Microbial Risk Indoors

Five factors affecting fungal growth.

Temperature

• Mesophilic organisms commonly found in water-damaged environments thrive at moderate temperatures, approximately 20°C to 45°C.
• Moulds are highly adaptable and can grow across a wide temperature range.
• They can grow in both cold environments, such as on food in refrigerators, and in dry climates.

Light

• The belief that mould only grows in dark environments is a myth.
• Mould often thrives in the dark due to higher relative humidity or greater moisture availability.
• Light exposure can trigger moulds to release spores, as it reduces the moisture available to them.

pH

• Mould prefers a slightly acidic environment, slightly less than pH 7.
• pH requirements may differ between organisms.

Nutrients

• Cellulose is a preferred nutrient source for mould.
• Moulds secrete enzymes that break down and liquefy cellulose-containing materials.
• This process releases cellulose, which moulds absorb through their membranes.
• Over time, moulds not only feed on these materials but weaken their structural integrity.

Water activity

• Free water is the most critical factor for microbial growth.
• Different microorganisms require varying levels of moisture to grow.
• Fungi are heterotrophs and saprophytes, meaning they rely on external organic food sources, especially those rich in cellulose.
• Moulds can grow on any surface that holds organic residue, such as dirt, soil or a biofilm.