Mold Facts and Myths
There are a lot of half-truths and outright lies floating around, held as truths by most people. It's hard to know what's what, especially when the phrase "black mold" starts getting thrown around. This is a collection of those myths, together with the actual information, in the hopes of putting some of these to rest. You may also be interested to read Frequently Asked Mould Questions.
Myths
Myth #1: There is only one type of black mold, and it's very bad.
Fact: In actuality, there are a lot of moulds that look black. The type of black mould that made the news years ago, associated with a lot of ill health effects, was called Stachybotrys (pronounced 'stack-ee-bot-riss'). However, there are a ton of other molds that look black, and are fairly common and generally not of concern. The take-home message here is that not all black molds are 'bad'.
Myth #2: Only black molds are bad. Other types shouldn't be worried about.
Fact: A lot of people aren't even aware that mold can be white, or orange, or blue, for instance. The colour of a mold generally has to do with the spores it produces, and has no bearing on whether it is dangerous or not. There are some white molds that grow on walls and other surfaces that can be just as bad as some harmful black molds.
Myth #3: If I see mold, I should just scrub it with bleach to get rid of it.
This is a complicated myth. There are a couple of different parts to it.
Bleach: Bleach is generally not recommended as a fungicide (mold killer). It works by dousing the mold in toxic levels of a chemical. The problem is twofold: not only are humans just as susceptible to bleach's damaging properties, but the bleach is generally a water-based solution. In the long run, this often means that water penetrates the surface, giving moisture to the roots of the mold, which happily begins to grow again. In the case of small patches of mold, ordinary household detergent will suffice. It is important to make sure that the area dries quickly (ideally within 24-48 hours) so that any small bits (too small to see with the naked eye) of mold left over don't get the chance to start growing again.
Is it really gone? Mold is able to grow because it has a moisture source. Often this means that there is or was a leak or something similar involved in the first place. Just removing the mold without fixing the water problem will usually result in the mold coming back. Also, mold can grow behind walls in addition to just on them, so it is important to determine whether you've only dealt with a portion of the mold, or the whole thing.
Myth #4: I can just paint over the mold to seal it up.
Fact: Actually, mold can eat the paint. Many people attempt to paint over mold only to discover that in a few months the mold has either poked its way through the paint, or the paint has started peeling off. The mold really has to be removed before painting can be done, even if you're using "mold-resistant" paint.
Myth #5: Mold and mildew are totally different things.
Fact: Mildew is mold. It's a word that is used generally to refer to a few specific types of molds, but it's still all mold.
Mold Facts
And now, a few facts to round out the discussion:
Fact #1: Mold is everywhere, no matter what you do.
Bits of mold are part of the air you breathe everywhere you go. Molds grow on plants and in soil, float off into the air, and float in through your doors and windows. You've been dealing with it all your life and there is usually no way (except in very special circumstances) to create a space with no mould in the air.
Fact #2: Large areas of mold should really be dealt with by a professional.
When mold areas get larger than about 10 square feet (about a square meter) or you don't know the extent of the problem (for instance: mold can grow behind the walls) it is important to bring in a professional who is familiar with how to deal with mold properly. This sized area usually requires extra precautions when removing mold. Much larger areas of mold can require very complicated procedures and precautions. Even a common, usually harmless mold can be a health issue when there is a lot of it. (For those interested in knowing the specifics, here is some documentation on the Canadian and American mold removal guidelines.)
Fact #3: Stains and mysterious spots are not always mold.
Sometimes a black, brown, grey, or white spot isn't actually mold. Effluorescence, for instance, is a whitish deposit, especially on concrete, that happens when water permeates the material and leaves behind a deposit of salts. Note, however, that in this case there is water permeation, which may mean there is mold growing where you don't see it. Other spots can be caused by soot or soil deposits, giving a darker colour. If you want to know what you're looking at, you can collect samples yourselves and send them to mold laboratories that can test air samples or pieces of material and tell you whether you have mold or not.