<https://www.gdscorp.com/blog/voc-sensors/types-of-voc-sensors-and-voc-sensor-technology/attachment/voc-sensors-302x230-1/#itempage>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.gdscorp.com/blog/voc-sensors/types-of-voc-sensors-and-voc-sensor-technology/attachment/voc-sensors-302x230-1/>