What is Mould?
Unlike plants, moulds do not get their energy from the sun through photosynthesis. In fact, the sun's ultraviolet light inhibits mould growth.
Moulds also digest or "eat" the material they are growing on. The role of mould is to break down decaying organic matter such as dead plants, leaves or dead animals.
Mould Growth Indoors and Outdoors
Outdoors, you can find mould growing in places like soil, wood, decaying plants and dead animals.
Some places where mould likes to grow in the home include carpet, paper, clothes, leather, drywall, wood, insulation and food.
More places where mould commonly grows in the home can be found at Where Mould Grows.
Conditions for Mould Growth in Houses
Besides oxygen and organic materials containing carbon to provide nutrients, the other main requirement mould needs to grow is moisture. You can find mould growing almost anywhere provided there is enough of a moisture source for it. Causes of Mould has more information about what causes mould in the home.
Mould problems cannot develop in houses unless there is a moisture problem. The moisture accumulation might be caused by humidity, condensation, or water intrusion from leaks, spills, floods, etc. Most moulds only require suitable materials to be wet for 24-48 hours before they can grow.
moulds that can survive using only humidity as their moisture source are called Xerophilic, whereas other moulds require an accumulation of moisture to grow. Indoors the best way to prevent mould growth is to limit moisture. To find out more about preventing mould in your home visit Prevent Mould.
Besides moisture, mould also needs the temperature to be right before it can begin to grow. Mould grows best in temperatures that we would consider warm, however, there are some mould species that can even grow in temperatures as low as 2 degrees Celsius. If a mould colony's environmental conditions become unfavourable, instead of dying it can lay dormant until conditions become right again when it can continue to grow.
Mould Biology Information
A mould colony is thought of as a single organism. The main body (called mycelium) of a mould colony is made up of a network of connected multicellular filaments called hyphae. Visible mould growth is always in colonies, as mould that is not in a large colony is too small for us to see with the naked eye.
Mould digests what it is growing on using enzymes which are released from the tips of the hyphae and break down the material the mould is living on. The hyphae then absorb these nutrients which can be passed through the mycelium and leads to the mould colony growing.
Mould Spores Information
If conditions such as temperature, oxygen levels, light, and available nutrients are right, the mould may create spores at the ends of the hyphal cells. Mould uses spores to reproduce in the same way that plants use seeds.
Once formed, the spores of mould will begin to be released into the air and spread to create new mould colonies. If spore lands on a suitable material and other environmental conditions are suitable then the spore can germinate into a new hyphal cell and begin a new mould colony. One of the main environmental requirements for the spore to grow is moisture; to grow into the mould, most spores need the surface to be damp for 24-48 hours.
Mould spores continually float through the air outdoors and indoors and it is impossible to eliminate them all inside buildings. Spores are resilient and even if they do not germinate they can last for years.
What is Toxic Mould?
Out of the several hundred thousand species of moulds, there are about 16 different species which are known as toxic moulds because they can release mycotoxins which are toxic to humans and animals. Some of the most common toxic moulds are:
Aspergillus
Fusarium
Paecilomyces
Penicillium
Stachybotrys
Trichoderma
Not all Black Mould is Toxic Mould
Not all mould that appears black or dark is toxic. This is why if you find black mould which you suspect is giving you toxic symptoms then you should have it tested to identify the species of the mould before taking any drastic measures such as moving out or getting rid of your belongings. Visit Mould Testing to find out about testing your home for mould.
Why is Toxic Mould More of a Problem Now?
Toxic mould species have always existed of course but recently they seem to be more of a problem. One reason is because of new building construction codes which came about during the 1970s in response to the energy crisis. These codes aim for higher conservation of energy which requires new buildings to be more airtight.
This means that buildings are less ventilated, not being able to "breathe" as freely and pockets of moist air can be trapped for long periods of time, potentially leading to mould growth. Also, many of the building materials used today are very well suited for mould growth.
The Toxic Black Mould History page details the history of Stachybotrys, aka toxic black mould.
Toxic Black Mould Problems and Sick Building Syndrome
Mycotoxins produced from toxic mould is one of the major causes of sick building syndrome. If there is a toxic mould infestation in one part of a building the mycotoxins produced from it can quickly spread throughout the building in the air conditioning affecting everyone throughout.
To be followed, part 2 ... Mould symptoms