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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
HVAC Duct odor diagnosis & cure: This article explains the diagnosis and cure of odors in HVAC ducts, air handlers, blowers, for both warm air heating and air conditioning systems. Duct and air handler odors in buildings can be traced to a variety of sources such as leaks and mold in the duct system, a leaky (and unsafe) heat exchanger sending flue gases or even carbon monoxide into building air (see CARBON MONOXIDE - CO and HEAT EXCHANGER LEAKS), dead animals in the ducts or air handler, or even a bad blower motor that is overheating.
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Building Air Duct and Air Handler Odor Guide: How to Find, Test, & Remove Odors, Odor Detection, Smells, & Gases that Appear in Ductwork
This website provides articles on to diagnose, test, identify, and cure or remove a wide range of obnoxious or even toxic odors in buildings and in building water supply. We discuss odors from a variety of sources including animals including pets, dogs, cats, or unwanted animals or dead animals, formaldehyde odors in buildings from building products or furnishings, plumbing drains, plastic or vinyl odors from building products, flue gases, oil tanks or oil spills, pesticides, septic odors, sewer gases, and even abandoned chemicals at properties.
Readers should see our more extensive odor diagnosis home page: ODORS, Smells, Gases in buildings-Diagnosis & Cure. Also see OIL HEAT ODORS & NOISES, as well as OIL BURNER NOISE SMOKE ODORS. Readers should also see our ODOR DIAGNOSIS CHECKLIST, PROCEDURE for a quick check that can help identify the source of smells in buildings and see SMELL PATCH TEST to Track Down Odors.
Tracking down building odors associated with the heating or cooling ductwork can be tricky not only because there is a larger variety of possible sources of duct smells and stinky ducts than you might guess, but also because once an odor source has invaded the HVAC system, smells can be delivered to other more remote building areas.
One IAQ investigator associate traced the mold-related-illness of a building occupant to the delivery of mold-contaminated air (MVOC's and mold spores) right to the occupant's head when she was asleep - a supply air register was close to the bed's headboard.
The checklist below addresses things to check if odors appear to be present in or coming from building heating or cooling ductwork, air handlers, or blower compartments, or at the heat exchanger.
Frequently Asked Questions (FAQs) About Odors in or From Heating & Air Conditioning Air Duct Systems
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Question: foul odor coming from in-slab HVAC Ducts - how do we fill in the ducts
We have had our furnace duct work moved to the attic to eliminate the foul odor coming from the in slab duct work. It is still coming in to the house and we need to fill all the duct work with something that will seal off the system. Can we have all of the ducts filled solid with spray insulation foam to correct this. The odor is making my wife and I Ill. She is allergic to mold & mildew also! Please advise! Thank You Tom - 3/12/2012
Tom, SLAB DUCTWORK - catalogs the functional and environmental problems found when HVAC air ducts are routed in or below floor slabs IN my experience, if we seal the air supply and return registers for the in-slab duct system we don't expect to find odors coming from the remaining ductwork. But if you are sure that you need a more thorough fill-in, I would consider pouring concrete in the entire duct system - that material will fill the in-floor ducts completely, eliminating any concern for stagnant water, rodents, etc.
(By the way, there is no mildew in buildings - mildew only grows on living plants. If you smell "mildew" inside a building, it's some other genera/species of mold.)
Question: puff of smoke with A/C on is drawn into ductwork
A/C on, doors closed, in the desert. Light, puff, smoke. For 4 years. It Draws into ductwork, & exchanger, paint,& clean all you want. When it gets warm, & the A/c goes on, the house will stink of smoke. - DD 8/8/2012
Watch out: an air conditioner has absolutely no business emanating a puff of smoke during any part of its operating cycle. This sounds dangerous. You need a service call by an expert.
I have a forced air oil furnace. It began putting strong fumes into the house just before and during shut down of a cycle.
There was no c02 detected in the home. I had multiple HVAC companies inspect the furnace, the problem continued. To the point that windows had to be left open, the family was suffering respiratory distress.
I had the furnace replaced. I had the chimneys cleaned. I had the vents cleaned. The problem continues. The HVAC company is stumped, they say there would be co2 present, yet they confirm they smell odor. To me, it's the same as car exhaust.
The chimney cleaning company said if I continue to have problems, they can install an insert into the chimney. ? The HVAC company wants to install an electronic whole house air filter and if that does not resolve the issue, they will put in an electric furnace and heat pump.
This is becoming a very expensive and I'm afraid health risk issue. Two furnaces with the same issue?
Thanks for any advice. - D.M., Chardon OH
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem with a heating system - it sounds from your description as if perhaps your onsite people lacked that expertise or perhaps did not accurately understand your heating system odor complaint. That said, here are some things to consider:
Questions & answers or comments about the causes of & cures for HVAC duct system odors & smells.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.