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Smell patch test procedure: how to use paper towels, aluminum foil, and tape to perform a simple but effective odor source test of building surfaces and materials.

This article describes a simple procedure using paper towels and aluminum foil wrap to track down odors in buildings, such as but not limited to tracking down mold smells, sewer smells, plastic smells, chemical odors, animal odors, and even new smells that occur after excessive indoor use of ozone in buildings to try to "kill" mold or remove other indoor odors (skunks or smoke). Our page top photo shows the last step in the smell-source test procedure, though we recommend that this step be conducted outdoors in fresh air.

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How can I Track an Indoor Odor to its Source?

The procedure we describe here is easy, inexpensive, and fast - you'll need a day or so, plus some common household materials to track down an indoor smell to the surface or material that is its most likely source.

Depending on what caused the material to smell in the first place, disposal may be the only option. In other cases, amateur or professional cleaning or use of sealant paints may be effective. If you've already tried using an ozone generator to kill an indoor odor, you may have used the equipment improperly. Ozone or O₃ is a highly reactive oxygen molecule that can cause oxidation of materials that it touches. This oxidation, especially of some rubbers and plastics, can leave a horrible smell in the treated building.

Using Ozone to Get Rid of Skunk or Mold Smells?

This quote from a reader's email pretty well sums up what happens if you overdo it when using an ozone generator indoors to try to "kill off" odors:

It's a long story, but I used a high powered ozone generator in our house, to get rid of skunk smell. Now I can't get rid of the left over nitric oxide, or whatever odor or gases, that linger in our house. I have been leaving the windows open every day, with running the heat on high (85 degrees) at night, to try to force off-gas the odors/gases.

We have investigated a number of cases of misapplication of ozone generating machines both to "kill mold" (no good, you're leaving toxic or allergenic particles, and you haven't corrected the reason for mold growth in the first place). We have also investigated several cases of excessive ozone-use to try to remove odors from buildings, including fire or fireplace smells, mold smells, pet or animal smells, skunk odors, smoking odors, etc.

Using an Ozone Generator Has Left a Smell in our Home - How do I Get Rid of It?

If you have aired out the building and days or more have passed and you still smell a "new" chemical or plastic or other odor that was not there before you tried using your ozone generator, you'll need to determine just what materials were oxidized by the high levels of ozone in the building.

It's been our experience that once you identify and dispose of the new-smelly material you'll probably be fine. Here are some examples of material we've found giving off horrible smells after misuse of an ozone generator. (Misuse means using the ozone generator to try to kill mold, or running an ozone generator too long at too high a setting in too small a space - overdoing it).

• Carpets, especially synthetic carpets
• Carpet padding
• Foam cushions
• Other plastic furnishings or furniture covers
• Rubber pads, padding

Try the Smell Capture Patch Test to Pin Down a Specific Indoor Odor Source

Our friend Jeff May suggested this procedure for pinning down a specific odor test in buildings - it has worked remarkably well for us where ozone had caused an indoor smell that could not be tracked down. Our photo (left) shows the supplies you need as well as a test set up on the surface of wall to wall carpeting. We have added to, elaborated, and provided details of just how this smell patch test works - below. Purchase these indoor odor track-down supplies if you don't already have them A roll of new clean odor-free paper towels (not something that has a perfume in it) A roll of new clean foil wrap A roll of blue easy-to-remove masking tape or painter's tape Close up the building - windows, and doors

• Prepare and apply odor collecting test patches on the surface of each suspected material such as carpeting, carpet padding wall surfaces, trim surfaces, furniture surfaces
  • Fold a paper towel into quarters and place or hold it on the surface to be tested.
  • Tear off a sheet of foil wrap that is several inches larger than the folded paper towel
  • Place the folded paper towel on the surface to be tested (Photo above left shows this smell locator test set up on wall to wall carpeting - we would also recommend a separate test of the carpet padding below the carpeting)
  • Place the foil wrap over the paper towel
  • Tape the foil wrap in place using the blue painter's tape (Photo above right)

• Prepare and apply additional odor-collecting test patches on all other building surfaces to be tested as an odor source. Typically these include:

• Rug or wall to wall carpet surface in most-suspect area
• Rug or carpet under-padding
• Painted wall surfaces (Photo at left)
• Plastic or vinyl windows, trim, blinds, curtains
• Surfaces of furniture suspected as an odor source, especially couches and chairs stuffed with foam padding if odor problems followed use of an ozone generation machine
• Prepare additional control test patches (optional) - we apply multiple samples to the same surface as a test control described below
• Wait 24 hours or longer - you are allowing odors and gases under the paper towel to impregnate and be absorbed into the paper towel. Do not disturb the foil covering the paper towel during this time. The foil covering assures that what's being absorbed into the paper towel is emanating just from the surface being tested. The aluminum foil will also be used to quickly wrap and trap gases in the odor-filled paper towel at the end of the test period.
• Station your test subject person outdoors in fresh air out of the wind - select someone with a good sense of smell, or best, the person who has already complained of a specific odor in the building

• Test each smell patch as follows:
  • Lift a corner of the masking taped foil-covered paper towel test patch (Photo at above left, peeling-off is in process. Don't stop to take a photo like this or you may lose some of the odor absorbed in the paper towel.)
  • Quickly fold the paper towel patch inside of the foil that was used to cover it - do this quickly so you don't contaminate the patch of paper towel with other indoor air or gases (Photo at above right shows that we have sealed the paper towel completely inside of the foil covering)
  • Take the smell test package outside into fresh air in a non-windy location: Quickly carry the paper towel patch, now folded in foil, outside and present it to your test person
  • Conduct the smell test: The test person opens the foil wrap and sticks his/her nose into the paper towel and sniffs, reporting when s/he smells the offending odor that was previously the complaint in the building.

Test your control smell patches as follows:

• Present smell test and smell test control patches to the smell-test person, without telling him/her the surface from which it was taken nor which sample is which - odor or control.
• Tear open a corner of the foil covering the smell-absorbing paper towel - just large enough to get the test person's nose inside of the foil. (Photo, above left)
• The smell test person sniffs the paper towel and reports their observations. (Photo, above right)

If a smell test is definitive, the test person will usually report very accurately which patches are from a given smell or surface area.

We have had very good results with this procedure when used to narrow down odor sources in an ozone-treated building, and we had up to 95% repeatability when we used additional smell test patches.

Questions & Answers regarding this article

Questions & answers about using simple methods to track down the source of a building odor or smell.

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SMELL PATCH TEST to Track Down Odors

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.
• Environmental Health & Investigation Bibliography - our technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
• Adkins and Adkins Dictionary of Roman Religion discusses Robigus, the Roman god of crop protection and the legendary progenitor of wheat rust fungus.
• Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
• "A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
• US EPA - Mold Remediation in Schools and Commercial Building [ copy on file as /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
• US EPA - Una Breva Guia a Moho - Hongo [on file as /sickhouse/EPA_Moho_Guia_sp.pdf - - en Espanol

Mold Contamination Testing, Cleanup, Prevention: references & products

• The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
• Aerobiology, Building Science, Microscopy, & Laboratory References, an extensive technical bibliography
• Allergens: what they look like in buildings
• Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
• Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon)
• Atlas of Mold Related Illness: Index of Symptoms and health, physical, neurological, psychological, and other complaint which people suspect may be mold or building-related.
• Atlas of Indoor Mold, Online Clinical Mold Atlas, Toxins, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
• Black Mold that is Harmless Photos of recognizable, usually harmless black mold on wood, bluestain, ceratocystis, ophistoma
• Building Floods: quick steps after a building flood or plumbing leak can prevent costly mold contamination
• Classes of Mold: what types of cosmetic, allergenic, or toxic mold are a problem? Can mold be cleaned-up successfully?
• Clinical Mold References - Detailed bibliography of mold reference texts
• "A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
• "Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
• "Disease Prevention in Home Vegetable Gardens," Patricia Donald, Department of Plant Microbiology and Pathology, Lewis Jett
  Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
• "Management of Powdery Mildew, Leveillula taurica, in Greenhouse Peppers," Ministry of Agriculture and Lands, British Columbia - Original source: www.agf.gov.bc.ca/cropprot/peppermildew.htm
• Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
• Fiberglass: Mold in Fiberglass Insulation© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation - DJF
• Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
• Fungi, Identifying Filamentous, A Clinical Laboratory Handbook, Guy St-Germain, Richard Summerbell, Star Publishing, 1996, ISBN 0-89863-177-7 (English) (buy at Amazon)
• Looking for Mold Procedure: what mold is often found where in buildings - simple technical presentation
• Meruliporia: the house eating fungus or "poria"
• Mold Action Guide: Step-by-Step Instructions, What to do about mold, mildew, and other indoor allergens
• MOLD APPEARANCE - WHAT MOLD LOOKS LIKE Photos of what mold looks like in buildings
• MOLD APPEARANCE - STUFF THAT IS NOT MOLD Photos of NOT-mold material that is sometimes mistaken for mold
• MOLD ATLAS & PARTICLES INDEX, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
• MOLD BY MICROSCOPE Mold under the microscope - photo identification of the most common indoor molds found in buildings
• Mold FAQs Answers to Most Questions about Indoor Mold, Mold Related Illness, Mold Cleanup, Mold Prevention
• US EPA: Mold Remediation in Schools and Commercial Building [ copy on file as /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
• Mold spores in the Home - a Photo ID Library for detection and identification of mold allergens
• Mold Test Kits - How to Collect and Send Your Own Mold Sample to our mold testing lab or to any mold lab you wish
• Most Common Indoor Molds Found in Buildings, A Table of
• Mycology, Fundamentals of Diagnostic, Fran Fisher, Norma B. Cook, W.B. Saunders Co. 1998, ISBN 0-7216-5006-6 (buy this book at Amazon)
• Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
• Rot concerns in buildings-some building mold such as Meruliporia incrassata "Poria" risks serious rot and hidden structural damage
• US EPA: Una Breva Guia a Moho - Hongo [on file as /sickhouse/EPA_Moho_Guia_sp.pdf - - en Espanol

OTHER IAQ ISSUES: How To Find and Address Other Indoor Air or Indoor Environment Contaminants Besides Mold

Mold or allergens may not be the only or even the main indoor environmental contaminant. Don't let media attention to mold cause so much enviro-scare fear that other, possibly more urgent hazards go un-addressed.

• Fiberglass building insulation and HVAC duct work insulation hazards
• Sewage and Septic backup contamination in buildings: inspection, testing, remediation, & references to expert sources
• Other environmental risks: Asbestos, carbon monoxide, electromagnetic fields, environmental illness, fiberglass, MCS - multiple chemical sensitivity, toxic gases, etc
• Indoor Gas Sampling Plan for Residential Buildings lists a number of toxic indoor gases which we test for, depending on the building complaint and building conditions
• Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
• Pet control - if you can't say goodbye to your bird, cat, dog, guinea pig, hamster, tropical fish, then limit the areas they occupy and limit the airflow from that area to sleeping or other areas of the building, use allergenic bedding, eliminate wall-to-wall carpeting, improve housecleaning including use of a HEPA-rated vacuum cleaner. For more details see our article Dog, Cat, and Other Animal Dander - Information for Asthmatics and Indoor Air Quality
• Rodents, Mice, Squirrel Control - I find high levels of mouse and rodent dander, fecal dust, and urine-contaminated dust in some buildings, and high levels of these materials in building insulation in those locations. If you have a mouse problem, particularly if mice and their waste (fecals or urine) are contaminating the building HVAC or building insulation, may need both steps to clean up or remove infected materials and steps to stop an ongoing rodent problem. If squirrels are a problem, the cleanup needs to include closing off entry openings into the building. Get some help from a licensed pest control expert.
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