What factors generally determine how long the smell of fire persists in the tunnel near the nearest subway stations?

Hello, What factors generally determine how long a burning smell (from a burnt-out subway car) persists in the middle of a tunnel at the nearest subway stations? https://www.5min.at/5202411211329/u1-brand-in-wien-was-war-die-ursache/

Berlin S-Bahn was ablaze – why is that?

https://www.reddit.com/r/berlin/s/RBASk0AIAC Woman smoking on the subway – massive fire despite flame-retardant materials? Hard to imagine in modern times with strict regulations Woman is said to have smoked crack – but does that mean a whole car burns down? How could such a major fire occur? The S-Bahn is actually made of special materials that don't…