Is Dormant or ‘Dead’ Mold Dangerous?

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Dormant mold is mold that isn’t actively growing but which can still cause symptoms and problems if kicked up, disturbed, or distributed.

Mold becomes dormant most often because the source of water that caused it to grow eventually dries up.

But dormant mold isn’t dead — and it can “come back to life” if given moisture or water.

And, even if it does not “come back to life” or become viable again, dormant mold can still cause problems and be dangerous.

“Removal and cleaning are important because even dead mold may cause allergic reactions in some people.“

U.S. Centers for Disease Control, “Mold After a Disaster,” July 28, 2020 (Emphasis added).

Mold can be classified as viable, or as dormant (non-viable), and as allergenic, pathogenic, or toxigenic.

Mold spores can lie inactive for an extended period when conditions are not conducive to their growth—such as in dry or cold environments, or when moisture and humidity levels fall below 60%.

Mold requires moisture, a food source such as wood, paper, or other organic material, and suitable temperatures to grow and thrive.

Dormant mold becomes viable again with moisture.

You can think of mold spores as tiny grass seeds.

And think of dormant mold like grass that turns brown in the off-season: It may look dead, but when spring comes around, it comes right “back to life,” and turns green again.

That’s because—just like the mold spores—the grass wasn’t dead to begin with, it just lacked the water and sunlight it needed to grow.

So, yes, dormant mold can be a problem. And because mold spores are allergenic, pathogenic, or toxigenic, releasing them into the air in any state—dead, dormant, or viable—can cause allergic and other reactions.

When environmental conditions change and become more favorable—i.e., when there is an increase in moisture—dormant mold spores can become active again and begin to grow and multiply.

Dormant mold can bloom ‘overnight’

This is a common and specific reason why mold can seem to appear suddenly after a water leak, flood, or an increase in humidity.

Dormant mold is significant because it means that even if you don’t see active mold growth, the potential for mold development still exists if the environmental conditions change.

If your plumbing springs a leak, or water drips down a wall, enters through a window, or humidity increases, mold will become an even more noticeable problem.

A rough analogy might be dust turning to dirt: It accumulates, becomes more visible, and can be tracked through the house more noticeably.

As dust (dormant mold), these things still occurred, they were just less obvious.

Solution to dormant mold is removal

To manage dormant mold spores and prevent them from becoming a problem, you should:

1. Dust and vacuum often, or hire a house cleaner. Mold loves dust, dander, and dirt.
2. Keep indoor humidity levels below 60%.
3. Fix leaks, floods, and water intrusion issues immediately and fully.
4. Have proper ventilation in moisture-prone areas like bathrooms, kitchens, and laundry rooms.
5. Use dehumidifiers in damp areas or during humid seasons.
6. Regularly clean and maintain HVAC systems.
7. Keep your windows closed if outdoor humidity is higher than about 50-60%.
8. Run ceiling fans to circulate air.
9. Remove the mold, no matter what state it’s in, and with proper PPE. If mold is a problem in your home, it is best to hire a professional mold remediation company that can correct the cause of the problem so it’s handled for good. Because mold is either allergenic, pathogenic, or toxigenic, hiring a professional is also the best choice for your health.

Even if mold is currently dormant, it can still potentially cause health issues for sensitive individuals if they inhale or come into contact with the spores.

For help dealing with mold in any of its growth phases, contact Mold Solutions for a free environmental consultation.