In case of emergency...

Place plastic bag over head and cinch tightly. In a few moments your oxygen will run out and you will not care about the emergency.
Found in every subway station, our best guess is that these bags are meant to be employed should the subway ever fill with smoke or other noxious fumes. Of course, at any given time, there is at least a few hundred people milling about the platfrom, and a thousand or so more on the train itself. There looks to be about a dozen bags at each of the station's four emergency posts. Like Shakespeare and St. Valentine before him, Darwin was at least half (the recessive half?) Korean.