# Comparison of Methods to Identify and Monitor Mold Damages in Buildings
## 4 Discussion  
### Moisture-Damage Indicator Fungi  
Moisture requirements and substrate preferences of several indicator taxa were compiled in [PERSON] et al. [11], based on a comprehensive dataset (1132 records) of fungi identified in damp buildings in Norway during the years 2001-2006. Despite the limited number of samples in the present survey (48), the dominant indicator fungi and their prevalence in certain materials were, to a large extent, in agreement with previous reports [4; 5; 11; 13]. _Aspergillus_ was the most abundant genus in the mold samples and widely distributed in all the materials, which is not surprising considering its well-known generalist trait [15]. In contrast, some specialist taxa were associated with different substrates: _Acremonium_ with gypsum board, _Chaetomium_ with chipboard, _Stachybotrys_ with gypsum board and wood, and _Trichoderma_ with wood.  
Figure 4: Venn diagrams showing the overlap in distribution of OTUs across sample types (dust and mold). (**a**) Mean percentage of overlapping and unique OTUs (with standard deviations), calculated on an apartment-by-apartment basis for the 11 apartments that included dust samples from both damaged and central rooms; (**b**) the same kind of data as “a” but calculated for the 25 apartments that only include dust from the damaged rooms; (**c**) overall percentages and number of OTUs (in parenthesis) for the same 25 apartments as “b”, without separated calculations by apartment.  
In building ecology, a challenging task is to differentiate between moisture-damage indicator fungi that can colonize building materials, and grow under indoor conditions, from those widespread airborne fungi more related to outdoor air, vegetation, and the household food [13], whose distribution indoors is largely driven by stochastic processes. Previous studies have demonstrated that the indoor dust mycobiota is mainly composed of spores and hyphal fragments coming from both outdoor and indoor sources [22; 23; 35; 36; 37]. Our study has also reflected this dual origin of the dust fungi. Taxa clearly related to the outdoor environment, such as the plant-associated _Thekopson_ and _Fomitopsis_, were found, as well as taxa that can be related to secondary indoor sources: _Saccharomyces_, which is often found in the occupants' skin [23], or _Chaetomium_, _Aspergillus_, and _Serpula_ which can grow and produce millions of spores on different damaged materials [11]. The ecology of the genera _Cludosporium_ and _Saccharomyces_ is very diverse, being widely distributed in both outdoor (e.g., soil and phyllosphere) and indoor environments. However, previous studies on dust have demonstrated that the proportion of _Cludosporium_ is often higher in outdoor samples, while _Saccharomyces_ is higher in indoor samples [22; 23; 35]. These multiple inputs led to a high fungal diversity in the dust samples, which showed a much higher richness than the mold samples. Fungal communities in building areas with visible mold growth are characterized by a limited diversity with a few dominant taxa that are growing on the material surface [24; 25; 26; 38].