Woman dies after being set on fire on NYC subway; Person of interest taken into custody, police say

I've been trying to find out more about this because the story doesn't make any sense:

"he approached the sleeping woman, and then lit her on fire with what was believed to be a lighter. She added the victim's clothes became fully engulfed in a matter of seconds."

Clothing shouldn't just be flammable like that without some kind of accelerant.

https://www.cpsc.gov/Regulations-Laws--Standards/Statutes/Flammable-Fabrics-Act