## 3 Results
### Particle Size Distribution Results  
Figure 4 shows the particle normalized number-sized distribution (dN/dlogDp) and surface area concentration (dS/dlogDp) of airborne PM that was generated during the oak wood sanding process. According to [PERSON] and [PERSON] [32], the normalized concentration is the total number, surface or mass concentration (dN, dS or dM) within the measured range divided by the difference between the logarithms (dlogDp) of the lower and upper diameter of the counted particles. This makes the normalized concentration independent of the channel width of the instrument, thus results from instruments with different channel \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Instrument**} & **Sanding** & \multirow{2}{*}{**N**} & **Min.** & **Max.** & **Mean \(\pm\) SD** & **MD** & **Median Diameter** & **GMD \(\pm\) GSD \({}^{\star}\)** \\ \cline{4-7}  & & & **[\#/cm\({}^{3}\)]** & **[\#/cm\({}^{3}\)]** & **[\#/cm\({}^{3}\)]** & **[nm]** & **[nm]** & **[nm]** \\ \hline \multirow{3}{*}{NanoScan SMPS} & P60 & 10 & 3982 & 28,971 & 16,201 \(\pm\) 5985 & 45.63 & 31.69 & 34.03 \(\pm\) 2.08 \\  & P120 & 10 & 4341 & 28,832 & 17,618 \(\pm\) 5987 & 40.33 & 26.02 & 29.32 \(\pm\) 2.08 \\  & P240 & 10 & 4672 & 32,215 & 21,410 \(\pm\) 3898 & 34.59 & 22.94 & 25.80 \(\pm\) 1.97 \\ \hline \multirow{3}{*}{OPS} & P60 & 10 & 29 & 426 & \(191\pm 110\) & \(1.17\times 10^{3}\) & \(0.61\times 10^{3}\) & \(0.79\pm 2.21\times 10^{3}\) \\  & P120 & 10 & 70 & 421 & \(225\pm 97\) & \(1.20\times 10^{3}\) & \(0.64\times 10^{3}\) & \(0.82\pm 2.23\times 10^{3}\) \\ \cline{1-1}  & P240 & 10 & 127 & 504 & \(327\pm 93\) & \(1.30\times 10^{3}\) & \(0.72\times 10^{3}\) & \(0.89\pm 2.26\times 10^{3}\) \\ \hline \hline \end{tabular} Note. * geometric standard deviation.  
\end{table} 
Table 1: Descriptive statistics of measured data by NanoScan SMPS and OPS. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Instrument**} & **One-Way ANOVA and** & **HSD** & **Q \({}^{\star}\)** \\ \cline{3-4}  & **Post-Hoc Tukey’s Test** & **HSD\({}_{0.05}\) = 1487.09** & **Q\({}_{0.05}\) = 3.33** \\ \hline \multirow{3}{*}{NanoScan SMPS} & P60 vs. P120 & 1417.28 & 3.17 (\(p=0.07\)) \\  & P60 vs. P240 & 5208.77 & 11.65 (\(p<0.001\)) \\  & P120 vs. P240 & 3791.49 & 8.48 (\(p<0.001\)) \\ \hline \hline \multirow{3}{*}{OPS} & P60 vs. P120 & 33.36 & 3.98 (\(p=0.01\)) \\  & P60 vs. P240 & 135.94 & 16.22 (\(p<0.001\)) \\ \cline{1-1}  & P120 vs. P240 & 102.58 & 12.24 (\(p<0.001\)) \\ \hline \hline \end{tabular} Note. * studentized range.  
\end{table} 
Table 2: One-way ANOVA and post-hoc Tukey’s test results comparing sanding paper grit by particle number concentration. widths are mutually comparable. Data showed in Figure 4 were calculated as the arithmetic mean from each treatment. During the monitoring of the background number concentration of UFP before the sanding of the oak planks, the shape of a typical Gaussian curve was observed. Thus, particles with diameter approximately from 75 to 100 nm were dominant in the air. In the case of CFP, a clear peak was detectable even before the start of sanding, at a size bin from 0.300 to 0.374 \(\upmu\)m. Immediately after the start of sanding, the particle distribution in the test room was rearranged. As seen in Figure 4, the concentration patterns differed between the investigated sanding paper grits in terms of normalized number concentration as well as LDSA, similarly, size distribution of particles showed the same trend. Apparent peaks of UFP and CFP number concentrations were regularly found at size bin in the range of 13.3 to 17.8 nm, and 0.897 to 1.117 \(\upmu\)m, respectively. However, the maximum values of CFP remained at the level of 0.3 \(\upmu\)m, with a subsequent sharp decrease. Interestingly, UFP in size bin midpoints from 64.9 to 154.0 were generated in higher number concentrations during P60 and P120 grits performance, compared with sanding paper with grit P240.