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Where does mold grow and how to remove it from your home and possessions?

Summary

Whether you are staying in your current home or moving to another one, to create a mold-free indoor environment, you must:

  • First make the environment inhospitable to mold
  • Remove the existing mold
  • Remove the existing mycotoxins

My credentials:

  • BS in Microbiology
  • PhD in Biochemistry
  • Taught Microbiology at the University level
  • A scientist with active microbiology and clinical labs for 15+ years at multiple institutions

Why mold often grows back?

  • Mold is a living microorganism. If conditions remain favorable for its growth, it will likely grow back, even after thorough cleaning or remediation. The reason is that mold spores are likely everywhere, and just a single microscopic spore can come back to the cleaned/remediated area and grow.
  • For example, let's say you have condensation next to a window and you notice mold growth. You remove 99.9% of the mold. However, if you don't remove the source of the condensation, the mold will grow back in a few weeks. Even if you remove 100% of the mold at that spot, mold spores are likely nearby, and they will come back and grow.

How to ensure mold does not grow back?

  • You must identify conditions that enable mold growth and change them:
    • If your indoor humidity is greater than 50%:
      • You can get a dehumidifier to keep it at 50%.
      • If your house is too big for a portable dehumidifier, you can get a whole house dehumidifier.
      • You can get an AC/furnace unit that has a dehumidifier function (it uses the AC to dehumidify).
      • One other possibility is to run the AC for 10 min 2-3 times a day to dehumidify the house (you can do this in winter as well; just re-heat the house afterwards).
    • If you have a water leak, you must fix it immediately, then remediate the area (drying the area, at a minimum).
    • If you splash water while bathing/showering/doing dishes, and it goes onto the floor, you have to find a way to prevent that or clean it up quickly. A simple washable cotton rug will do it. If the molding is not caulked to the floor, the water may go into the wall and enable mold growth. You can caulk the molding to the floor using clear silicone caulk.
    • If you get condensation in an area, you:
      • Have to add a ventilation mechanism to prevent it
      • Should keep the room warmer (cold walls will condense water). For example, if you shower in the morning when the walls are cold, that may cause condensation on the bathroom walls - pre-warm the whole house or just the bathroom before showering.
    • You may have mold growing inside the walls if your fresh air intake and trickle vents are not working (see below for explanation)
  • After you have made your indoor environment unsuitable for mold growth, removing the mold will be a long-lasting strategy because it will not be able to grow back.
  • I recommend using bleach to remove mold, even on porous surfaces like wood. Here is more info on bleach and mold (and why bleach is better than ammonia). Yes, I know the internet is full of myths about how you should not use bleach, but it's just that - a myth, propagated by people who have read it on the internet.

Where does mold grow and how to find it? 

Mold can grow anywhere where there is food for it (wood, paper on drywall, human food particles...) and enough moisture. The most common places are:

  • Behind the walls, due to water leaks or water condensation (see below how condensation can be created inside the walls).
  • On your walls. For example in the kitchen and bathroom, if they are not properly warmed and/or vented.
  • In your crawlspace
  • In your attic
  • Inside your dishwasher and/or food disposal (see below for an entire section)
  • Inside your HVAC
  • Below your floorboards 

Mold behind walls/floorboards, etc.

  • You will have to suspect that there is mold there (due to water leaks, black stuff coming out, or pure guess)
  • You will need to remove some drywall or floorboards to take a look
  • You will need to test for mold (this is very challenging today, which is frustrating)
  • If you find mold, you will need to remediate or have it remediated

Mold inside your dishwasher and/or food disposal

  • If mold is growing in the dishwasher or food disposal, consider getting rid of them.
  • A food disposal can be cleaned with bleach, but mold will likely come back. Removing the food disposal and replacing it with a normal drain and pipes is easy, then just put food in the trash or composting bin.
  • A dishwasher can have mold growth behind the gasket that is at the bottom of the door. This gasket normally keeps the water inside the dishwasher. However, over time, the gasket can leak and allow food to go inside the dishwasher door, feeding the mold there. It is difficult to find it. You have to stick your head inside the dishwasher and look inside the opening at the bottom of the door. You can also stick your finger in that opening and check if there is anything there.
  • You may want/need to replace the drain hose from the dishwasher, as it may harbor mold
  • Once you are convinced that the dishwasher is free of mold, wash all your kitchen items twice

 HVAC, trickle vents, fresh air intake, air filters, etc.

  • Trickle vents and fresh air intake are very important to prevent condensation and mold growth inside your walls, which is very difficult to detect and costly to remediate.
    • When your house is colder than the outside air, if the outside air is forced to enter your house through the walls, it will cause condensation and mold growth inside the walls. 
    • How does the outside air go through your walls? You create a negative pressure inside the house whenever you run exhaust fans (like the bathroom vents, kitchen hood...). And you need to use these to get rid of the moisture created by showering and cooking.
    • Trickle vents (small openings above windows) and fresh air intake (connected directly to your HVAC from the outside) allow air to come in from the outside without going through the walls.
  • The HVAC can both grow and spread mold.
    • The AC has a condenser that provides plenty of moisture, so mold may grow if it has something organic to feed on (for example, aerosolization of food during cooking, which is why you should run the kitchen hood whenever you cook).
    • The HVAC can suck mold in and spread it around the house.
    • If you suspect your HVAC is contaminated with mold, you will likely need to have a professional cleaning.
  • Air filters can minimize the spread of mold, and potentially mycotoxins, by the HVAC
    • If you only have one air return, I recommend using a high quality filter with as high MERV rating as your HVAC can handle, hopefully 11 or higher. This will minimize the spread of mold by the HVAC.
    • If you have two air returns, I recommend placing a charcoal filter on the second one. If mycotoxins are being released in one part of the house, this will minimize their spread.

Install portable air purifiers and add charcoal bags

  • While there are specialty air purifiers targeted to moldies, these cost a lot of money.
  • I recommend simple HEPA air purifiers, usually under $100, that have a cavity inside. The HEPA filter will take care of any mold. You can place large bags (very cheap) of activated charcoal inside the purifier cavity, and this will also capture any floating mycotoxins. HEPA filters remove molds very effectively (see reference below).
  • Here is one that has a HEPA and activated charcoal filter.
  • Also buy activated charcoal bags (super cheap) and hang them all over the house, to capture any floating mycotoxins.

Removing mold and mycotoxins from hard surfaces

  • Mold and likely mycotoxins can be removed from hard surfaces, even porous ones, using bleach. This includes most furniture, cabinets, appliances, toys, other household items.
  • I wrote an article on how to do this and why bleach is better than ammonia HERE.

Removing mold and mycotoxins from washable items (clothes, sheets, pillow cases...):

  • Wash these items with lots of detergent (5 times more than normal).
  • For whites, use bleach.
  • Without removing the items from the washer, wash them again with the normal amount of detergent.

Non-washable items:

  • Carpets, upholstery, and car interiors: these are some of the toughest items, as they are not easy to remove or replace, but are also very hard to clean. To remove both mold and the mycotoxins at the same time, I recommend the steps below. You should first test this procedure in a corner, to ensure it does not permanently stain your carpet:
  • Pillows: I would throw them away and replace them


References:

 

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Comments

  1. UnknownDecember 23, 2020 at 6:25 PM

    Do you have a reference for the claim that charcoal will absorb mycotoxins? Tia

    ReplyDelete
  2. Momo VuyisichJanuary 3, 2021 at 9:14 PM

    Good question. I updated the article with several references on that topic. Please reload the page to see them. Cheers.

    ReplyDelete

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