I used to live in an are with a large factory that processes timber then uses the splinters to create OSB and other wood composites. They also have a formaldehyde factory for producing their own adhesives. Since they came to the area, there are extremely weird smells that are hard to identify using only human sensors. Sometimes it smells like wood, sometimes like some weird steamy smell, sometimes like a sharp smell, sometimes like burned wood etc. I asked the local Environmental Agency and they say that their measurements show okay values for Formaldehyde, but they don't really have continuous measurements, so I find it hard to trust them. They also mentioned that Terpenes might be the reason why people smell different smells.
Now... I know this is a very complicated subject, but I was wondering what kind of substances could there be around? I would like to buy some measuring devices, but I don't really know what kind of instrument to get. Formaldehyde would be one of the compounds to measure, VOC's (which is actually a very broad term, as far as I can understand), but what else? What kind of substances might be generated by such a factory?