Do you have a curious spot in your home that you suspect may be mold?  How would you know?  How would you know if it’s toxic mold?

This article will explain how homeowners and renters alike are able to conduct their own inexpensive DIY mold investigation using sticky tape sampling.  The purpose of tape sampling is to find the sources of mold growth (whether visible or hidden) that should be cleaned up in your home. Once you identify the sources, you can better determine what needs to be done to clean them up safely and effectively.

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Tape testing allows you to save money by playing an active role in your own mold inspection.   The process is super simple:

  1. You will touch a 3″ piece of clear tape to the suspect surface
  2. Mail your samples off to be looked at under a microscope
  3. Receive an environmental mold report with information on what type of mold it is, how dangerous it is, and what action steps you should take next.


Why DIY Mold Tape Testing Should Precede a Mold Inspection

According to May Dooley, tape testing should be your first course of action, even if you plan to hire a professional mold inspector.

“Why? Because the local mold inspectors frequently miss sources of mold. The reason for this is simple: They don’t work with an on-site microscope. If you don’t fill in the gaps, it’s probable that no one else will. If you want a full mold inspection done at your home, you are going to have to step up to the plate. Period.

You and I, working together, can do a more in-depth job than most mold professionals. It will cost you a lot less, too. Why don’t mold professionals bring a microscope to the job? You’ll have to ask them that question. I’ve never been able to figure it out.

If they say that they aren’t “certified microbiological labs,” neither am I. That fact doesn’t stop me from using the best tool I have for a mold inspection. If mold is found, I show the homeowner on my computer monitor what it looks like. If independent third party confirmation is needed, a fresh sample is mailed off to a microbiological laboratory. You get the best of both worlds, the on-site workhorse microscope for immediate answers and the option for laboratory confirmation where needed.

This is not to detract from the talents and experience that many mold inspectors bring to the job…you just want a thorough job to be done. I understand that. You don’t want a satisfactory air sample report in the kitchen, only to have the inspector miss the active mold contamination inside the kitchen sink cabinet because the mold happens to be invisible to the naked eye and didn’t show up in the air sample. You get my drift?

No matter how good a local mold inspector is, the chances are high that he or she will miss mold growth if they don’t bring a microscope along to your home…either that or a crystal ball. Having a microscope isn’t a 100% guarantee of finding all sources of mold growth, but there’s a much better chance of identifying all sources than without a microscope.”


Supplies Needed

  • Transparent tape appropriate for microscope slides
    • Important: Not all types of tape will show up on a stained microscope slide, so ONLY one of the following brands/styles of tape should be used: 3/4″ Wexford brand transparent tape (also available at some Walgreens) or Walmart’s store brand transparent tape (red and black packaging).  Do not use packing, “magic,” invisible, or satin tape.
  • Sharp scissors and a ruler
  • One pair of nitrile gloves (size medium) for collecting samples
  • One N95 face mask for collecting samples
  • Numbered labels for your tape samples, and a key for reference
  • Quart or gallon size plastic zip bag
  • 1-page Client Information Sheet for providing to the lab
  • A pre-addressed envelope for mailing your samples to the lab

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How to Take Your Own Mold Tape Samples:

Detailed instructions download coming soon.


Who Should Take Their Own Samples?

Taking your own samples is a great starting place because it is relatively inexpensive and you can do it yourself.  It is also a great way to get peace of mind in knowing if an offending stain is toxic mold!

It is important to note, however, that tape testing is just one of more than a dozen ways to test your home for mold and that taking your own mold samples is likely insufficient evidence for legal cases.

If you suspect a mold problem,  I just wrote a primer on mold testing options – I’d suggest you start there.

Overall, DIY tape testing may make sense if:

  • You have small amounts of visible mold, and you want to know if it is dangerous
  • You smell the “musty” smell of mold or mildew, but need help locating it
  • You recently acquired antique or second-hand furniture, and you want to be sure it is mold-free
  • You suspect that someone in your home is experiencing asthma or allergies related to mold

Mold tape testing is NOT advised if:

  • You have large amounts of visible mold.  Please keep in mind that mold can be extremely dangerous to human health!  If you think you may have a significant mold problem, please work with a certified mold professional.
  • The person who will be taking tape samples has asthma, allergies, or mold detox issues; If you currently have respiratory illnesses or are immuno-compromised, I would not suggest doing any of your own mold testing, tape testing included.

Important Disclaimer:  These samples are studied in-house, for informational purposes only, not for legal purposes. If legal action is contemplated, you should arrange for an inspection by a mold inspector, with samples submitted to a certified microbiological laboratory. Even though I will provide you with photographs of what I see under the microscope, I have not taken your samples and doubt that the photographs would hold up in court.


Additional Mold Testing Tips

I recommend working with May Dooley of EnviroHealth Consulting One of the best pieces of advice May gave me is to trust your nose.  Follow that “musty” smell, including smelling the wall outlets, to determine if mold is present in the wall cavity behind there.

  • “If you are concerned about a leak, then test the leak area, bearing in mind that most of the mold could be hidden and there may be no accessible evidence for tape-testing. Use tape wrapped around a blunt kitchen knife or putty knife to try to slide into cracks and crevices.
  • If you are concerned about a shower leak, try to slide a blunt kitchen knife under the base molding in the room sharing a wall with the shower (or toilet or sink cabinet);
  • If there is a shower access, open that and look inside for black mold on the back of drywall.
  • If you are concerned about water in a wall cavity, try the kitchen knife approach under the base molding. Do this under finished basement walls if applicable.
  • If there is visible mold on a wall, send a tape sample from the area of discoloration. Otherwise, testing walls usually results in a negative finding, because paint contains a mildewcide to ward off mold growth.
  • Test for mold in a sink cabinet by touching the tape to multiple surfaces around the plumbing, including the crack where the back wall meets the base of the cabinet and if you can get your finger through a plumbing access hole.
  • Walk around the perimeter of the house. If there is any place where dripping or standing water is present – or where a gutter downspout terminates next to the foundation, test inside under base molding at that area.
    (Wholesome Tip: When testing outdoors or near the foundation, avoid getting too much dust or debris on a tape. It could be hard to pick out mold spores among the rest of the debris.)
  • Black mold on AC vent covers, bathroom ceilings, and refrigerator gaskets is usually Cladosporium, an allergenic mold that likes areas of condensation. This mold also grows on AC coils, should you be able to access the coils for sampling.
  • Reach deep inside a floor vent or two and touch a tape to sides and tops (avoiding where debris would mostly gather).
  • If you are concerned about elevated relative humidity, then test areas where mold might grow, such as unfinished, rough surfaces of lower kitchen cabinets or on upholstered and unfinished surfaces of furniture;
    (Wholesome Tip: Do composite samples with furniture, this means you will touch the same tape to multiple pieces of furniture in a room. If mold is found, more tapes can be sent from individual pieces to locate the guilty party).
  • Test furniture bought at a thrift or consignment store or garage sale, pieces that were stored in a basement or storage unit at one time, furniture with an unknown history, or antiques.
  • If you are concerned about a bedroom, sample the bottom of the bed (including wood slats), bottoms and backs of furniture (unfinished surfaces are easier for mold to grow on than finished surfaces), carpet, and under base molding of a common wall with bathroom fixtures.

  • For a basement or crawlspace, test ceiling joists and subflooring, the underside of lower steps, work benches, pressed wood shelving, and contents (furniture, wicker, books, fabric, carpet, etc.) . Mold typically does not grow on concrete, except sometimes you can get some Cladosporium and Aspergillus/Penicillium on darkened efflorescence (mineral deposits on lower foundation walls due to seepage of outside water or water vapor) – correct the condition that contributes to this seepage.  Of course, there are always exceptions.
  • If you have a finished basement, try to get behind lower finished walls for testing (such as from an adjacent area, or through an access panel). You can also wrap tape around a blunt knife and slide it under base molding at several locations.
  • For central air or window units, try to access the coils. Take off a floor vent cover or two and reach deep inside the duct to sample. Sample coils of a dehumidifier if accessible.
  • If testing the attic, sample discolorations:
    • on decking and rafters, especially white fuzz where they meet;
    • on decking (sheathing), especially by soffits and the north side of the roof;
      (Wholesome Tip: If nothing comes off on the tape, the discoloration may not be mold)
  • If you wish, you could skip places where Cladosporium typically grows and which would be homeowner maintenance tasks to clean: refrigerator gaskets, window sills, shower curtains, and bathroom ceilings above the shower. In my experience, Cladosporium growing on surfaces does not easily become airborne and can be wiped off with a little vodka on a microfiber cloth.
  • With front loader washing machines, Aspergillus and Cladosporium sometimes grow on the rubber gasket. Dry after use.”


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