# Identification of Emission Source Using a Micro Sampler Carried by a Drone
## 5 Conclusions  
Detectors and samplers must be light and low-cost for their successful use on mini drones to monitor pollution in industrial areas [32]. In this work, a telescoping shaft extended an NTS beyond the air turbulence zone, and the sampling device was carried by a DJI Mavic Pro quadrotor drone to identify emission sources of VOCs. A mini drone with an NTS was successfully used to sample air pollutants and identify sources of industrial emissions. The lightness (20 g) and smallness (7 cm long) of an NTS enable its installation as a micro passive sampler on a mini drone that cruises between factories in a highly industrialized zone. Figure 6 shows the DJI Mavic Pro quadcopter as it hovers and samples inside an industrial plant with densely arranged equipment and pipelines, \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{3}{*}{**VOCs**} & \multicolumn{5}{c}{**Concentrations (ppm) at Different Sampling Points a**} \\ \cline{2-6}  & \multicolumn{2}{c}{**RTO Exhaust**} & \multicolumn{2}{c}{**Community (Near Boundary Wall)**} & **Community (in** \\  & **Chimney** & **Point b\({}_{1}\) (@ 65 m) c** & **Point b\({}_{2}\) (@ 20 m) c** & **Point b\({}_{3}\) (Ground) d** & **a Park)** \\  & **Point c (Ground) d** & **Point c (Ground) d** & **Point c (Ground) d** \\ \hline Methanol & 1.96–2.00 & \textless{}0.18 & \textless{}0.18 & \textless{}0.15 & \textless{}0.15 \\ Acetone & 0.05–0.10 & \textless{}0.01 & \textless{}0.01 & \textless{}0.022 & \textless{}0.022 \\ Benzene & \textless{}0.005 & \textless{}0.005 & \textless{}0.005 & 0.13–0.24 & \textless{}0.008 \\ Toluene & 1.04–2.00 & \textless{}0.005 & \textless{}0.005 & 0.20–0.35 & \textless{}0.008 \\ \hline \end{tabular}  
Notes: a Two air samples were collected for each sampling point. Values of concentrations are displayed as the analyzed ranges, and no detections of specific compounds are presented in lower than the method detection limits (MLD). b Air samples were collected by active sampling using Teflon bags, which were connected to an air pump. \({}^{\text{c}}\) Air samples were collected by active sampling using NTS with an air pump, which were carried on a drone. \({}^{\text{d}}\) Air samples were collected by passive sampling using an NTS, which were fixed on the pillar of a road sign.  
\end{table} 
Table 2: Concentrations of VOCs at the specific sampling points at Site B.  
which present obstacles for the flight of large multi-rotors. The low take-off weight of a mini drone limits the lithium battery to supporting a sampling time of no more than 12 min. Owing to the limited flight time of a mini drone, the novel micro sampler can be used to extract representative pollutants for analysis to identify sources of industrial emissions. Notably, the NTS is an environmentally friendly sampler because it is reusable, and thermal desorption in the injection port of a GC-MS system for analysis requires no solvent. Therefore, a drone that carries an NTS is promoted to collect samples of air that is emitted from industrial sources. Even though an NTS has been regarded as an ultra-trace organic pollutant sampler, a sampler which is packed with adsorbents of very high capture efficiencies will be developed in the future. **Supplementary Materials:** The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/drones6050116/s1](https://www.mdpi.com/article/10.3390/drones6050116/s1)]([https://www.mdpi.com/article/10.3390/drones6050116/s1](https://www.mdpi.com/article/10.3390/drones6050116/s1)), Calculation: Use Equation (2) for VOC Quantitative Analysis. **Author Contributions:** Conceptualization, W.-H.C. and C.-S.Y. ; Methodology, W.-H.C.; Experimental Analysis, W.-H.C.; Resources, C.-S.Y. ; Writing, W.-H.C.; Supervision, W.-H.C.; Project Administration, W.-H.C.; Funding Acquisition, W.-H.C. All authors have read and agreed to the published version of the manuscript. **Funding:** The APC was funded by Ministry of Science and Technology, Taiwan, under the funding number MOST 110-2221-E-242-001.