The general rule is this: Anytime mold is found, get rid of it and correct the conditions that caused it. Those conducive conditions are, almost always, excess moisture and a lack of ventilation. Knowing these facts, we should all understand that reducing the moisture in the home is important. Where I live, Washington State, the experts suggest that relative humidity inside the house should be kept between 30% and 50%. To test your home, to see how it fares, you can buy a simple hygrometer or relative humidity gauge. These are easy to obtain online or at the local Radio Shack.
The sources of moisture found in the home include any plumbing leaks, window or roof leaks, steam from baths and doing dishes.
Another source, we seldom think about, is respiration - people and pets breathing. To offset moisture, it is important to keep the house well ventilated. This can be as simple as opening the windows for a few minutes every day or, more complex, running exhaust fans or whole house ventilation systems.
So, if your home develops mold, what do you do about it? In many circumstances, cleanup can be done by the homeowner. Mold loves sheetrock so often remediation involves cutting out the sheetrock and replacing it. Obviously this only works if the source of the moisture has been dried up. Also, before you begin, do some reading on cleaning up mold and wear a respirator. What is toxic to one person might not be to another and vice versa. Molds produce airborne mytoxins. The two molds that have the worst reputations are stachybotrys and chaetomium. These molds, and it is controversial as to just how dangerous they really are, have been accused of creating human diseases from cancer and heart problems to arthritis and bleeding lungs. When dealing with mold, use common sense: Keep relative humidity levels low and make sure the plumbing pipes and the roof do not leak. This is a very complex topic but I am hoping that some of this elementary information will be helpful to other realtors and their clients.