How to Test for Mold

How to Test for MoldThe root cause of the mold must be addressed by finding the areas of moisture intrusion (most often these are not obvious) then repairing, removing and remediating all things contaminated.

FACT: Mold needs a humidity level of 50% or more to grow.

Do you actually know what the humidity levels are in  your home? Hygrometers are small devices that will measure humidity levels and range in price from $7-$30 and are widely available in big-box stores and on the web. Anything that has been wet, water damaged or mold damaged must be removed. (i.e. Sheetrock, paneling, insulation, carpet, cardboard boxes, etc). These items along with the central HVAC unit must be addressed since microscopic mold spores travel on air currents and find air ducts an ideal environment for growth.

Sometimes there has been a flood-type of event that is a one-time deal causing the mold growth. Other times it is a construction issue with plumbing, leaks in roofs, seeping in lower levels, contamination in the HVAC system, even the materials themselves. You need to really look at your own situation and plan accordingly. Be a Sherlock Holmes in your own home!


You cannot thoroughly assess your environmental situation without this data and it would be a waste of time and effort otherwise.  Why spend money on surgery, medications and supplies then choose to NOT breathe clean air as well as recontaminate yourself over and over again?

Mold testing is also your way to confirm or dispute the presence of fungus in the air you breathe. It is a scientific measurement, not a guess. It can tell you exactly which molds/fungi are present and exactly how severe the exposure is AND where the mold is located. It is also your way of knowing when you have accomplished the tasks of successfully removing mold.

There are two kinds of tests: SCREENING which simply shows the presence of mold and DIAGNOSTIC which is sent to a lab who will identify the particular type(s) of mold present.


Expose Mold Test Plates

1. Gather the following:
– Permanent Marker
– Clear Tape
– Clock or Timer (iPhone or egg timer or watch with alarm)s
– Aluminum Foil
– Small Plastic Bag (a grocery bag or small trash bag)
– ladder or step ladder if you are testing inside vents HINT: remove vent faces BEFORE you begin

2. Plan what areas you want to test. Consider testing all the rooms in your home, your crawl space, your attic, and even your vehicles. By testing your entire home or office you gain better information on the pervasiveness of the problem than just testing one or two areas. Mold is often present in rooms you do not suspect.

3. Open individual test plate package. DO NOT open plates until you are ready to put them in the testing area. Place closed plate on testing surface and lift the lid off the bottom of the of the mold media. Flip the lid over and place it upside down next to base. You want to expose the inside of the plate to the air. Repeat for every testing area.

4. Write down time or start timer once all plates are in place. Testing time is one hour.

5. Close the doors to the testing spaces. This helps to isolate the rooms with the greatest problem. Run your AC or heat as normal. This will keep the air moving and give you a measurement that reflects real living conditions.

6. Wait one hour.

7. Place lid back on mold media. Use clear tape to seal the outside rim of the plate shut. On each plate write what room was tested and the date of the test. Wrap plate in aluminum foil (Mold needs to be out of direct light in order to grow). Place plate in plastic bag. Repeat for all plates.

8. Place in warm dry place and wait for 5 days. This is the time needed to grow mold colonies to a size you can see with the naked eye. The temperature needs to be in the range of 68 – 85 degrees to allow the proper incubation.


You can test specific objects (like a sofa or bed) or even pets with a Tap Test using the bottom half of your test plate that has the Agar in it. Turn the plate so that the inside is facing the object you wish to test.  Tap it several times on the test object.  The puff of air that forms as the plate strikes the object will push mold spores into the Agar. This technique tests the collected amount of spores on the surface of the object or pet in questions.  It does not require the one hour exposure and can be sealed up right away.


During the incubation period mold captured in the plate will grow into small round cultures of varying size and color. These colonies are typically dime-size or smaller.  If you get a much larger colony it is usually caused by two spores that have grown together.  Each culture is to be counted.

The severity of your problems is ranked as follows based on the number of cultures:

1 – 2        Low risk of inflammation
3 – 5       Moderate risk of inflammation for low sensitivity sufferers / High risk of inflammation for severe sufferers.
6 – 10    High risk of inflammation to all sufferers
10+       Risk to all persons / Causes autoimmune diseases

Again, the test plates show the PRESENCE of mold and the density.  If you suspect TOXIC mold you should note which area the suspicious mold originated and order a DIAGNOSTIC mold test which will be sent to an independent lab and will verify the type(s) of mold present. These tests are also available on

TIP – Proof of Mold:

Use a camera to document your process. Photos of the plates during the test and then photos of each plate after incubation with its corresponding top that clearly indicates the test location and the date of the test. This is particularly important if you test your work site or need to provide a landlord with documented proof of a mold issue.
how to test for mold
mold plates testing

Once you have completed the clean up, decontamination, etc. you will re-test with the plates to make sure your air is in the range necessary for sinus wellness. Many people think that once they have done the remediation, gotten filters, replaced and/or removed contaminated items and so on that they are done forever. Unfortunately, air quality can change at any given time due to unforeseen situations like a leak, condensation, or some other small situation. If you find you are getting sick again the plates are the only way to know yes or no if there is a problem in your home. From time to time you may begin to have sinus symptoms and problems, when that happens repeat the mold screening process where you had the most problems before.  Test plates and a dated photographic record will help you discern a pattern.