About Mold

Molds and fungi are naturally-occurring organisms that can be found everywhere, both indoors and out. Humans do not live in a mold-free environment, nor would we want to. Molds are a necessary part of our natural environment.

Problems occur, however, when conditions indoors allow for excessive mold growth. The primary culprit for this excessive growth is excess moisture. No excess moisture = no excess mold growth. Maintaining your home or building to prevent excess moisture and properly fixing moisture problems when they do occur are the keys to preventing both structural damage to the building as well as the risk of health problems to those living and working in the building.

The internet offers thousands of sites on mold and the effect of mold on health. The links contained on this site offer highly credible, well-researched, scientifically-based guidance.

In this document:

General Web Resources on Mold

The Effect of Mold on Health

Cleaning Up a Mold Problem

Testing for Mold

Resources for Physicians

Frequently Asked Questions:

  • Can I Clean Up a Mold Problem By Myself?
  • Can I Use Bleach?
  • My Apartment Has Mold. What Can I Do?
  • I Have a New Home With Mold. What Can I Do?
  • I Have Basement Living Space. Will I Have a Mold Problem?
  • My Workplace Has a Mold Problem. What can I Do?
  • Where Can I Find a Mold Remediation Professional?


Building Science Corporation:

Look specifically for these documents:

Environmental Protection Agency: General Mold Resource Page

Plus, the following excellent general guidance documents:

A Brief Guide to Mold, Moisture and Your Home and
Mold Remediation in Schools and Commercial Buildings


Lots of media attention is given to the effect of mold on human health. When dealing with a mold problem in your home or building, it is important to remember don’t panic. The national Centers for Disease Control & Prevention states that exposure to damp and moldy environments may cause a variety of health effects, or none at all. Some people are sensitive to molds. For these people, molds can cause nasal stuffiness, throat irritation, coughing or wheezing, eye irritation, or, in some cases, skin irritation. People with mold allergies may have more severe reactions. Mold is a common trigger for those with asthma. Immune-compromised people and people with chronic lung illnesses, such as obstructive lung disease, may get serious infections in their lungs when they are exposed to mold.

A link between other health effects such as bleeding lung, memory loss, or lethargy, and molds, has not been proven. Further studies are needed to find out what causes these other adverse health effects. Efforts are being undertaken nationwide to determine how much mold exposure is too much mold exposure. Until this can be scientifically determined, however, the Maine Indoor Air Quality Council recommends a preventive approach: keeping your home or building free of excess moisture and fixing moisture problems when they occur will minimize the risk of any health problems from mold exposure. Again, no excess moisture = no excess mold growth.

The following resource provides comprehensive information about the effect of mold on health:

U.S. Centers for Disease Control & Prevention – General information on mold and various mold species, as well as a recently released article on the state of mold science and health.

Building Science Corporation: Mold: Causes, Health Effects and Clean-Up

Remediating (cleaning-up or fixing) a mold problem:

The approach to solve a mold problem in a building is fairly simple.

First, fix the moisture problem. Since excessive mold growth indoors is a result of excess moisture, finding and fixing the moisture problem is the necessary first step towards fixing a mold problem.

Second, clean up the mold. Depending on the extent of mold contamination, building owners and managers can either tackle the problem themselves, or hire a professional.

The following resources contain information about how to safely and effectively clean up a mold problem in a building.

Building Science Corporation: Mold Remediation in Occupied Homes

Virginia Cooperative Extension Service: Mold Remediation

U.S. Environmental Protection Agency: A Brief Guide to Mold, Moisture and Your Home

The following guides, while primarily designed for building managers, custodians, and others who are responsible for large, commercial and institutional buildings, are also useful for individuals looking to hire a professional to handle a remediation. Contractors and other professionals who respond to mold and moisture situations will want to use and/or refer to these and other similar, professional guidelines.

U.S. Environmental Protection Agency: Mold Remediation in Schools and Commercial Buildings

New York City Department of Health: Guidelines on Assessment and Remediation of Fungi in Indoor Environments

Testing for mold:

One of the most common questions asked by Maine building owners and occupants is: do I need to test my home or building for mold? Because mold is everywhere in our environment, both indoors and out, testing for mold is not as much a process of testing for the presence of mold, but rather a process to test for the species of molds and the quantity of molds present at the point the test is taken.

Building owners and occupants should ask themselves whether or not having knowledge of the species and quantity of mold is useful to them to help solve their mold problem or indoor air quality concern. In many instances, building owners and occupants have already identified a clearly defined moisture problem, and have visible evidence of resulting mold growth (they can see it or smell it.) In these cases, it would not likely be necessary to conduct a test. The building owner or manager should follow the guidance referenced above to fix the moisture problem and clean-up the mold properly.

When health problems from mold exposure are suspected; when you can’t see or smell mold but suspect the presence of mold; or when the extent of mold damage needs to be determined; testing may be useful.

The following resources can help determine when it is useful to test for mold:

Maine Indoor Air Quality Council: Guidance for Determining When to Conduct an IAQ Test

Building Science Corporation: Mold Testing


The U.S. EPA, in partnership with the University of Connecticut Health Center, has developed an excellent guidance document for health professionals to assist in the recognition and management of health effects from mold exposure. The document is available as a free PDF download.


Q. I have mold growing in my bathroom (or another area of my home). Can I clean it up myself?

A. Yes, most smaller mold problems (less than ten square feet) can be easily cleaned by a homeowner. Remember to first fix the reason why the excess mold growth occurred. Then clean the mold. Soap and water and elbow grease are very effective at cleaning mold. Avoid spreading mold spores and particles during the clean-up by using strategies similar to those used prevent the spread of fine dust particles (such as dry wall dust): keep things contained, bag everything in plastic before moving it from the work site, turn off the furnace or air conditioner while working, and wear an N95 mask (available at your local hardware store.)

Larger mold problems (more than 10 square feet) can be addressed either by the homeowner or a contractor. Be sure to follow the guidance contained in the U.S. EPA’s Guide to Mold Remediation in Schools and Commercial Buildings (even if the mold problem is in a home).

Q. Can I Use Bleach to Clean Up Mold?

A. Cleaning up mold with soap and water is preferred. A mild solution of bleach (no more than one cup per gallon of water) will effectively kill mold spores but not necessarily remove the spores imbedded in porous surfaces. Use bleach in accordance with the manufacturer’s instructions, open windows, and wear protective gloves and eyewear. If you are hiring someone to clean the mold up for you, they must be a licensed Maine pesticides applicator in order to use any chemical, including bleach, to clean, control, or kill molds. After cleaning mold, vacuum the area using a vacuum with a HEPA filter.

Q. I live in an apartment, and my landlord didn’t fix a water problem. Now there is mold. What can I do?

A. Preventing mold in an apartment is a responsibility shared by both you and your landlord. Download our free Guidance for Addressing Mold & Moisture Problems in Rental Properties to guide both you and your landlord through a best practice process to resolve the issue.  Other resources:  Use the Tenant’s Checklist to Prevent Mold in Apartments to better manage the risk of moisture problems in your living space. Provide your landlord with a printed copy of the following: Landlord’s Checklist to Prevent Mold in Apartments; the article titled: Mold: Causes, Health Effect & Clean-up offered by the Building Science Corporation as well as a copy of the U.S. EPA document: A Brief Guide to Mold, Moisture & Your Home. Your landlord is required by law to provide you with a safe and healthy living environment. If you don’t believe your landlord is providing you with a safe and healthy living environment, you can do the following:

1) Know your rights. You can obtain a consumer law guide through the Maine Department of the Attorney General (207-626-8800); review Maine’s Landlord-Tenant Laws or view an On-Line Handbook for Tenant’s Rights at Pine Tree Legal Assistance.

2) Ask the local code enforcement officer and/or the local public health officer to inspect/evaluate the problem.

3) Obtain legal advice. Depending on your situation, your local office of Pine Tree Legal Assistance may be able to help you or contact the Maine Lawyer Referral Service to locate an attorney near you.

4) Consider moving. If the mold problem is severe or if you or a member of your household has mold allergies, sensitivities, or chronic lung or immuno-suppressed illness, finding another place to live is a reasonable course of action.

Other Recommended Reading for Your Landlord: Provide your landlord with a copy of the guidance document called: “Read This Before You Turn Over a Unit“. It provides cost-effective tips and strategies for how to prepare safe and healthy rental properties.

Q. I live in a recently built home that has a mold problem. What Can I Do?

A. There are many excellent resources available to builders to address how to build homes to prevent the moisture problems that cause mold. Provide your contractor with a copy of the Maine Indoor Air Quality Council’s Checklist for New Residential Construction view the Building Science Corporation’s article on how relative humidity in your home can lead to mold growth. If you live in a recently constructed home and are experiencing mold and/or moisture problems, talk to your contractor and work with them to explore the source of the excess moisture. Most contractors should be willing to work with you and product manufacturers to address building systems failures.

If it has been a while since the home was constructed, it may no longer be the responsibility of the contractor to address the problem. You can either hire another contractor, or have the building thoroughly inspected by qualified home inspector with experience in diagnosing construction problems.

If your contractor is unwilling to work with you to address the problem and you feel it is their responsibility to do so, you can contact the Maine Department of the Attorney General (207-626-8800) to determine what rights you have under Maine law.

Q. I live in or have living space in a refinished basement. Will I have a mold problem?

A. If your basement has an uninsulated slab (insulation above or below the concrete floor surface) or has uninsulated wall surfaces (either inside or outside the wall) – your basement space is at significant risk of having a mold problem. In Maine, the earth temperature remains cool all year long. Summer heat and humidity levels will cause condensation to form on any uninsulated basement surface that is in contact with the cold earth. This can lead to mold growth on porous materials – wallboard, carpeting, bedding, wood, paper, etc. The best way to prevent mold growth in these uninsulated basement spaces is to use a high-quality, professional-grade dehumidifier. Maintain the humidity level between 30% in the winter and 50% in the summer to prevent mold growth.

Q. My workplace has a mold problem. What can I do?

A. OSHA’s “general duty” clause requires employers to provide a workplace that is free of identified hazards. In order for the general duty clause to be breached, a clearly defined hazard and subsequent exposure must be identified. Because of the inability to set exposure limits/standards, OSHA does not consider the presence of mold as an identified hazard. As a result, OSHA has published various guidance documents for employers (visit the OSHA website) emphasizing the prevention of mold in the workplace. Employers with questions about mold in their workplace can contact the Maine Department of Labor – Safety Works program and seek additional guidance.

Q. I don’t want to clean up the mold problem myself. How do I find a good mold remediation professional?

A. Make sure that ANY contractor you hire is familiar with current best practice guidance on how to remediate mold problems in buildings. Refer to the U.S. EPA’s guidance document on Mold Remediation in Schools and Commercial Buildings – even if the mold problem is in a home. Contractors can seek training and certification in mold investigation and remediation through various certifying agencies. Visit the American Council for Accredited Certifications website for a listing of available certifications. If you are looking for a local contractor, many fire and flood restoration companies also provide mold remediation services. Remember to ask about their certifications and qualifications to do the work and cross-reference their work with the documents contained in the links above.