Collapsing building © Daniel Friedman Common sources of chemical smells or odors in or near buildings

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Chemical odors in or near residential buildings: this article describes clues, focused on common sources of building chemical smells or chemical-like odors, that any home owner, home inspector, or other investigator can follow in seeking to pinpoint the source of an annoying or obnoxious odor in buildings.

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Checklist for Diagnosing the Cause of Chemical Smells in buildings

Odor absorber on display rack (C) InspectApediaOften people's perception of odors varies with time and exposure or with a number of other site factors that make it hard to track down just where a smell is coming from.

But if we think carefully about when, and under what conditions we notice odors, often that information is instrumental in tracking down an odor to its source and thus in helping us decide if an odor refers to a potentially dangerous or unhealthy condition.

Photo at left: Air Sponge™ is an odor absorber product for sale at a building supply store and described by the manufacturer as effective in areas up to 300 sq. ft.

In our opinion no odor absorbing product can handle a troublesome building odor problem in a building if the odor source is not found and removed. Using dust removal as an analogy, imagine waving a vacuum cleaner wand in the air in your kitchen in hopes that the dust bunnies under the living room couch will somehow be removed.

A principal ingredient in many such odor-absorbing products is sodium bicarbonate - (baking soda) - a hygroscopic material that readily absorbs moisture from the air and that may absorb some odor molecules as well [22]. But because an odor reservoir, like a mold or dust reservoir in a building, can produce effectively a continuous source of smell, the most effective way to remove a building odor is to find and correct its source.

This building chemical odor source list is in simple alphabetic order, not in order of probable cause, importance, or health risk, all of which can vary widely.

  • Acetone or similar chemical smells in well water - see ACETONE in WELL WATER below in this article
  • Building Chemical Odors & Common Indoor Air Pollutants - some indoor air pollutants may include an odor described as "chemical" -
  • Building Chemical Odors & Animals: on occasion we have received reports of a "chemical odor" complaint in a building that is ultimately traced to an animal, usually a dead one trapped in a wall, ceiling, or crawl space. See ANIMAL or URINE ODOR SOURCE DETECTION.
    Also possibly helpful will
  • Building Chemical Odors & Appliances: does the odor appear only when certain appliances are running: cook stove, air conditioner, heater, aquarium pump, fans, clothes dryers, clothes washers, dishwashers, or electrical devices such as TV's? Some appliances may be overheating, heating plastic components, or may be experiencing an electrical problem that is actually burning electrical components or plastic wire coverings.
  • Building Chemical Odors & Building Structure: does the odor relate to presence of a nearby air movement pathway such as a building stairwell, elevator shaft, or heating and cooling duct system? For example, we have traced odors in an upper floor of an office building to smells transported through a nearby elevator shaft, by a stairwell, and across an extraordinarily long suspended ceiling cavity from a distant beauty parlor.
  • Building Chemical Odors & Carpeting or carpet padding: some building chemical odor complaints are traced to (usually new) carpeting, particularly wall-to-wall carpet products, and to carpet padding, particularly foam or rubber carpet padding and underlayment products.
  • Building Chemical Odors & Chemicals Used in or around the building: what chemicals have been applied or used in or around the building that may produce constant or episodic (depending on temperature, humidity, sunlight, wind direction, operation of HVAC equipment etc) odors in or near the building. Examples of some odor sources that at least some readers describe as "chemical" in nature form a very long list, of which some common items mentioned include:
    • Building activities: while our checklists focus principally on residential or office space odor complaints, chemical odors may be transported through a building from more distant activities such as the beauty parlor we mentioned above.
    • Cleaners & cleaning chemicals or solvents
    • Gas leaks, LP or natural gas odors -
    • Electrical system failures: burning wire insulation or over-heated electrical components, e.g. backup electric heat failure in a heat pump system or aluminum electrical wire overheating -
    • Heating oil fuel spills
    • Medications, drugs, spilled liquids
    • Mold odors - MVOCs may be present even if mold is not visible - a musty "chemical" smell
    • Oxidized plastics and other materials from improperly-used ozone generators in buildings, vehicles, other enclosed spaces
    • Ozone - from incorrectly-used ozone generators in buildings b
    • Paints recently applied inside or outside the building
      and also
    • Pesticides applied near or inside the structure
    • Scented candles and other building odorants or "deodorants" generally produce what I describe as a sweet or perfumed smell but some occupants may use the term "chemical" odor for these as well.
    • Sewer gas leaks
  • Building Chemical Odors & Chimneys: chimney creosote, particularly from wood-burning appliances can be a source of "chemical" odors in buildings.

    Watch out: chimney creosote build-up is a serious building fire hazard.
  • Building Chemical Odors & Drywall:
    See CHINESE DRYWALL HAZARDS outgassing can produce a sulfurous or chemical smell
  • Building Chemical Odors & Fans: while exhaust fans are often used to move odors out of a building, a little thinking and investigating may be in order: does the exhaust fan or whole house fan or attic roof vent fan cause odors, dust, or even mold to move upwards through the building? (Be careful that your whole house fan or other exhaust fans do not overpower and cause improper operation of your radon mitigation system if you have one installed).

  • Building Chemical Odor history: when was the odor first noticed? What date? For how long has it been observed? Who first observed it? Does the first occurrence of a smell relate to an event, change, or modification in the building? If so, what exactly?
  • Building Chemical Odor location: does the odor appear throughout a building or only on certain floors, in certain rooms, or at certain walls?
    • What is different about the room where an odor appears:
      • What side of the building is the room on? What conditions are different there such as sun exposure, wind exposure, nearby trees, prevalent wind direction, outdoor possible odor sources?
      • What side of the room, what wall, has the strongest odor: is it an exterior or interior wall?
      • What materials are unique to the odor-source room, such as carpets, carpet padding, drapes, window shades, kind and type and age of windows, screens, heat, air conditioning, pet occupancy, people occupancy, laundry storage, proximity to baths, kitchens, laundry, openings between floors?
    • What is different about the floor or level in a building where odors occur? Proximity to basements, attics, leaks, rodents, pests, animals, heating equipment, pesticide treatments

      On request we can describe a procedure that assists in pinpointing odor sources to a particular surface or piece of furniture or carpeting, using aluminum foil, paper towels, and simple masking tape.
    • Further odor source tracking suggestions are at
      BUILDING ODOR SOURCE Q&A in this article (below)

      See ODOR DIAGNOSIS CHECKLIST, PROCEDURE that provides a checklist of places to look and things to do to track down the source of an odor or smell in building air, water, mechanical systems, heating, cooling, or other locations.

      ODORS GASES SMELLS, DIAGNOSIS & CURE offers a collection of articles that describe steps to track down an odor to its source and to correct the problem

      SMELL PATCH TEST to Track Down Odors helps track down odors by testing the surfaces of possible odor sources such as carpets, walls, furniture
  • Building Chemical Odors & Mold: Some building occupants describe mold smells as chemical. Separately a building mold contamination cleanup project can lead to horrible chemical smells if inappropriate use of ozone generators is involved (oxidized building materials) or if bleach or other chemicals are misapplied.

    Separately again, in a series of articles on flooded vehicle detection and curing car, boat, RV or other vehicle mold smells we discuss odors that appear in cars, including antifreeze leaks.
  • Building Chemical Odors & Neighbors: does the odor correlate with activities by building occupants or building neighbors? What about trash burning, level of septic system usage, use of woodstoves, coal stoves, home improvements, building projects.
  • Building Chemical Odors & Occupants: does the odor occur when the building is occupied by large number of people, visitors, or specific individuals who may have brought something new into the building?
  • Building Chemical Odors & Plastic or Vinyl building materials: in addition to paints and electrical products involving plastics, quite a few building smell complaints described as a chemical-plastic odor have been traced to vinyl siding, vinyl windows, plastic window screens, and even plastic interior or exterior trim, even plastic window shades. See VINYL SIDING or WINDOW PLASTIC ODORS
  • Building Chemical Odor Perceivers: who notices the smells? Is the odor perceived only by certain occupants? Is the odor more noticeable to building occupants or to occasional visitors.

    People's sensitivity to many odors tends to diminish over longer exposure times as the odor-sensing neurons and brain response become desensitized.

    Such individuals may notice an odor only upon entry to a building and not after being indoors for a time; people can also become desensitized to an odor such that even after leaving and returning to the building they do not notice the odor as much as is noticed by visitors. This seems especially true with animal and pet odors for people who live with pets.
  • Building Chemical Odors & Plastic smells:
  • Building Chemical Odor Strength: is the odor perceived as strong or mild?
  • Building Chemical Odors & Time of Occurrence: does the odor appear all of the time or only at certain times. For odors that come and go, does the time of the odor correlate with:
    • Time of day, sunlight, operation of heating or cooling equipment
    • Time of year, season, foliage, outdoor or indoor activities
    • Heating or cooling season: does the odor appear when the heating system comes on? Check immediately to assure that there are no carbon monoxide hazards or flue gas hazards. While carbon monoxide itself (CO) is odorless and colorless, more often CO is mixed with the exhaust gases of heating appliances burning heating oil, gas, or other fuels that produce other fuel-related odors.
      See CARBON MONOXIDE - CO [which is odorless but may be mixed with heating system fuel gases that can be smelled]
    • Cooking activities may be an odor source

  • Building Chemical Odors & local Temperature or Sun Exposure: does the odor appear or disappear in relation to changes in building temperature?
    • Sunlight striking plastic window screens may make a distinctive odor only on the sunlit side of the building
    • Plumbing system drains or vent systems may release odors when a private septic system is under heavy use or in certain weather conditions -
  • Building Chemical Odors & water: while there are a number of common contaminants that produce odors in the building water supply, we don't usually ascribe a general building smell or odor to its water or water source since normally water is not running constantly indoors.

    But buildings with pools, fountains, or where there are odor complaints that track to the operation of showers or sinks,
  • Building Chemical Odors & weather conditions: does the odor correlate with weather conditions such as humidity, temperature, rain, snow, wind?

Keep a Building Chemical Odor or Chemical Smell Diagnostic Log: Use any of the files listed below to record various data that can help figure out the source of a mystery odor or smell - we recommend the first Odor Checklist Form listed below as it is the most detailed version.

  • ODOR EVENT LOG & CHECKLIST FORM printer-friendly PDF file to record odor observations such as time of day, weather, temperature, sunlight, & possible sources as an aid in finding the actual source of odors & smells in or around buildings

  • ODOR LOG EXCEL Spreadsheet to record your observations for further analysis for those who prefer to work with spreadsheets to enter odor observation data

  • ODOR LOG abbreviated form "short list" printer-friendly PDF file lists observations that can help track down an odor source.

Reader Question: Acetone Smells in Well Water

(Oct 17, 2014) KAREN VAN ESSA said:

For the first time in 10 years I can smell acetone intermittently in my cold water, which comes from a drilled well 130 feet deep. I have had the water tested for a broad range of chemicals at least twice before: levels were below all guidelines, except for sulphur and hardness, but the levels are tolerable and I have no water softener.

There has been no construction in my rural neighbourhood, the nearest house is 500 feet away, and the only industrial site is a car wreckers/body shop about 1/2 a mile away whose owner is semi-retired.The land has not been farmed for at least 25 years. What could be the source of this volatile? Could it be natural? (this is a mainly wooded area with small streams and ponds)



Acetone would not be associated with a septic system failure or odor problem -
[ this question was originally posted at SEPTIC SYSTEM ODOR CURES]

I would begin with a lab test to identify what's actually in the water supply. Knowing that accurately will help pinpoint possible sources.

Acetone in well water research citations

  • Rezaee, Mohammad, Yaghoub Assadi, Mohammad-Reza Milani Hosseini, Elham Aghaee, Fardin Ahmadi, and Sana Berijani. "Determination of organic compounds in water using dispersive liquid–liquid microextraction." Journal of Chromatography A 1116, no. 1 (2006): 1-9.
  • Atwood, Jerry L., Leonard J. Barbour, Timothy J. Ness, Colin L. Raston, and Paul L. Raston. "A well-resolved ice-like (H2O) 8 cluster in an organic supramolecular complex." Journal of the American Chemical Society 123, no. 29 (2001): 7192-7193.
  • Kozani, Reyhaneh Rahnama, Yaghoub Assadi, Farzaneh Shemirani, Mohammad-Reza Milani Hosseini, and Mohammad Reza Jamali. "Part-per-trillion determination of chlorobenzenes in water using dispersive liquid–liquid microextraction combined gas chromatography–electron capture detection." Talanta 72, no. 2 (2007): 387-393.

the latter also discuss chlorobenzenes

Reader Question: Chemical odors, air fresheners, ozone, secondary air pollutant hazards: I can't pin down the source of a chemical odor in my house. Any suggestions?

I was just looking at your web site hoping to find some answers for my problem and didn't really see what I was looking for. I'm hoping you can make a suggestion or point me in the right direction.

I've been chasing an odor around my house for almost a year now and can't seem to pin it down. What it is or where it is coming from.

I've had a plumber come to my house, HVAC person, local gas company, city sewer people, and talked to a "mold" guy although I didn't have him come to my house. I bought my house new eight years ago and it's only 1100 sq. ft. and I don't find any evidence of water damage that would precipitate a mold situation.

The smell has a chemical nature to it that I think is now starting to cause some health concerns for me. Since I've pretty much weeded out all of the obvious things about all that is left next door neighbor cooking drugs of some type. I've filed several reports with the local police department and done several other things as well. Law enforcement may or may not be investigating the situation. They don't really say anything one way or the other.

It seems to me that I need some way to determine exactly what the odor in my house is; but I don't know how to go about it. Everyone that I've spoken to can check for things like sewer gas or mold spores but trying to ferret out the ingredients that might be used for cooking drugs is a whole different ball game. Not really that easy as far as I can tell. I've seen some electronic equipment on-line that is for sampling for residue inside houses where drugs have been cooked but that's like a first-hand situation. My situation is more like a second-hand smoke deal.

Please let me know if you have any suggestions. I'm pretty desperate at this point. - R.E.

I have an office attached to my home which is outgassing from an unknown source. Possible culprits are formaldehyde from an air freshener concentrate spill or perhaps hard foam ceiling insulation. Any suggestions on how to identify the nature of the gas and what to do about it - Lawrence Jackson 3/28/12

Reply: Visual inspection of materials and building condition and a series of smell patch tests might help; secondary air pollutants from air fresheners & ozone generators


Since tests to capture a gas and then identify it can be costly to arrange, it makes sense first to trace the odor to its source - often what you see there will be diagnostic. But I and experts agree that an indoor "air freshener" (such as the plug-in type) can in fact be a source of secondary pollutants, and we agree that some indoor air fresheners include a small amount of formaldehyde, typically 0.1%, to keep the air freshener from growing organisms.[8] Also
see Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.

Too often an air freshener is not really removing anything from the air to make it more "fresh" - rather it is adding chemicals that cover up the original odor (leaving it in place) and/or chemicals that deaden your sense of smell so you just don't notice the original odor. These concerns for secondary air pollutants can be even more severe if people try using ozone generators in the same location. [6][7][8][9][10]

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem and in this particular case s/he might quickly spot something known to be a common source of problem odors but that had remained unfamiliar to you and some of the others who've looked. With no specific information about your building, I can only suggest a general approach to tracking down the odor problem.

That said, here are some things to consider:

Separate probable emergencies from other odor problems

Of course some odors are widely recognized by many people and some of these (fuel gas odors, methane, sewer gases, even flue gases) can be indicators of very dangerous conditions that need prompt action.

Sophisticated tests to identify gases and chemicals in buildings

There are gas testing methods that can identify the chemical constituents of gases (or in other words odors) found in buildings and elsewhere using a combination of a vacuum canister to collect air samples and mass spectrometry and similar instruments. Industrial hygienists are equipped and familiar with these procedures, but I'd be careful: most of the hygienists in my association (AIHA) are industrial experts and only a smaller number are familiar with residential buildings and with the building science needed to understand and diagnose and cure odors in residential homes.

But for other smells in general I am reluctant to order gas and chemical tests to "identify" an odor for several reasons

An odor or smell may be the mix of a number of chemicals produced by a particular building product or condition. Identifying the specific chemical constituents of the gas often fails to point to the actual source in a building.

I have found inconsistent results from test labs and on occasion even large expensive labs have returned poorly-developed and unreliable results. It seemed to depend on luck of the draw about which technician and supervisor actually handled the work.

A chemical signature that identifies odor components might suggest a direction of investigation but equally frequently in my experience tests of air or gases in buildings are not sufficiently diagnostic. The results may confirm an odor while taking very limited or no steps at all towards identifying the odor source and no steps whatsoever in guiding the building owner into a plan of action.

These tests tend to be specific in target and expensive in use.

Suggestions for tracking down smells in residential buildings

I have had best results in tracking down and eliminating odor problems in buildings by using various measures to pinpoint the actual physical odor source. When the source is recognized we usually will know quickly just what the material is or just why the odor is occurring.

There are other helpful variables to consider that also help track down an odor source such as the correlation of odors to weather, wind, moisture, temperature, sunlight, sun exposure to different building areas, time of day, operation of various equipment etc.

For sources more far afield it's sometimes important to make sure that the odor is originating inside the building not elsewhere.

For odor complaints that are not observed by everyone in the building, because individual sensitivity to odors and chemicals can vary widely I don't assume that the "non-smellers" are correct (that there is no problem) but I have encountered cases in which a medical or even neurological condition was involved.

Help in tracking down an odor source based on building conditions:
See ODOR DIAGNOSIS CHECKLIST, PROCEDURE that provides a checklist of places to look and things to do to track down the source of an odor or smell in building air, water, mechanical systems, heating, cooling, or other locations.

Help in tracking down an odor source based on actual strength of the smell:

Above and in a series of articles found beginning at
ODORS GASES SMELLS, DIAGNOSIS & CURE we provider a collection of articles that describe steps to track down an odor to its source and to correct the problem, and there we include a suggested
SMELL PATCH TEST to Track Down Odors
that might help track down odors.

Use a combination of people with a good sense of smell and the smell test to see if you can identify where, when, and under what conditions the problem odors are strongest.


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CHEMICAL ODOR SOURCES at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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