Mold is a fungus that reproduces by creating small spores that work like seeds. Every home has mold. Mold spores can be unwelcome guests floating in on the breeze through an open window or door, hitching a ride on clothing or hiding in plain sight on packaging materials like cardboard or paper. Once established, it will look like fuzzy spots or blotches that can be black, green, brown, yellow, and even orange or white.
There are nearly 1,000 types of household mold. A few common culprits are Alternaria, Aspergillus, Cladosporium and Penicillium. The dreaded black or toxic mold that you see in the headlines, Stachybotrys chartarum, also know as Stachybotrys atra, isn't a common mold, but it's not rare either. It will look dark green or black.
You can't keep mold out, but you can make it less welcome. Household mold needs hospitable conditions in which to thrive. One key ingredient in establishing and maintaining a mold colony is moisture. If you don't have a consistent source of moisture, mold won't be able to survive. [source: Consumer Reports]
This sounds pretty simple. All you have to do is keep the inside of your house dry, and you won't get mold. But keeping moisture out is harder than it may seem. There are the obvious sources of moisture you can watch out for, like leaks in the plumbing and the roof, but there are other ways moisture can get in that are harder to control. Steam from cooking and bathing can create conditions that will encourage mold, and condensation can be a big problem too. Warm air has the capacity to hold more moisture than cooler air. As this moisture-laden air starts to cool down, such as near the windows in summertime, it deposits water in the form of condensation. Condensation can accumulate on the insides of windowpanes and on pipes and walls, creating a great environment for mold, sometimes in spots you wouldn't expect. Mold is an equal-opportunity fungus. It can live in your walls, on wood, furniture and carpeting or on hard surfaces like tile, glass and metal -- practically anywhere.
In the next section, we'll take a look at ways to check for mold.