## 3 Results and Discussion
This,  
Figure 4: Time needed to reach definite mould growth stage for 'Dry’ and 'Wet’ specimens at different conditions: (**a**) mould germination and (**b**) visible mould growth. as mentioned above, could be due to competition between different mould species in the case of the VTT model, which inhibits mould development [38]. The results of the 'Dry' specimens are similar to the ones exposed to the mould contamination at 30 \({}^{\circ}\)C. However, they are completely different at 20 \({}^{\circ}\)C, suggesting that initial spore concentration is very important under these conditions. Taking into consideration that the detection of mould growth in the early development stages can be difficult, and therefore, it is not always known if the indoor air is actually 'clean' from the spore contaminators [56], the results suggest that the VTT model is safe and reliable for mould prediction on wood. The results of other frequently used methods (Sedlbauer isopleths, WUFI-Bio model, etc. ), which are summarised in the paper by [PERSON] and [PERSON] (2012), differ considerably from the presented results [57]. At RH 97% and temperature 20 \({}^{\circ}\)C, most of these models predict much sooner mould germination (\(\sim\)5 to 10 times) than we have observed in our experiments. On the other hand, WUFI-Bio model predicts longer period (\(\sim\)2 times), which is more comparable to the results of the 'clean' conditions. In general, much more research would be required to ascertain which one of the models is more reliable. However, based on our experiments and the covered environmental conditions, a relatively precise and safe model that could potentially be used for development of indicative warning system for potential risk of mould growth at extreme situations (RH > 90% and temperature > 20 \({}^{\circ}\)C) indoors for wood is the VTT model. Effect of the MC of Wood on Mould Growth Development Exposed to Environment with Mould Contaminator (Experiment IV)  
The effect of the MC of wood on mould development was evaluated in the experiment in which 'Dry' and 'At EMC' specimens were exposed to an environment favourable for mould growth. A significant difference was observed for the 'At EMC' rate, reaching EMC between the RH of the environment while no effect of temperature was detected. Although there were significantly greater changes in MC for the 'Dry' specimens exposed to an environment of RH 97% than for their counterparts at RH 91% (increases of 15% and 10%, respectively), similar time was needed for them to reach EMC (Figure 6). This agrees with the finding that the rate of absorption for a smaller RH increment was slower than for a larger RH increment [58]. Figure 5: Influence of mould contamination on the time necessary reach (**a**) mould germination and (**b**) visible mould growth stages; 'Dry’—no contamination, ’Dry (with contaminator)’—with mould-infected object, VTT model—prediction by VTT model (spore suspension) [24]: light blue dots on the T and RH plane are the corresponding projections of the results. Some effect of wood MC on mould development was only observed for the specimens exposed to an environment of RH 91% and a temperature 20 \({}^{\circ}\)C when significantly less time was needed for mould germination on the 'At EMC' specimens (Figure 7). These specimens were detected reaching the visible mould growth stage more rapidly compared with their 'Dry' counterparts. However, the difference in the time to reach visible mould growth between the 'Dry' and 'At EMC' specimens was not significant (\(p>0.05\)) for any of the environmental conditions. These results suggest that the wood MC is not of significant importance for mould development, at least under the studied conditions of high RH. The findings agree with the other studies [15; 16].