Voc might work. It covers most things you can smell. If it’s a sulfur smell, it’s probably sewer gas from something decomposing or fertilizer (or an unrelated

Voc might work. It covers most things you can smell. If it’s a sulfur smell, it’s probably sewer gas from something decomposing or fertilizer (or an unrelated sewer problem near the facility), and a natural gas / propane detector should work. They also pick up methane, which is odorless, but is probably being produced by the same source.