Warzone? no, this is just the traditional Chinese Lunar New Year celebrations in Chinatown (San Francisco)
In fact it's not fog, it's thick rancid toxic smoke from pyrotechnics.
Each year, late on the night of the Chinese New Year, chaos erupts in the heart of Chinatown. An insane amount of very illegal firecrackers and fireworks are lit-up and detonated in the streets. The air fills-up with thick, rancid, toxic smoke. Sparks and rockets fly randomly in all directions. The local Police knows that they cannot stop the madness, so they prefer to stay away. Participants are highly advised to wear ear and eyes protection.
This unoficial event dubbed "Chinatown Bang" attracts local Chinese Americans as well as members of the San Francisco Cacophony Society. After running out of ammunitions, participants celebrate the Chinese lunar new year in local bars.