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What is mold?

Molds are simple, tiny organisms, present almost everywhere, indoors and outdoors. Everyone is exposed to some mold every day without apparent harm. Molds will grow and spread whenever enough moisture is available and organic material is present. If indoor mold contamination is extensive, it can cause large amounts of spores to be present.

Does mold cause health problems?

Molds can produce health effects such as asthma attacks, sinus congestion, eye irritation or skin rashes through swelling, allergy or infection. The amount of mold causing a health problem varies greatly from person to person. There are no legal standards in California for how much mold is too much. If you can see or smell mold inside your home you should find and get rid of the moisture causing the problem. Then cleanup and remove the mold.

What to do about mold if you are a renter

If you are renting your apartment or home, immediately notify your landlord in writing of the mold problem.

If you are a tenant, landlord/tenant laws determine your rights and your landlord´s responsibilities for dealing with mold problems. As of January 1, 2016, visible mold will be considered a substandard housing condition in Health and Safety Code 17920.3, and local enforcement agencies will have clear authority to address mold complaints. Call the Code Enforcement Department of your local jurisdiction for information on how to report a mold problem.

The California Department of Consumer Affairs publishes a booklet summarizing these laws. The booklet also contains a list of resources where to get legal help. Contact them at 1-800-952-5210 or online at

What to do if you are a homeowner

Check with your insurance company to find out if your policy can help pay for dealing with the problem. Consider whether you need to disclose this mold problem when selling your home.

Is testing for mold a good idea?

The California Department of Health Services does not recommend testing as a first step to determine if you have a mold problem. Reliable air sampling for mold can be expensive and requires expertise and equipment that is not available to the general public. There are few available standards for judging what is an acceptable quantity of mold. All locations will have some mold, and how it will affect each person varies greatly. So knowing the amount and type of mold present doesn´t necessarily tell you what you need to know to deal with the problem. As a general rule, if you can see or smell mold, you likely have a problem and should take steps to deal with it.

How to get rid of mold

Find and get rid of the source of moisture that is allowing the mold to grow. If this isn´t done, your mold problem will likely return, and the time and money that was spent cleaning up the mold will have been wasted. The California Department of Public Health fact sheet on mold (in spanish) has web links to lists of cleanup guidelines and consultants, and also tips on how you can clean up a mold problem.

Choosing a contractor

Homeowners or landlords arranging to have mold problems treated need to choose their contractors carefully. There are no specific California contractor guidelines, regulations or licensing for dealing with mold problems.

For more Assistance

If you still need assistance after reading this fact sheet, contact the Contra Costa County Hazardous Materials Ombudsman at 925-250-3227. For information about other health and hazardous materials issues, visit or call 1-888-959-9911 or 211.

Information in this fact sheet is based on material provided by the California Department of Health Services.