Moulds are fungi (like mushrooms) which are present at low levels virtually everywhere, indoors and outdoors.
Moulds need organic materials (eg. leaves, wood paper or dirt) and moisture to grow. Combined with natural humidity, the steam and moisture created by cooking, showering, bathing and washing can result in mould. Mould is often green, grey, brown or black and produces a must smell. It is common in tropical and sub-tropical parts. Moulds release countless tiny, lightweight spores which travel through the air and these spores can be harmful to mould sensitive people.
Moulds can trigger asthma attacks and aggravate other respiratory and allergic conditions. Symptoms depend on the amount of airborne spores a person is exposed to and how sensitive they are to moulds.
Good ventilation in your house helps remove musty smells and mould.