That's some chili.
Fire fighters in central London were called out in full hazmat gear when they received a report that a) something was on fire, and b) it was causing knocking down everyone that was within range of the cloud. Knocking down as in, "couldn't breathe, couldn't see, in lots of pain."
At 1900 local time they had pinpointed the location (the Thai Cottage Restaurant) and the source of the noxious smoke: A cooking pot containing about nine pounds of nam prik pao, which is a Thai dipping sauce made up of super-hot chili peppers that are fried until they are burned, almost until they are on fire.
Gee.. those symptoms sound a lot like getting maced, come to think of it.
As it turns out, the people who work at the restaurant are used to the smoke, so they didn't notice that it was causing immense distress in everyone within range of the outlet of the restaurant's ventilation system.