[Fish Sandwich]

Going back to check the episode, it seems Shouts subs messed up the line where Ichijou explains this, but the point of the smokestack is that Badzuu actively avoids being anywhere near the fumes, which is the reason he leaves before finishing off Kuuga. Evidently, either the Grongi aren't big fans of the Industrial Revolution, or maybe Badzuu in particular just feels that way since he's such a direct throwback to the original Kamen Rider, who was always meant to be a sort of champion of nature against the heartless technology of Shocker.

Either way, Kuuga being Kuuga, the police taking note of this ends up being relevant down the line, so hopefully it helps having this plot point cleared up.