Add "setting fire to clothes" to the list of warnings subway riders should be warned of when they ride the trains: A 13-year old girl suffered burns when her jeans caught fire. She was riding a Queens-bound E train in the middle of the day, and subway workers suspect the fringe from the jeans got caught on the heater beneath the seat. A work told NY1, "The seat had to be extra hot from the train. You could look at her pants and see that any heat and any type of flame could get to the strands on the pants and catch fire." Firefighters came to the next station to put the fire out, and the girl was treated for minor burns. The train was taken out of service, and somewhere, there's a liar liar joke in this, but since it's a serious story, we won't find it.
Soot does not seem to be a factor in the Straphangers' Subway Shmutz survey. But even on a gross C train you should stop, drop and roll if your clothes catch fire.