Is all mould (mold) harmful to humans?

No.  We share the planet with literally hundreds of thousands of kinds of mould, also known as mildew or fungi.  Most are harmless to us.  Some, like mushrooms, we eat.  The organisms that are known to be harmful to us include Stachybotrys atra, Aspergillus versicolor, Penicillium chrysogenum, and Alternaria.  Sampling and laboratory testing can determine the type if concerned.

I have heard that Stachybotrys is the dangerous "killer" mould.  What is it?

Stachybotrys atra is a greenish-black fungus that can grow on materials with a high cellulose and low nitrogen content such as fibreboard, gypsum board, dust, and lint if it becomes moist due to excessive humidity, leaks, condensation, or flooding.  It can produce several toxic chemicals called trichothecene mycotoxins.  These mycotoxins are known to be toxic to humans exposed to significant quantities.  People who handle contaminated materials have developed dermatitis, blood and immune systems disorders.  When Stachybotrys atra spores are inhaled by humans, they have developed allergic, respiratory and immunologic symptoms as well as asthma, hypersensitivity pheumonitis, allergic rhinitis, dermatitis, sinusitis, and conjunctivitis.  Other symptoms include fatigue and an inability to concentrate.  There have also been reports of people experiencing cold and flu symptoms, diarrhoea, headaches, rashes, and other respiratory symptoms when they were exposed to Stachybotrys atra.

I can see what looks like black mould growing in my child's classroom.
Is it Stachybotrys?

All moulds can appear black.  So the fact that it is black does not necessarily mean that it is Stachybotrys.  However, we should not have moulds of any type growing in our schools, workplaces or homes.  You should ask to have it identified.

What are the clues that it might be Stachybotrys?

If the material it is growing on has been persistently wet, and especially if it is cellulous, it may be this fungus.  If the material is wet to touch, and has been that way for some time, chances are good that it may be Stachybotrys.  A sample taken to a laboratory would confirm the type.

We have a report that shows the air to be "acceptable", but Stachybotrys was identified as growing on surfaces and behind wall coverings.  Is it O.K.?

The Stachybotrys spore is heavy and falls out of the air quickly.  It is very rare that you will find this organism with today's sampling methods.  In the case of Stachybotrys, it is the toxin it produces that is of concern.  Thus far, the toxin has been difficult if not impossible to detect.