Housing Program: Mold Information

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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.

Common sources of moisture that may lead to indoor mold problems include:

  • Flooding
  • Leaky roof
  • Sprinkler spray hitting a building
  • Plumbing leaks
  • Overflow from sinks or sewers
  • Damp basement or crawl space
  • Steam from showers or cooking
  • Humidifiers
  • Wet clothes hung to dry indoors
  • A clothes dryer that exhausts air indoors

Prevention is important to avoid mold problems. Inspect your home, school, or workplace regularly for signs and sources of indoor moisture and mold.

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 clean up and remove the mold properly.

What to do about mold if you are a renter

Visible mold is covered by the California Housing Code: visible residential mold at a level that may be hazardous to occupants is a condition that makes housing substandard. The visible mold can be cited by local code enforcement so that the owner is required to remediate the problem. Often the challenge for the renter, when the owner is unresponsive to requests to fix the problem, is to identify the proper code enforcement authority to enforce the California Housing Code.

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 general public. There are a 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 webpage on mold provides a list of clean-up guidelines and consultants, and also information on how you can clean up a mold problem.


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