The National Institutes of Health in the US National Library of Medicine published an article, Associations between Fungal Species and Water-damaged Building Materials, which references information regarding mold growth in water damaged buildings as well as different methods of sampling mold growth.
“Most water damage indoors is due to natural disaster (e.g., flooding) or human error (e.g., disrepair). Water can seep into a building as a result of melting snow, heavy rain, or sewer system overflow. Water vapor can be produced by human activities like cooking, laundering, or showering and then condense on cold surfaces like outer walls, windows, or furniture. Damp or water-damaged building materials are at high risk of fungal growth (mold growth), possibly resulting in health problems for the occupants and the deterioration of the buildings. The water activity (aw) (aw × 100 = % relative humidity at equilibrium) of a building material is the determining factor for fungal growth and varies with the temperature and the type of material (27). The longer a material’s aw is over 0.75, the greater the risk of fungal growth (49), though different fungi have different aw preferences (11). Some filamentous fungi can grow on a material when the aw is as low as 0.78 (26), while others can survive 3 weeks at an aw of 0.45 (30). The severity of indoor dampness varies with the climate, but WHO (52) estimates that in Australia, Europe, India, Japan, and North America, dampness is a problem in 10 to 50% of the buildings, and Sivasubramani et al. (41) estimate that fungal growth is a problem in 15 to 40% of North American and Northern European homes.”
© 2011, American Society for Microbiology