What is Mould?
What is mould? and where does it come from?
Mould is a type of fungus. It grows on surfaces in masses of branching threads which resemble dense cobwebs. The fertile threads, those which produce spores, often stand up from the surface into the air to release their spores. Spores are carried by air currents or by adhering to insects or animals. Active mould can be any colour, depending on the species and the substrate upon which it is growing. Mildew is another type of fungus, similar in structure to mould, but distinct as one species of fungus is distinct from another. The terms “mildew” and “mould” are not interchangeable; they are most often used in the common names of various fungi. Fungi is a kingdom of organisms, with a single division, Mycota. The fungi have traditionally been classified with plants but are now considered a distinct group of organisms.
Health problems
Mould & Health Problems
Mould and mildew can have an adverse effect on people. Those with allergies, asthma or other respiratory problems should stay away from infested areas, as many fungi will seriously irritate and inflame lungs. Some fungi can cause skin and eye irritation and infections. Prolonged exposure to germinating moulds in closed areas can damage the lungs, mucous membrane, cornea, respiratory tract, stomach, intestines, and skin. Some varieties of mould are highly toxic.
What is a Mould-Preventive Environment?
There are a number of factors which influence the growth of mould: environmental humidity and moisture content of materials, temperature, air circulation, light, and the chemical composition of potential substrates.
Humidity. The most important environmental factor to control is the amount of moisture in the air. Some moulds can begin growing at 70% relative humidity or higher and then continue growing at relative humidity of less than 70%.
Temperature. Most moulds thrive at warmer temperatures. When combined with high levels of humidity, temperatures of 70 to 75° Fahrenheit can cause mould to develop. Temperatures below freezing will not kill mould, but they do make it dormant. Few moulds will be active at temperatures of less than 50° Fahrenheit. Mould can also grow in conditions up to 140° Fahrenheit.
Air Circulation. In conjunction with humidity and temperature control, adequate air circulation will help prevent mould growth. Air circulation helps control moisture levels through evaporation.
Installing a heating/ventilation/air conditioning system with humidity control can solve all three problems of humidity, temperature, and air circulation at the same time. Air Circulation Systems are expensive, not easy to install or simple to maintain.
Not only do suitable systems assist in mould prevention, but they also stabilise the environment and hence eliminate the distortion of materials due to fluctuating temperature and humidity. Furthermore, maintenance of a stable environment slows down processes of deterioration caused by acid, light, and pollution. Fans can be installed to improve air circulation. They are best placed near outside walls and close to floor level. Portable dehumidifiers can be used, particularly for localised problems. Although you can invest in several units, portable dehumidifiers tend not to be as effective in large spaces as a centralised systems with humidity control. Fans and vents in attics will increase air circulation by pulling air through the building. This is particularly useful when it is necessary to leave windows open. Desiccants (such as silica gel) can be used to absorb moisture in humid environments. They should not, however, be used where young children are able to reach them because ingestion may be dangerous. Desiccants are most useful for localised problems, especially those that can be contained in a small, enclosed space.
Light. Sunlight, and in particular ultraviolet radiation, generally inhibits mould growth. It was found that more light correlated with slower growth rates.
Unlike plants, which produce their own food, fungi absorb nutrients from dead or living organic matter. Fungi also lack photosynthetic pigments. There are over 100,000 known living species of fungus, some of which are beneficial to mankind. Mycologists estimate that there may be as many as 200,000 more unidentified species of fungus. Yeast’s, moulds, mildews, rusts, and mushrooms are types of fungus.
The spores of fungi that become mould or mildew are always present in the air and on objects. When the temperature and moisture in the environment are suitable for germination, the fungus spore bursts and grows into a threadlike filament called a hyphae. Using the object it is growing on as a food source, the hyphae form a mass, called a mycelium, and within a short time begin to produce spores. At maturity, spore sacs burst and release spores, which eventually land on other material and begin the reproductive cycle again.
Optimum conditions for mould and mildew development exist when temperature is above 70° Fahrenheit and relative humidity is above 70%. However, some common moulds can grow at temperatures as low as 50° Fahrenheit and in relative humidifies as low as 45%. It is also possible for moulds to begin growing in conditions of high relative humidity and temperature and then continue growing in environments with significantly lower relative humidity and temperature.