLEXDUCT
  INCREASING RETURN AIR
  LEAKY DUCT CONNECTIONS
  LOCATION OF REGISTERS & DUCTS
  MOLD in AIR HANDLERS & DUCT WORK
  NOISES in DUCT SYSTEM
  ODORS in AIR HANDLERS & DUCT WORK
  OWENS CORNING FLEXDUCT
  OWL FLEXDUCT
  RETURN AIR REGISTERS & DUCTS
  SOUNDPROOFING for DUCTWORK
  SUPPLY DUCTS & REGISTERS
  TRANSITE PIPE AIR DUCTS
  UNDERSIZED RETURN DUCTS
  UNSAFE DUCT OPENINGS
  VIBRATION DAMPENERS
  WATER & ICE IN DUCT WORK
    Convection Condensate Leaks into Ductwork
    External Leaks into Ducts
    Flood-Exposed HVAC Ducts
  WET CORRODED DUCT WORK
  ZONE DAMPER CONTROLS

ENERGY SAVINGS in buildings
EVAPORATOR COIL or COOLING COIL
EVAPORATIVE COOLING SYSTEMS
EVAPORATOR COIL or COOLING COIL
EXPANSION VALVES, REFRIGERANT

FAN, AIR HANDLER BLOWER UNIT
FAN AUTO ON Thermostat Switch
A/C REFRIGERANTS
A/C - HEAT PUMP CRITICAL DEFECTS
A/C DIAGNOSTIC FAQs
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS

FURNACES WARM AIR HEATING SYSTEMS
INDOOR AIR QUALITY IMPROVEMENT GUIDE

  • 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.
  • Air Diffusion Council, 1901 N. Roselle Road, Suite 800, Schaumburg, Illinois 60195, Tel: (847) 706-6750, Fax: (847) 706-6751 - info@flexibleduct.org - www.flexibleduct.org/ -
    "The ADC has produced the 4th Edition of the Flexible Duct Performance & Installation Standards (a 28-page manual) for use and reference by designers, architects, engineers, contractors, installers and users for evaluating, selecting, specifying and properly installing flexible duct in heating and air conditioning systems.
    Features covered in depth include: descriptions of typical styles, characteristics and requirements, testing, listing, reporting, certifying, packaging and product marking.
    Guidelines for proper installation are treated and illustrated in depth, featuring connections, splices and proper support methods for flexible duct. A single and uniform method of making end connections and splices is graphically presented for both non-metallic and metallic with plain ends."
    The printed manual is available in English only. Downloadable PDF is available in English and Spanish. 
  • Owens Corning Duct Solutions - www.owenscorning.com/ductsolutions/ - provides current HVAC ductwork and duct insulating product descriptions and a dealer locator. Owens Corning Insulating Systems, LLC, One Owens Corning Parkway, Toledo, OH 43659 1-800-GET-PINK™
  • "Flexible Duct Media Fiberglas™ Insulation, Product Data Sheet", Owens Corning - see owenscorning.com/quietzone/pdfs/QZFlexible_DataSheet.pdf
    "Owens Corning Flexible Duct Media Insulation is a lightweight, flexible, resilient thermal and acoustical insulation made of inorganic glass fibers bonded with a thermosetting resin."

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

  • Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
  • Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.
  • Home Reference Book - Carson Dunlop The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
  • Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
  • Principles of Refrigeration, R. Warren Marsh, C. Thomas Olivo, Delmar Publishers, 1979
  • "Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
  • Refrigeration and Air Conditioning Technology, 5th Ed., William C. Whitman, William M. Johnson, John Tomczyk, Cengage Learning, 2005, ISBN 1401837654, 9781401837655 1324 pages
  • 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.).
  • Air Conditioning Inspection, Diagnosis, Repair, Efficiency all the basics for home owners, inspectors, new repairmen
  • NewAir Conditioning SEER - New DOE Air Conditioner and Heat Pump Efficiency Standard
  • Asbestos HVAC Ducts and Flues field identification photos and guide
  • Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation
  • ...
  • Home About Us Accuracy Contact Us Content Use Policy Privacy Website Description © 2012 Copyright InspectAPedia.com