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Air Pollution is produced by the Smoke Stack, Smoke Stack (Large), Flare, Burner (Solid) and Exhaust Scrubber. Every 20 units of Air Pollution released per month reduces Health by 1. Most sources of Air Pollution can be eliminated, although Exhaust cannot be rendered completely harmless, as the Exhaust Scrubber releases 24 units of raw Air Pollution per 180 Exhaust. Additionally, permanently sustainable factories which cannot dump Waste must instead use a Burner (Solid), producing 0.5 units of Air Pollution per Waste.
Below are all the recipes, which contain this item. Note, that some of them may be locked behind Research, and not immediately available in your game.