## 3 Results and Discussion
### Monitoring of Airborne Asbestos Fibers  
The air concentrations of the released asbestos particles from the AC composite structures into the indoor air during demolition of the construction elements in the selected building at seven work posts corresponding to floor sampling sites were assessed by the mean values of the number concentrations of fibers before (BR), during (DR), and after removal (AR) of the materials containing asbestos. In Figure 7, the mean number concentrations of asbestos occurring in the working indoor air are given. The low mean values of number concentrations of asbestos fibers in the buildings before ACP removal were observed. They ranged from 111 to 257 m\({}^{-3}\) and no sample exceeded the exposure limit of 1000 m\({}^{-3}\). The values obtained during the removal of ACM significantly depended on the work site and time of sampling. The measurements carried out at the work posts during the asbestos-cement materials removal showed the mean number concentrations of asbestos fiber ranged from 318 up to 2063 m\({}^{-3}\). The differences in these measured values are probably related to the amount of AC materials removed at a given sampling site in the building. The absolute highest mean fibers concentrations were recorded at the sampling site located in the middle part of the building's floor (sample C2). This is consistent with the statement that the highest asbestos fiber concentration exceeded the hygiene \begin{table}
\begin{tabular}{c c c c} \hline
**hkl** & **d** & **2\(\Theta\)** & **Intensity** \\ \hline  & 7.70681 & 11.473 & 11 \\
002 & 7.32795 & 12.068 & 100 \\
020 & 4.52638 & 19.597 & 16 \\
004 & 3.64902 & 24.373 & 71 \\  & 2.74175 & 32.634 & 6 \\
131 & 2.60217 & 34.438 & 9 \\ \(-\)202 & 2.53238 & 35.418 & 6 \\
202 & 2.45262 & 36.610 & 16 \\
204 & 2.09669 & 43.109 & 6 \\
060 & 1.53239 & 60.355 & 12 \\
247 & 1.31305 & 71.839 & 6 \\ \hline \end{tabular}
\end{table} 
Table 4: d\({}_{\rm hkl}\)-spacing of clinochrysotile. Figure 6: X-ray diffraction (XRD) pattern of AC waste sample. standard at the sampling sites inside buildings [15]. The exposure limit of 1000 m\({}^{-3}\) was exceeded only at four sampling posts (B2; B3; C1; C2) during ACM removal. The permissible exposure limit for mineral fibrous solid aerosols like asbestos in a working environment is 0.1 cm\({}^{-3}\) (1.105 m\({}^{-3}\)). On the basis of this limiting value, all the determined number concentrations do not pose any health risk. The lower concentrations were measured two days after removal in the morning (108-295 m\({}^{-3}\)). These obtained values of fibers concentrations are similar to the concentrations measured outside the building (i.e., 104-218 m\({}^{-3}\)). The measured air pollution levels by asbestos fibers are in accordance with the occurrence of fibers published in [18]. The mass concentrations of dust in the studied work posts were also determined. In Figure 8, the mean values of mass concentrations of asbestos dust are presented. Although demolition activities were performed under controlled conditions the fibrous dust was present in the indoor air and its mass concentration values ranged from 0.077 to 2.64 mg/m\({}^{3}\). According to [46], the permissible exposure mass limit for the respirable fraction of asbestos dust in the air was not established. For solid aerosols with possible fibrogenic effects, the highest exposure limit in the air of a working environment is in the range of 0.3 to 6 mg/m\({}^{3}\) (for amorphous silica, it was set at 0.3 mg/m\({}^{3}\) and 4 mg/m\({}^{3}\) depending on the process of dust formation). Figure 8: Mean values of mass concentrations of asbestos dust on the work posts in the building before, during, and after removal of ACPs. Figure 7: Mean number concentrations of asbestos on the sampling sites in the building before, during, and after removal of ACPs.