1 - All moulds are dangerous when they are in large enough quantities. Some people are more susceptible to mould and will react at lower quantities. But everybody can be affected.
You will hear people talk about dangerous moulds and Non dangerous moulds. This is a misrepresentation of the problem. Mould is dangerous when you are exposed to high concentration levels. This applies to all moulds.
When you hear someone talk about black mould being the most dangerous, what they actually mean is that black mould requires less concentration to be harmful to the human body.
What we typically see in households is one or more of these moulds having an out break in the home.
This can be for a variety of reasons e.g broken pipe, bad weather conditions, poor house constructions honestly the list could go on forever. What is important is that you can get rid of these mould and other moulds and bacteria if you use the right prevention method.
The important aspect to note with mould is that mould works slowly for the most part. By the time you notice mould in your house you have most likely already had it for months.
You will not notice you health deteriorating quickly what you might notice is that one day you will say "Why am I always sick all the time.". If you notice you are always sick or have mysterious illnesses you should look at preforming a mould inspection or testing your self to see if you are living in a mouldy house.