Promoting and protecting the health and safety of all Idahoans

Frequently Asked Questions About Mold

Click on the questions below to learn more about mold. 

*Note: The Idaho Indoor Environment Program does not test homes/rentals for indoor air pollutants, nor do we address landlord/tenant disputes.

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Molds are fungi that can be found both indoors and outdoors. No one knows how many species of fungi exist but estimates range from tens of thousands to perhaps three hundred thousand or more. Molds grow best in warm, damp, and humid conditions, and spread and reproduce by making spores. Mold spores can survive harsh environmental conditions, such as dry conditions, that do not support normal mold growth.

Molds are found in virtually every environment and can be detected, both indoors and outdoors, year round. Mold growth is encouraged by warm and humid conditions. Outdoors they can be found in shady, damp areas or places where leaves or other vegetation is decomposing. Indoors they can be found where humidity levels are high, such as basements or showers.

Mold can grow if it has moisture and a food source (e.g. wood, drywall, leaves etc.).

Most people do not appear to be affected by everyday exposure to mold. However, people who have allergies, asthma or weakened immune systems may be more sensitive to molds than others. People exposed to molds may experience symptoms such as a runny nose, sneezing, watery eyes, skin rash, headaches or difficulty breathing.  If you or your family members have health problems that you think are caused by mold, talk to your doctor.

Testing for mold is not necessary. You can typically see or smell mold. Mold comes in many different colors.  It may appear as small black, yellow, green or white specks along your bathroom or basement walls.  In some cases, mold may not be visible.  You will, however, be able to smell it.  Mold has a very distinctive musty odor.  If you smell a suspicious odor, trace it to the source.  You may discover mold growing behind a wall or under a carpet.

There is not a practical way to get rid of all indoor mold spores, but you can prevent and control mold growth indoors by controlling moisture. 

  • Stop water leaks, repair leaky roofs and plumbing immediately.

  • Open windows and doors to increase air flow.

  • Install exhaust fans in bathrooms, kitchens and laundry rooms and use them whenever the room is in use.

  • Ventilate and insulate attic and crawl spaces.

  • Clean and dry water damaged carpets, clothing, bedding and furniture within 24 to 48 hours.

  • Vacuum and clean regularly to remove mold spores.

  • Check for signs of condensation around windows. Wipe up water immediately to prevent mold growth.

All mold cleanup methods are the same, regardless of mold type.  To clean up and remove mold growth, follow these steps as they apply to your home:

1. Identify and fix the moisture problem- The most important step in mold cleanup is to identify and correct the source of moisture that contributed to mold growth.  If the source of moisture is not stopped the mold will come back. 

2. Size the moldy area- If the area is larger than ten square feet, consider hiring a cleaning professional.  To locate cleaning professionals in your area, check under Fire and Water Damage Restoration in your Yellow Pages.  

3. Take action to protect yourself- During cleanup, the number of mold spores in the air increases greatly.  Consider using personal protective equipment when handling or working around mold contaminated materials.  Rubber gloves, goggles, protective outer clothing and a respirator will minimize your exposure.  

4. Begin drying all wet materials- Begin drying wet materials as soon as possible after becoming wet. Move wet items away from walls and off floors.  In severe cases, fans and dehumidifiers may be used.

5. Clean surfaces- Mold growing on the surface of non-porous materials such as hard plastic, glass, metal and solid wood can usually be cleaned.  Thoroughly scrub contaminated surfaces with a stiff brush and mild detergent solution.  Then, rinse and allow them to dry. Launder clothes, bedding and other washable materials.  For beds, sofas and other furniture that are not washable, consider vacuuming and allowing them to dry out.  Throw the item out if mold begins to grow inside or outside the item.

6. Disinfect surfaces- A disinfectant may be used to kill mold missed by cleaning.  Mix ¼ to ½ cup bleach per gallon of water.  Apply to hard surfaces where mold growth was visible before cleaning.  Allow to dry. (Don’t mix bleach with ammonia.)

7. Monitor- Continue looking for signs of moisture problems or new mold growth.  If mold returns, repeat cleaning steps.  Regrowth may be a signal that the material should be removed or that moisture is not under control.


No, IDHW does not perform tests or inspections of homes for mold problems.  We respond to requests for assistance by providing information and recommendations on how to treat and prevent the potential health effects of mold.

There are no federal or State of Idaho regulations regarding mold inspection requirements or mold cleanup. 

Mold problems in buildings are a result of moisture problems.  Excess moisture can come from leaks and condensation.  Tenants and landlords both have responsibilities for addressing water and moisture problems that can cause mold.  Generally, fixing leaks is the landlord’s responsibility but reducing condensation is the renter’s responsibility.  Sometimes maintenance issues can become landlord and renter rights issues.  See Idaho Legal Aid's Landlord-Tenants Rights and Responsibilities for more information. 

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