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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 DIAGNOSIS & REPAIR
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
FAN NOISES, HVAC
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, 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.
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.
HVAC Duct Odor Diagnosis & Cure: What to Do Next
Question: HVAC system odors when changing from cooling to heating mode - "Evergreen Smell"
I have another puzzle for you. Back in August 2013, we moved into this house. It is a 2-story house built in 1983. It has no basement and no crawl space. The day before we moved in, we had the air ducts cleaned and sanitized. We put the AC on and all was good for 2 months. The cooler temps came in October and we no longer needed the AC on. A few days went by with no AC or heat on because the house temp was good.
However, an evergreen smell started to enter into the ductwork. Yikes. I had handymen out, HVAC guys out, had my husband clean the evaporator coil, etc. We spent way to much time & money and were getting nowhere. Low & behold, the heat kicked in then and the evergreen odor was gone for several months. Unfortunately, the evergreen odor is back now that AC season is here. My husband cleaned the evaporator coil again. The odor is still there.
I checked with the previous owners, and they never used pan tablets which may explain the evergreen odor being in the ductwork and coil housing. I spoke to several HVAC companies, too. Honestly, it will be a total waste of money to have HVAC guys out because we have been there and done that. I need a different spin on this and how to fix it. The newest twist in this happened a few hours ago. I went to open the frig and smelled the evergreen odor in there. I thought I was having a nightmare.
I think I know what is causing the musty evergreen odor in our air ducts & coil. I think it is a slow freon leak. Call me crazy, but it is the only thing that makes sense right now to me. Go figure that the outside temp dropped from 75 degrees to 30 degrees. I need a warm outside temp in order to have an HVAC service come out to do the dye test for a possible freon leak. I just wish I could do something now to patch up the leak, so that the fumes will stop entering our house. The fumes are not serving our immune systems well around here. - S.N. 4/14/2014
Reply: refrigerants are generally odorless: look for odor source & odor transport
It may be obvious but worth saying, one would tackle the question by asking what's different between the two HVAC modes, then look closely at those details. The air is moving from and to the same places via the same fan and in the same ductwork, right? It's only heat vs cooling, temperatures, moistures that may be different - or something else different that's less obvious.
'Evergreen odors" sounds (smells) to me like an air freshener product or possibly a cleaning product someone has used somewhere. Refigerant gases are themselves odorless.
Thank you for your feedback. From all the research and feedback I am getting, it looks like freon travels outside during the winter. When it warms up, it travels inside the house. That would explain why the evergreen odor suddenly reappeared last week when the temp rose to 70 degrees. I just have to tackle finding the leak now and go from there. Not giving up.
Reply: refrigerant gases are odorless
I may be missing something but refigerant, existing in either a gas or liquid state, remains inside an enclosed HVACR system of pipes, valves, controls, and a receiver and a compressor. It doesn't come indoors and outdoors, it doesn't leak out of a system in normal operation, and it is odorless and colorless.
I agree Daniel. My head is about to explode from all the information that is hitting me left, right & center.
Yesterday, we had a video camera inspection done to see all the ductwork in the house. It was recommended we do this because concrete slab homes like ours tend to get water in their in-ground ductwork. As a result, odors are caused. The inspection proved there is no water. Thank goodness. However, we still need to find the source of the evergreen odor. When the AC was put on, the technician was very concerned because the coil was staying warm. Most likely the refrigerant (freon) is leaking out somewhere. The HVAC service that installed the furnace & AC back in 2009 is coming in a few hours to check the charge on the AC. If the charge test is not good, the next step will be the sniffer and/or dye test to locate the leak.
Reply: Notorious problems with ducts in slabs
Freon (or other HVAC refrigerants) does not smell. It is odorless.
Re-charging a refrigerant gas is only part of a proper repair. The leak needs to be found and fixed.
Ducts in slabs are a notorious source of contaminants: moisture, leaks, rodents, mold; Perhaps someone sprayed a sanitizer or odorant in the ductwork.
See SLAB DUCTWORK for an explanation of the problems commonly found with HVAC air ducts placed in or below concrete floor slabs. For example, anything sprayed into or even leaking into the in-slab ducts could be a source of odors later detected in the building.
The HVAC company that installed the furnace & AC in this house back in 2009, came out. We had to wait for at least 60 degree weather for them to check the charge on the AC and do the sniffer test. As I expected, the refrigerant was bone dry. Also, the leak is in the coil. That being the case, the entire coil is being replaced. We are still under warranty thank goodness for parts & labor on the furnace & AC.
Reply: look for cleaners, deodorants, and compressor oil leaks
The relationship between odor and no refrigerant is a tenuous one at best. Perhaps that the system was not cooling and not dehumidifying is a factor in odor development (e.g. mold in a damp area) or odor transmission. In short, you still need to track down the "evergreen" odor source.
Have you determined if a deodorant or sanitizer or cleaner was sprayed or used in the HVAC system or in a building area where such odorants might be picked up by the HVAC air handling system?
Sheila it occurs to me that your installers, in finding the refrigerant leak, should also look for a compressor oil spill or leak anywhere in the system. While refrigerant gases are inert, odorless, colourless, lubricants within the system might have a smell - though not one I'd describe as "evergreen". It remains that an evergreen smell seems more likely to trace to a cleaner or deodorant.
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.
Question: oil fired furnace pulls smoke & fumes into house during burner shut-down
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:
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Frequently Asked Questions (FAQs)
Question: new plastic odor from vents
July 9, 2014) Kay said:
Possibly a burning electrical motor, wire, wire insulation, or an odor being picked up at an air return and transported through the building.
Question: chemical odors from central air system
(Aug 3, 2014) bob said:
(Sept 6, 2014) josephine said:
Question: stale odors from ductwork
(Nov 12, 2014) fruce bagheri said:
Check for leaks into the duct system or dirty ducts that need cleaning.
Question: Foul urine odor from ductwork
There is a oul urine odor coming from our ductwork
Look for animal urine near an air return or look for mice or other rodent invasion of the ductwork.
Watch out: for bacterial or viral hazards from mice or other animals in the HVAC system
12/28/2014 Anonymous said
I have an intermittent stale dry ice odor coming from ceiling vents during heat cycle only, not ac. Outside temps have been between 40s & 60s. Not sure if defrost cycle has ever kicked in, or aux heat. Unit is 8 mo old. Any thoughts anyone?
I'm not sure what dry ice odors means - dry ice is frozen carbon dioxide or CO2 which is odorless. I'd give the HVAC service company a call to ask for assistance.
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