How to: testing & sampling of black toxic mold

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How to: testing & sampling of black toxic mold
Mold is a health hazard. (Fortress inside image by FaithBuffy from

Mold in a building poses health risks and can trigger symptoms ranging from headaches to respiratory problems. In rare cases, mould, especially the toxic black mould (Stachybotrys chartarum), causes fatal complications. You can do preliminary tests yourself to determine whether a building has a serious mould problem that requires further investigation and action. Test the air, then locate growing mould and take samples for more accurate identification.

Skill level:

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Things you need

  • Mold test kits
  • Flashlight
  • Surgical gloves

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  1. 1

    Set up the petri dishes from mould test kits intended to test the air in each room of the building. Use another test kit just outside the building as a control.

  2. 2

    Leave the dishes exposed to the air according to directions, usually for up to an hour.

  3. 3

    Seal the dishes and leave in a warm place for one to two days.

  4. 4

    Examine the petri dishes to see if fungus has developed and compare dishes inside to the one outside. Fungus indicates mould spores are present in the air and a noticeable difference between the dishes shows which rooms have a high level of mould spores.

  1. 1

    Search the rooms showing high levels of mould to find the source, using a flashlight if necessary. The growing mould may be inside crawl spaces or underneath furniture.

  2. 2

    Put on the surgical gloves.

  3. 3

    Wipe the mould with the swab from the kit.

  4. 4

    Swill the end of the swab in the solution according to kit directions.

  5. 5

    Insert the indicator strip in the solution, which will indicate if the mould is the dangerous Stachybotrys chartarum.

Tips and warnings

  • Treat mould by first cleaning all visible mould with a bleach solution, then reduce humidity. A dehumidifier removes moisture from the air but something as simple as locating and fixing leaks and drips may be all that is needed.
  • Home test kits are fine for a preliminary investigation but for accurate results, a laboratory needs to process the samples. Plenty of commercial laboratories do mould tests and they can give you detailed instructions on how to take the samples.
  • If people in the building are showing severe symptoms, get medical assistance and contact professionals to test and clean the building.

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