These biological agents can arise from a host of means, but there are two common classes:
(a) moisture induced growth of mould colonies
and
(b) natural substances released into the air such as animal dander and plant pollen.
Moisture build-up inside buildings may arise from water penetrating compromised areas of the building envelope, from plumbing leaks , or from ground moisture penetrating a building foundation. Especially in the absence of light and with a lack of air circulation, mould colonies can propagate and release mycotoxins into the air. In a situation where there is visible mould and the indoor air quality may have been compromised , a mould inspection and/or mould remediation may be needed.
Through an inspection one should be able to determine the presence or absence of mould, which can cause allergic reactions and /or affect the respiratory system; there are some varieties of mould that are toxic in nature. Indoors, mould growth can be inhibited by keeping humidity levels below fifty percent and by eliminating leaks or moisture condensation and accumulation
Conditions for mould growth
Moulds are part of the fungi kingdom and serve an important role in breaking down organic matter. They are found both indoors and outdoors. Fungi can form a colony, which is a visible mass of interwoven filaments that may appear cottony, velvety, granular, or leathery. Fungi can be any colour but usually will appear as a shade of white, grey, brown, yellow, or green. The fungi most commonly found growing indoors are often called “moulds” (for example, species of Penicillium, Aspergillus, and Cladosporium). For the purposes of this document, the terms “mould,” “mildew,” and “fungus or fungi” are interchangeable.
Moulds spread naturally through the release of spores into the air. Any air movement will cause the dry spores to be carried with the air current; eventually the spores will land on a surface. Moulds may also spread through direct mechanical transfer of mould-covered materials, or by a person or animal brushing against a mould and then depositing some mould on another surface. Once a colony of mould is established and subsequently disturbed or damaged, spores may become airborne and spread throughout the building.
As long as moisture and nutrients are present, mould growth will usually continue unabated. Moulds are likely to grow where there is water or prolonged dampness such as water damaged walls, bathrooms, basements, ceiling/roofing material, and damp parts of refrigeration or air conditioning systems (for example, air chillers or drip trays). A source of nutrients for mould is basically any organic material and can include simple sugars and starches as well as more complex carbon containing substances such as paper and wood. Many porous building materials such as some types of insulation, drywall, wallboard, wallpaper, ceiling tiles, and wood contain organic material.
Without moisture, mould cannot grow or reproduce and will enter a dormant stage. In the case of some moulds this dormant stage can last for years. However, given the right conditions, such as water or moisture supply, the mould can become active, start growing again, and release spores.
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