Instructions for Tape Testing for Mold

EnviroHealth Consulting, Inc.
1009 Hemlock Circle, Manheim, PA 17545
Other site:

The instructions below are from 2018. They were updated in March 2022.
The updated instructions are available as a PDF file.

The Four Wheels of Your Home Mold Investigation

Wheel 1:  Take a history.
  • Is your home damp or dry? Is it out in the sun or surrounded by vegetation? Is the relative humidity in the house often elevated? Might there be mold growth on furnishings?
  • Where were past water leaks and floods? Where did the water go? Did the water pass under base molding into wall cavities? Did the leaks stain ceilings?
  • How old is your house? Old houses typically have plaster walls, which mold doesn’t like. Newer houses have drywall (sheetrock), and mold likes the paper backing. In old basements, the ceiling joists and subflooring (above the ceiling joists) may have less nutrient value left for mold than newer wood.
  • Have you fed lunch to mold in the basement by storing vulnerable items down there?
  • Where you do smell mold? (Odors rise.)
    Wheel 2:  Think about where mold might be growing.

If you were mold, where would you look for lunch? Go where the water/dampness is. Basements (structure, contents, and other unpainted wood surfaces), inside sink cabinets, bathroom fixtures, furniture, .

Mold needs food and water (or elevated relative humidity). Mold’s job in nature is to break down organic matter and cellulose. Mold could grow on basement ceiling joists but not usually on concrete foundation walls (unless there is some organic matter in the efflorescence or mineral deposits on the foundation walls). Mold would grow on unfinished surfaces of furniture before it would grow on finished surfaces. Mold would grow on the underside of beds before it could grow on mattresses that were covered with bedding.
If you suspect a damp house with high humidity, test furniture and lower surfaces of bottom kitchen cabinet drawers.

If furniture is of unknown origins (antiques, stored in a relative’s basement, bought at a garage sale or in a re-sale store) is present, tape test. Sometimes mold can grow in strange places, so more and more I have been doing composite samples on major rooms, that is, I touch the tape to multiple surfaces of furniture and baskets, mostly on the undersides but also including upholstered surfaces. Yesterday, as I write this, visible Aspergillus mold was found on the underside of the family’s dining table – no idea why it would have grown there.

Below-grade spaces typically have higher levels of moisture. Check out the basement, crawlspace, and under base molding in a finished below-grade space. Sometimes mold is found under base molding at rooms on ground level, especially if there is a negative grade so that rainwater runs toward the house. To test under base molding, put tape over the end of a blunt kitchen knife and slide the knife/tape under the molding.

Check at AC coils and inside floor vents. (There is an addendum at the end of this document about further tape testing for the heating and air conditioning system.)

If you have a ductless system, unplug it and take off the cover if possible. Tape-sample the coils. If you cannot take off the cover, wrap tape around the end of a blunt kitchen knife and slide it through the fins. Try to tap the coils with the sticky side of the tape. Ductless systems often have mold, and the tough part is that often the other side of the coils is not accessible for cleaning, not even by a mold remediator.

Wheel 3: Draw up a sampling plan based on your hypotheses (educated guesses) of where mold might be found. Where are you going to test?

Try to access unfinished surfaces, which are the first places mold would grow. That is, don’t bother testing painted surfaces (though mold can grow on finished surfaces, too. If there is that much mold, it usually is visible and usually is Aspergillus.). Paint usually has a mildewcide in it, to retard mold growth, so sampling walls may be futile.
In some places tape-testing may not show an issue, such as water-stained ceilings. If water found a quick way out, there might not be much mold in the ceiling cavity. If water just sat up there on the other side of the ceiling, there is probably hidden mold that needs to be remediated. Aspergillus and Penicillium would typically grow in such an area, and these molds can keep growing in just the relative humidity of an unconditioned cavity. The health issue would not be particulate in nature but rather gases penetrating into room air.

Wheel 4:  Take your tape samples.
Instructions for Surface Sampling for Mold

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.

Looking for Sources of Mold Growth by Tape Sampling

Instructions for Tape Sampling

  • Buy 3/4″ clear tape.Get a roll of ¾” inch clear, glossy, transparent tape from Wahlgreen’s Pharmacy (Wexford or Wahlgreen’s brand, only labeled “transparent”), Walmart’s store brand (red and black packaging, transparent), or (3rd choice) Dollar General (dg brand, only “transparent”). Do not use Scotch-brand MultiTask (though we have not checked out their transparent tape yet) if you can avoid it. Too often the glue (with the dust) separates from the cellophane and remains on the bag. All I am left with is a piece of cellophane. Please make a note of what brand tape you are using to help me gauge how well it travels.
  • Please, please, please do NOT send Magic, Invisible, or Satin tape, because the light from the microscope won’t go through the tape, and you may have to do the samples again.
  • Do not use packing tape. The glue may stick to the bag, and the sample will be lost.
  • Stick one end of a 3” piece of tape to your thumb and the other end to your index finger, sticky side out.Press down firmly on the surface you wish to test. Using your index finger to press down gives you good pressure. Just the middle portion of the 3” piece of tape should be exposed. The ends should be clear so that the tape adheres to a microscope slide. Just the middle will be examined under the microscope.
  • Touch the tape to 6-8 spots on the same sort of surface to broaden the data base.Give me something to look at. We are not publishing a scientific paper. We are just interested in “Is there any mold, and is it a lot or a little?”
    Hold to the tape to the light. If you see filmy material on the tape, that could be mold. If you see nothing, then touch the tape to more areas (up to 20) of the same type of material. Lots of times mold is invisible to the naked eye. Send the tape even if you see nothing…but do touch the tape to multiple spots on the same type of surface. If there is only crumbly stuff on the tape, it’s probably not mold. I will brush off the crumbly stuff before putting the tape under the microscope. Light from the microscope won’t go through solids.
  • Sample where mold ISN’T.Knowing where mold isn’t is also useful. Suppose you sampled a discolored area on a basement ceiling joists or subflooring. Even if the sample is positive for mold, was it just that spot or the whole basement ceiling? Can you wipe off the spot or should you remediate the basement?
  • Make a 1/4″ tab on one end of the tape.If you forget to make tabs, try to remove the tape and make the tab. You can’t always get your fingernail under the tape to get it off the plastic mounting surface.
  • Press the tape to the OUTSIDE of a ziplock bag (used as a mounting surface) or similar piece of sturdy flexible plastic (not a baggie).You could even cut off a square of plastic from the bag for a mounting surface. Put the tape on flat, like you were putting a band aide on the surface. Do not fold the tape back on itself. The tape has to be spread out on a microscope slide, over a drop of stain. Line the tapes up on the outside of one bag.
  • Using a permanent marker, write the number of the tape on one end of the tape. The number will match up with your key, showing where the samples were taken. Writing the number on the tape is for quality control purposes, too. The tapes won’t accidentally get mixed up if they have the proper identifying number on them.
  • Make a check out to EnviroHealth.1 sample/$15; 3/$25; 8/$50; 20/$100, more than 20 are $4/sample, added to the initial $100. Once the $100 base fee is paid, future samples are $4 each.
  • Place the plastic bag and key (list of locations sampled) in an envelope and mail with the check to:
    1009 Hemlock Circle
    Manheim, PA 17545

    • Do not require a signature.
    • First class mail is fine. You could cut off the zipper to make the plastic lie flat.
    • Turn-around time is typically 1-2 weeks.
    • Photos of mold under the microscope are included with your report, as are remediation instructions.
    • If you need a rush, please call ahead – 888-735-9649. I may be inspecting out of town.
    • Remember to include your contact information, including name, address, phone number, and email address.
  • More testing tips 



  • 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 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 that water is standing or dripping or where a downspout terminates next to the foundation, test inside under base molding at that area (if the house is on a slab, i.e., the base molding is at ground level).
  • Tip: 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, although sometimes we decide to culture the tape instead of using the microscope. That is, I would touch the tape to a prepared Petri dish and see what grows.
  • 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;
  • Do composite samples with furniture, i.e., 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 in a garage sale or consignment store , 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. There is always the exception, however. An old farmhouse at the edge of a marsh had lots of Aspergillus growing on a rubble foundation.
  • 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 a window unit, 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;
    • 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 off: 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 Borax sprinkled on a damp sponge. Because Cladosporium (and other black molds) can leave a dark stain (due to the melanin that protects it from UV light), you might try spraying the area with Concrobium Mold Stain Eraser.
    • With front loader washing machines, Aspergillus and Cladosporium sometimes grow on the rubber gasket. Dry after use.


I am a former 8th grade science teacher (and Certified Microbial Consultant with the Indoor Air Quality Association) who invites you to work with me in locating and safely getting rid of mold growth or other environmental concerns at your home … including my checking your mailed-in tape samples with a microscope or scheduling an on-site inspection. I’d be happy to work with you in person or through emails and phone calls.

Most of my clients have Lyme disease, chemical and/or mold sensitivities, or other biotoxin illnesses and are concerned about mold in their homes. Many are also concerned with exposure from various types of electromagnetic fields (radiation from electricity, Wi-Fi, etc.) or other environmental pollutants. They want their homes to be a healthy environment for healing, not one where the body is under siege.
With mold, finding the sources of mold growth is central, because without knowing where mold is growing, you can’t eliminate the source of particulates and gases. You can learn to be your own mold inspector by following the instructions for tape-testing that I have listed above. Bear in mind, however, that not all mold can be found by tape-testing. Often I have to drill a small hole in a wall or ceiling or put a tube behind or below sink plumbing for an air sample.

Air samples are important and sometimes essential for finding sources of mold growth. Mold can affect us even if the spores and other particulates cannot reach us. Just the gases that are given off by mold are biologically active and can be harmful.

Obviously you can’t do air samples at home, unless you have the equipment. Gravity plate air sampling is not known for its accuracy, though at times it can be useful. Many people have been unnecessarily concerned by seeing black mold grow on gravity plates. This black mold is typically the common Cladosporium, not Stachybotrys which has sticky spores and does not readily become airborne. Cladosporium blows in from outside and may not be a concern in room air.
Tip:  If you are using gravity plate sampling (such as from a doctor’s office or home supply store), ignore the black and white mold colonies (Cladosporium and sterile fungi, respectively). The ones to count are the green colonies, which typically are Penicillium and/or Aspergillus. No green colonies? Good news…but remember that this type of sampling is typically not very accurate. False negatives can result from gravity plate sampling, but sometimes results reflect a mold concern. Either way, you still have to locate the source of the growth.
Even though I do a lot of air samples (20 or more at the average house, studied in-house, without lab fees), the microscope remains my main tool for on-site investigation.

Is it ideal working through the mail? No, an on-site visit would be better…and I would be happy to schedule an appointment with you for an environmental home inspection. There are very few inspectors out there bringing microscopes to homes…plus checking for gas leaks, telling you what you can do to reduce exposure to various forms of electromagnetic fields (especially AC voltage at sleeping areas and WiFi), checking your vacuum cleaner to confirm that it is not recycling allergens, screening for lead, etc., but you and I can do good work from a distance, too.

If you work with me through the mail, maybe at some point, a local inspector might be scheduled for some follow-up air testing or a duct cleaner might check your AC coils/system. Let’s see how it goes with the tape samples first. Air and dust sampling can confirm that you have mold, but it cannot locate the growth, and again, unless you know where the growth is, you don’t know how to clean it up.

My two websites: is a “decision” website: Who should do the inspection? Who should do the remediation? How can you pick up the slack from a conventional inspector? What pitfalls should you be aware of before interviewing remediation companies? What can you do on your own? What kind of vacuum cleaner should you have? Never trust the vacuum cleaner of a cleaning service unless you have confirmed that it is HEPA. Vacuum cleaners of cleaning services often spread allergens from house to house to house. is an “inspection & information” website. It was set up to parallel what I do on-site and to provide supplementary information. At the “home” tab drop-down (labeled Create Your Healthy Home), there is a description of a typical on-site inspection, should you wish to consider a visit. I often suggest that inspection clients read through this website prior to my visit, because they will have a good background for what we do at their home.

“We” usually means the homeowners and me…because I invite the homeowners to be part of the inspection. They learn to use equipment, see first-hand what exposures are from various types of electromagnetic fields, and conduct parts of the inspection themselves to save time and money. We work together, investigating mold, other indoor air quality issues, gas leaks, water quality issues, and electromagnetic fields. Homeowners learn a lot and typically are glad for the experience…which also empowers them to carry on themselves for the future.

I recently was at a conference where Martin Pall, Ph.D., spoke briefly about his research on intracellular calcium ion exchange…how a very low amount of digital radio frequency (Wi-Fi, cellular, cordless phones) can affect this exchange. Doing what you can to reduce these exposures is recommended, as is reading up on his work and recommendations.

We are all part of a big experiment, because we are all exposed to digital radio frequency. These pulsed signals are new to the human body and we don’t know too much yet about long-term exposure, though we do know that tumors are showing up at the 10 year mark from cell phone use. Will there also be an increase in dementia in those invested in this technology?

Sign up for the free bulletin list at to keep up with the latest information. I try to keep one foot in the 18th century and one in the 21st. At my home, I have minimized exposure to digital radio frequency by hard-wiring my computer, printer, and TV and using a landline phone. My cell phone is in the car, ready for emergency use when traveling.

Another air quality resource to consider is the do-it-yourself lab test from Prism Analytical Labs. For $118 or so, they will send you a pump and testing equipment. You take the air sample and send everything back to them. They screen for 5,000 chemicals, including 21 compounds associated with mold growth (though the mold part of the test is not that sensitive). They give you a report of the total VOCs (volatile organic compounds) and total MVOCs (volatiles produced by mold). Plus, you get a Contaminant Index for your home: what chemicals are irritants or toxins, and what are common sources for these chemicals. If you would like, I would be happy to review results with you, if you ask the lab to send a copy of the report to

For those of you who might take to this type of detective work and may be thinking of a career change, I am working on another website, about learning how to become an environmental home inspector. Please send me an email if you’d like to be notified when that site is up. I may be offering an apprentice-type program…though the new website will be the initial mentor. There’s also nowhere else that I know of to get trained on using a microscope, at least not for our needs. Using the instructions I have posted at, Mold tab, some clients have bought their own microscopes to use at their homes. Please let me know if you’d like your name added to an email list for mold training.

Lastly, we now have a new tool for DNA-level testing for mold, thanks to Dr. Joseph Spurgeon, (If I were contemplating possible legal action relating to mold, I would consider consulting with Dr. Spurgeon and have him oversee the testing of my home, working with a local inspector.) DNA-level testing (similar to the ERMI test scores, which have not been validated by the EPA for home use) uses the same 36 species of the ERMI test but avoids the ERMI (and HERTSMI-2) scoring, which can be misleading. The CAP-14 tests for the top 14 species, which is sufficient and costs half the price of ERMI testing.

Email me for instructions and a Chain of Custody form –

If planning to proceed with CAP testing, order collection containers to collect dust with a vacuum cleaner. The lab will send you the appropriate number of containers, you take the samples, and return them with your check and a filled out Chain of Custody form to the lab. Mark the Chain of Custody form, “Please provide the total weight of the sample.”

Assured Bio, 228 Midway Lane, Suite B, Oak Ridge, TN 37830, 866-547-1727,

2 $75/sample Aureobasidium pullulans

Cladosporium cladosporioides 1


This budget-level choice suggests the relative dampness of your home.
4 $85/sample Aureobasidium pullulans

Cladosporium cladosporioides 1

Penicillium brevicompactum

Penicillium chrysogenum


8 $115/sample Aureobasidium pullulans

Cladosporium cladosporioides 1

Penicillium brevicompactum

Penicillium chrysogenum

Aspergillus niger

Eurotium amstelodami

Aspergillus fumigatus

Stachybotrys chartarum


 If you are mainly concerned with Stachybotrys, 8 species may be sufficient.
14 $140/sample Aureobasidium pullulans

Cladosporium cladosporioides 1

Penicillium brevicompactum

Penicillium chrysogenum

Aspergillus niger

Eurotium amstelodami

Aspergillus fumigatus

Stachybotrys chartarum

Aspergillus flavus

Aspergillus penicillioides

Aspergillus versicolor

Chaetomium globosum

Trichoderma viride

Wallemia sebi


This choice includes the species in the HERTSMI-2 test, with which some of you may be familiar: Stachybotrys, Chaetomium, Wallemia, Aspergillus versicolor, and Aspergillus penicillioides, plus more.
SIM – Survey

Indoor Molds

$249/sample Above, plus remaining

36 ERMI species

This choice provides the most information but does not guarantee that all species that could be an issue at your home will be included. None of these DNA-level tests give you sources of mold growth. Finding the sources is needed before you can decide how to adequately clean up the sources.




I trust this information is enough to get you started…but don’t hesitate to call if you still have questions after reviewing the instructions.


Finally, where do I inspect, if you’d prefer an on-site inspection? I live near Hershey, PA, have a place to stay on Long Island, NY, and often travel in the Metro NY area, plus surrounding states. I also make frequent trips by car to North Charleston, SC, where I conduct inspections for patients of the Center for Occupational and Environmental Medicine, and other medical groups. Inspections are done in central and other southeastern states on the way down and back.

Please do not hesitate to call with sampling questions or for information about scheduling an on-site inspection.
Kind regards,


Further testing of the heating and air conditioning system

Further investigation by certified duct cleaners is recommended (with a strong flashlight). Feel free to send me clear tape samples from any surfaces that do not appear to be clean. Touch the tape to several spots on the same surface, such as from:
AC coils, top and bottom (look under coils, using a camera if necessary

put a camera into the filter bank and into ductwork where accessible
panel insulation
side panels
top panel
blower fins
check under drain pan (often impacted with mold)
in supply plenum
in return plenum
at pie hole – lift up 45% angle and view or take a picture. The pie hole is so the ductwork can go back in.
in boot by register
Check for any fresh air source, particularly if it enters at the return plenum before a filter.
The system should have a 4” pleated media filter.
If not present, perhaps there is room to lift the air handler to insert a filter.

If there is not room to insert a filter under the air handler, then a 5” rack can be placed in the return plenum for a 4” filter.
CAP 14 testing could be done at a supply register. This is DNA-level testing of common contaminant fungi. One drawback is that localized mold at the boot/register may not be adequately differentiated from a contaminated system. The boot is the area behind the register, where dust would collect.

You might HEPA-vacuum and wipe out the boot/register and then run the system for a week or two. Then do a swab and see what you learn. The cost of this test is $140. Email me for instructions and a Chain of Custody form –

Measure the AC temperature at the access hole. It should be about 55 degrees. If there is a new air handler, and the temperature is about 44 degrees, mold could result at the register and in the supply plenum. Dial it down (and remediate the mold).

Putting the fan in the “on” position can help clean the air, as long as the static pressure reading is low at the HVAC system. If it is high, your electric bill could be substantially higher. Static pressure is measured with a pitot and ammeter, possibly by your HVAC contractor.

Or, carefully check your electric bill after the first month of usage to make sure that running the fan constantly won’t drive up the bill.
Depending on a visual examination and the results of tape and/or CAP 14 testing, further recommendations may be made.

Section from May’s report format on HEPA vacuums:

I am not familiar with all the HEPA vacuum cleaners, so feel free to explore beyond this list. “HEPA” stands for “high efficiency particulate arrestance,” meaning, the filter removes 99.97% of particulates 0.3 microns and larger – from the size of mold spores. The chassis must also be sealed, so that particulates do not leak back into room air. If you can, think of a vacuum cleaner as a lifetime investment, and go for the best, especially if folk have asthma, allergies, etc. Getting rid of carpeting is also a good investment.

Avoid vacuums with words like “HEPA-like,” “removes 99.97% of ragweed pollen,” and “for pets.” Be cautious with Hoover, Oreck, Rainbow (unless it has a HEPA filter), Kenmore, and older vacuums.

If you have a long-haired dog, I have been told there is no good HEPA vacuum cleaner for pets. I don’t know about the Nilfisk GM80, if hairs would have to be cut-through.

Consider upgrading your vacuum cleaner to a quality HEPA canister vacuum, such as the Nilfisk GM80 (around $1300, with a better filter than HEPA, known as the ULPA filter, down to 1 micron), a HEPA Miele ($700-800), or on the lower end, an Electrolux Oxygen ($300). The Nilfisk GM80 has a commercial motor, a quality HEPA filter, but no retractable cord.  For carpeting, an optional turbo nozzle may be needed. Both this model and HEPA Miele models test good (close to zero particulates escaping) as measured by a laser particle counter. Miele has a better design for home use. Not all Mieles are HEPA, so double-check before purchase. Miele also has a HEPA upright, with the color yellow or red.

For a bagless upright (bagless is not my first recommendation and should be emptied outside, while you are wearing a mask and standing upwind), there are the Dyson (around $500) and the Shark Navigator ($150-$250).

Some folk purchase the Nilfisk GD930 (around $400), which is used in preliminary cleaning by remediators. It has a commercial motor, a qualityHEPA filter, and a sealed canister. The long cord is not retractable. The downside of this vacuum is that the filter is placed before the motor, so motor dust is given off. The reading with the laser particle counter is not so great, even though we’re not talking about mold particulates being recycled back to room air. This vacuum would be tough with carpeting, because the suction is so strong. You’d need an optional turbo nozzle for carpeting.

See attached for the remediation guidelines from May’s mold report format.

January 16, 2018











Improve your indoor air and water quality and reduce exposure to mold and electromagnetic fields