Measurement techniques

Ecological and environmental factors

When considering any form of biodeterioration, the 3 factors of concern are:

  1. the material; 
  2. the environment; and 
  3. the organism.
Ecology is the very close analysis of the interaction of organisms with one another and with their environment. The environment in which any organism lives will contribute physical, chemical and biological factors that will have a bearing on the settlement, growth and development of the organism.

 

Fungi in general have a very wide temperature tolerance range from 0-60ºC. Relative humidities exceeding 65% are generally required. They have very simple food requirements, being sustained by only small amounts of simple sugar and other organic matter. The nutrient requirements of fungi are satisfied in the built environment by dust and organic deposits. Air movement can provide sufficient oxygen. Only water availability limits the growth of fungi in buildings.

Water availability in buildings depends upon its source and movement, the occurrence of moisture reservoirs and sinks, heating, insulation, ventilation, external conditions, orientation of the building, materials and occupants. These interrelationships are complex and it is difficult to draw conclusive evidence in relation to the moisture availability, growth of fungi and resulting indoor air quality.

The environmental factors affecting the decay of timber are temperature, water, humidity and ventilation.

Fungi differ in their optimum temperature requirements. The optimum temperature for dry rot growth in buildings is about 23ºC; maximum temperatures are about 25ºC and the fungus is rapidly killed above 40ºC. Timber moisture contents of 20-30% in buildings are ideal for dry rot attack and other infestations.

The following environmental and non-environmental parameters are considered most hazardous:

  • relative humidity;
  • ultraviolet light;
  • air temperature;
  • dust;
  • pollution;
  • pests;
  • handling;
  • visitors;
  • fire and water;
  • air movement; and
  • cultural, organisational and management factors.