Gravity plate testing -
the most common test kits.
(What not to do)
Many readers will think about buying a mold test kit and setting it out for an air sample. The typical mold test kits are known as settle plates or gravity plate tests. A settle or gravity plate is a Petri dish with nutrient in the base.
After the top of the Petri dish is removed, floating spores "settle" into the plate and start to grow on the nutrient gel on the bottom. After some days, the mold colonies become visible and can be identified and counted.
This common type of mold test kit is not known for its accuracy. In fact, some of the lightest spores (which are also some of the most important spores) may not settle down for 4-8 hours or more. If you're exposing the Petri dish for one hour, you could miss most of the count for Aspergillus and Penicillium spores.
This type of mold test kit won't work for testing Stachybotrys, the "toxic black mold," for two reasons:
- Stachybotrys spores are sticky. They don't become airborne as easily as the spores of other types of mold. That's good news for you, but bad news for air testing.
- Stachybotrys prefers food known as CMA
(cornmeal agar) rather than the nutrient typically used in prepared Petri dishes (MEA, or malt extract agar). You can't buy prepared CMA Petri dishes without first jumping through some hoops.
Stachybotrys is nevertheless easy to test for. All you need to do is touch some clear, glossy sticky tape to the suspect surface and send the tape to a testing service for examination under a microscope. You can do tape testing for any suspect surface, even without black mold visible. The surface could appear perfectly clean and still have high levels of mold.
You could either go to the website of the American Industrial Hygiene Association, www.aiha.org, to look for a certified microbiology laboratory or you could work with a discount screening surface such as we offer. If you decide to work with a laboratory found at the IAQA website, then call the laboratory for their instructions on how to sample. The lab I work with is QLab, www.qlabusa.com, info@QLabUSA.com, 1-856-489-0011, Wei Tang, Ph.D., microbiologist.
Stachybotrys spores look like black grapes, and they are just about the only common mold spores that look like black grapes. Feel free to send your samples to EnviroHealth Consulting, and we will be happy to provide timely feedback on the presence or absence of Stachybotrys or other kinds of mold.
Please note: If you require results for legal purposes, you are advised to work with a certified microbiology laboratory.
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EnviroHealth discount fees:
$15 - 1 tape sample
$25 - 3 tape samples
$50 - 8 tape samples
Optional fees:
$25 - if a letter is needed, such as to a landlord.
$50 - if a clean up protocol is requested, based on findings from the tapes.
Our sampling instructions for using the EnviroHealth testing surface:
- Purchase a 3/4" roll of Scotch-brand MultiTask tape. This can be found in any office supply store. Do NOT use Magic Tape or Transparent Tape or any other kind of Scotch tape. The light from the microscope has to be able to pass easily through the tape, or all we will see will be a cloudy scene. You need to use clear, glossy tape.
- Hold the ends of the 3-inch piece of tape with two fingers of one hand. The sticky side of the tape should face away from you.
- Touch just the middle (about a half inch) of the tape to the suspect surface.
- Fold back one end of the tape to make a small tab (to help staff remove the tape from the plastic).
- Lay a piece of tape out flat on the OUTSIDE of a plastic bag. Think of putting a Band-Aid on the bag. The tape needs to stick to the bag. When EnviroHealth staff peels the tape off the bag, the mold spores will stick to the tape, not to the bag. Here are a few "Do Nots":
Do not make a loop of tape and stick the loop on the plastic bag.
Do not place the tape inside the bag.
Do not fold the tape back on itself.
- If you're in doubt about your arrangement of tape with
bag, try to peel off the tape yourself and see if it's easy to do. You can always smooth the tape back on the bag.
- Identify where the sample is from. If you are sending several samples, you could number them on the bag and then provide a written list of locations.
- Send the bag (or cut off the part of the bag where the tape is) to EnviroHealth, 7104 Red Top Road, Hummelstown, PA 17036, with a check made out to EnviroHealth. Make sure to include your contact information.
- Within a few days after receiving the tape, we will let you know if the sample shows toxic black mold or some other kind of mold.
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