Incinerator chimneys were typically no more than 30 feet high. Steam plants burning coal tended to elevate their smokestacks such that the coal soot had a chance to dissipate and didn't "smoke out" buildings/houses in close proximity. Scrubbers? We don't need no stinking scrubbers. Back when I was in grade school in the 60s, the local Safeway grocery store had an incinerator behind it to burn boxes. Had a 2' diameter metal chimney maybe 15 feet tall - plus another 10' of similarly sized metal mesh to catch and retain flying matter. Those were the days before Denver was a smog infested shithole - likely contributed to the problem. Back then everybody burned their garbage.