Samples of dust collected from carpeting can provide an indication of the microbial condition of a building with the carpet material having potential to be both an amplifier (growth site) and reservoir for fungi. Interpretation of the data obtained from analysis of the dust is helpful when making a determination as to the overall condition of both the building and the carpet material. The authors have collated data from 243 samples collected in both problem and control buildings across the USA. A comparison is made between the results obtained from both problem and control buildings, with particular emphasis on the biodiversity found and the regional differences observed. The study concludes that despite the ubiquitous nature of fungi there are a number of key indicators which can be used to determine if the dust from a carpet suggests a contaminated building.