Myth #1: Mould that come back after treatment with bleach is is mould that is more than one year old.

The Truth: Bleach may not be 100% effective against all moulds. Mould will grow as long as there is moisture, nutrients and suitable temperature for growth. Growth may start from just a few spores or hyphal fragments that escaped bleach or were not killed by bleach. To control mould, one needs to keep the house or building dry. This means the moisture source or causes need to be identified and fixed. The other truth about mould is that there is currently no way of telling how old the mould is and whether it was there one year or two years ago. Spores of some moulds can remain viable on surfaces of building material for several years until they get the right conditions for growth.

Myth #2: Black mould is deadly.

The Truth: All moulds are potentially harmful regardless of their colour. However, not all black moulds are known to cause health problems. Some black moulds that could be of health concern are Aspergillus niger and Stachybotrys chartarum (greenish black). Aspergillus flavus is not black and it is the most well known producer of the potent mycotoxins called aflatoxins. Aspergillus fumigatus is also not black and is one of the biggest concerns in hospitals because it can infect people particularly those with low immunity.