Outdoors, you can find mold growing in places like soil, wood, decaying plants and dead animals.
Some places where mold likes to grow in the home include carpet, paper, clothes, leather, drywall, wood, insulation and food.
More places where mold commonly grows in the home can be found at Where Mold Grows.
Conditions for Mold Growth in Houses
Besides oxygen and organic materials containing carbon to provide nutrients, the other main requirement mold needs to grow is moisture. You can find mold growing almost anywhere provided there is enough of a moisture source for it. Causes of Mold has more information about what causes mold in the home.
Mold problems cannot develop in houses unless there is a moisture problem. The moisture accumulation might be caused through humidity, condensation, or water intrusion from leaks, spills, floods, etc. Most molds only require suitable materials to be wet for 24-48 hours before they can grow.
Molds that can survive using only humidity as their moisture source are called Xerophilic, whereas other molds require an accumulation of moisture to grow. Indoors the best way to prevent mold growing is to limit moisture. To find out more about preventing mold in your home visit Prevent Mold.
Besides moisture, mold also needs the temperature to be right before it can begin to grow. Mold grows best in temperatures that we would consider warm, however there are some mold species that can even grow in temperatures as low as 2 degrees Celsius. If a mold colony's environmental conditions become unfavorable, instead of dying it can lay dormant until conditions become right again when it can continue to grow.
Toxic and/or Black Mold Information
A mold colony is thought of as a single organism. The main body (called mycelium) of a mold colony is made up of a network of connected multicellular filaments called hyphae. Visible mold growth is always in colonies, as mold that is not in a large colony is too small for us to see with the naked eye.
Mold digests what it is growing on using enzymes which are released from the tips of the hyphae and break down the material the mold is living on. The hyphae then absorb these nutrients which can be passed through the mycelium and leads to the mold colony growing.
Mold Spores Information
If conditions such as temperature, oxygen levels, light, and available nutrients are right, the mold may create spores at the ends of the hyphal cells. Mold uses spores to reproduce in the same way that plants use seeds.
Once formed, the spores of mold will begin to be released into the air and spread t0 create new mold colonies. If a 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 mold colony. One of the main environmental requirements for the spore to grow is moisture; to grow into mold, most spores need the surface to be damp for 24-48 hours.
Mold 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.
Out of the several hundred thousand species of molds, there are about 16 different species which are known as toxic molds because they can release mycotoxins which are toxic to humans and animals. Some of the most common toxic molds are:
Not all mold that appears black or dark is toxic or Black-mold. This is why if you find black mold which you suspect is giving you toxic symptoms then you should have it tested to identify the species of the mold before taking any drastic measures such as moving out or getting rid of your belongings. Visit Mold Testing to find out about testing your home for mold.
Why is Toxic or Black-Mold More of a Problem Now?
Toxic or Black-mold 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 mold growth. Also many of the building materials used today are very well suited for mold growth.
The Toxic Black-Mold History page details the history of Stachybotrys, aka toxic black mold.
Toxic Black-Mold Problems & Sick Building Syndrome
Mycotoxins produced from toxic mold is one of the major causes of sick building syndrome. If there is a toxic mold 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.