If there's a terrible smell, it should be detected by a $100 off-the-shelf TVOC air quality meter, the type that can detect perfumes. Have you tried one? If y

If there's a terrible smell, it should be detected by a $100 off-the-shelf TVOC air quality meter, the type that can detect perfumes. Have you tried one? If you know which specific gases may be present in the plant exhaust, there may be an existing low-cost (~$50) sensor [1] which can be assembled in a custom DIY air quality monitoring circuit like AirGradient (who post on HN). There are consumer particle counters (0.5 micron) for about $300, which have a serial port for continuous data logging. > setup monitoring in their property, which they'd never allow Once there's a low-cost (sub $500) continuous air quality data recording device, then 4 of those devices in different directions from the plant, along with local wind data, could show a pattern over an extended period of time. In theory, wind-borne flying objects like kites and drones could also collect data on air quality indexed by GPS location. [1] MQ series of gas sensors: https://www.open-electronics.org/presenting-mq-sensors-low-cost-gas-and-pollution-detectors/ https://www.open-electronics.org/presenting-mq-sensors-low-c...