Least-Toxic Control of Mold Choose a different pests

Factsheet: When Mold Attacks: Strategies to Prevent, Detect and Control Mold in Your Home


Pest type: Fungi

Telltale signs of mold presence include a musty or earthy smell, or stains on drywall, trim and foundation walls. Also keep an eye out for rust on plumbing underneath sinks, and behind washing machines and refrigerators with icemakers. Mold can be visible on walls, in tubs and other damp areas. It can also occur where you cannot see it, such as behind wallpaper, and inside wall cavities and heating ducts, in ceiling tiles, carpet backing, gypsum board and wood materials that have become moist. If you suspect that mold is hidden, do not investigate yourself! Hiring a professional will avoid an unintended release of a mass amount of mold spores. Some companies use specially trained dogs to pinpoint the source of mold growth that cannot be readily seen.

Is it a problem?

If a mold’s spores produce chemicals called mycotoxins, the mold is categorized as “toxic.” However, other molds that do not release mycotoxins can still be a health threat, and are much more common in the home. Of the 100,000 types of mold that exist, only a few dozen are categorized as “toxic.”

Examples include Penicillium, Aspergillus, Stachybotrys, Paecilomyces and Fusarium. Toxic molds are found in about two to five percent of American homes. Molds are categorized as fungi, just like mushrooms, mildews, rusts, and smuts, because they are in a group of plants that do not contain chlorophyll and collect nutrients from organic matter. Today’s wallboard in homes can contain a percentage of material used as nutrients for fungi, including recycled paper, starch and paraffin. A mature mold generates spores, which are light and float in the air until settling on a surface. Unlike other molds, toxic mold is not the kind found in bathroom sinks and tubs. It actually develops behind wall-paper, in ceiling tiles, carpet backing, gypsum board and wood materials that have become moist or humid (not necessarily saturated) in an environment between approximately 40 and 100 degrees Fahrenheit.

Pest prevention practices

Remove sources of water/moisture

Keep the home ventilated by venting bathrooms and rooms with dryers to the outside, using exhaust fans when cooking or dishwashing, and using dehumidifiers and air conditioners.

Run the fan in your air conditioner for 30 minutes after turning it off to dry out the inside of it.

If you have a forced air heating and air conditioning system, clean filters regularly. Increase circulation in the home by keeping doors between rooms open.

Add insulation to cold surfaces like windows, piping, exterior walls, roofs or floors in order to prevent condensation. 

Grade soil away from the house.

Fix any leaks. 

Regularly clean and repair roof gutters.

In-Depth Information:
Understanding where mold likes to grow is the first step to prevention. Is the inside of your home susceptible to mold growth? Mold can materialize anywhere there is dampness or relatively high humidity. Air has less ability to hold moisture as the temperature decreases. To measure levels in your home, you can purchase an indoor humidity meter for around $10 at most hardware stores. If you want to control mold, you must control the moisture in your home.

When building a new home, or replacing any sections, use a non-cellulose, low-nitrogen material. These materials are less likely to trap water and stay damp. When water invades your home, take steps to keep mold from following. If an area in your home has been water damaged, take immediate steps to clean and begin drying it out within 24 to 48 hours. It might be necessary to remove wallboards and flooring materials to accomplish this process. Wash off water-damaged surfaces with detergent and water, then dry completely. Use fans, dehumidifiers, and air conditioners to dry. When using a dehumidifier, empty the water collection pan frequently. If you live in a dry climate, open the window to help dry out the material. Drying may take several weeks or months to achieve. Replace porous materials like rugs, mattresses and draperies. However, if there is only limited and recent damage, a few hours sitting in sunlight might take care of the problem. Any wet insulation should be discarded and replaced.

Monitoring and record-keeping

Do you need air samples? If mold is visible, you know you have to address the problem; sampling is not needed. Factors such as heating or air conditioning systems, use of vacuum cleaners, and opening and closing doors and even switching on a light can change mold levels dramatically in one specific area, and can throw off an air sample. Since these tests are often unreliable, do not depend on one or only several tests. Hire a professional industrial hygienist or home inspector experienced in microbial testing. The National Allergy Bureau considers mold counts in air of 0-900 mold spores per cubic meter as low, 900 to 2500 as moderate, 2500 to 25,000 as high, and above 25,000 as very high. However, opinions on this vary widely, as do individual sensitivities.

Non-chemical and mechanical controls

Prep work: Separate your cleanup area from other areas of the house by hanging plastic sheeting to prevent mold spores from spreading. Gear yourself up with goggles without ventilation holes, gloves that reach mid-arm, long sleeves and pants. A respirator designed for particle removal for protectino against inhaling mold spores is also necessary. You can find these respirators at most hardwood stores.

Clean up: Scrub mold off surfaces with detergent and water, then dry completely. If the contaminated area is metal, glass or any other non-porous material, these can usually be restored. If you are cleaning a semi-porous item like wood or concrete, use cleaning pads or stiff brushes for the cleaning process. Porous objects like carpets and insulation will most likely have to be discarded. If an object you hold near and dear to you is contaminated, try contacting a professional skilled in restoration work. Keep in mind that an area of mold should be removed even if it is dead. It can still release spores that may cause allergic reactions in some people. 

Aftermath: Remove and wash your clothes immediately after you finish cleaning. Rags, brushes and anything else that came in contact with mold should be placed in airtight plastic bags and discarded.

Prevent Mold from Returning: With an effective cleanup, you can greatly reduce mold presence. To keep the mold from striking again, it is critical to address the moisture source. When appropriate, replace damaged materials with non-cellulose, low-nitrogen content materials.

In-Depth Information:
For cleaning up existing mold according to the Environmental Protection Agency (EPA), chemical use to kill molds is not recommended. Chemicals aside, inhaling mold spores can pose a serious health threat. If you have allergies or experience any reaction when dealing with mold, contact a professional to take care of the problem. 

Biological controls

Biological methods are not effective for controlling mold.

Least-toxic chemical options as a last resort

Control should be taken through cleaning, see above.

Acetic Acid (Vinegar)

Boric Acid


Chemicals to Avoid

Look at your product labels and try to avoid products containing those chemicals listed below:

(A = acute health effects, C = chronic health effects, SW = surface water contaminant, GW = ground water contaminant, W = wildlife poison, B = bee poison, LT = long-range transport)

Alkyl dimethyl benzyl ammonium chloride (ADBAC) (A, W)

Benomyl (C, GW, W)

Difenoconazole (C, W)

Mancozeb (C, W, B)

Metalaxyl (A, C, W)

Penthiopyrad (A, C, GW, W)

Propiconazole (A, C, W)

Tebuconazole (A, C)

Tridemorph (A, C, W)

Vinclozolin (C, W)

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