Ditto w/ what eclypse said.
Fire-......ant textiles are treated with chemicals for that purpose, and the chemicals will almost certainly seep into your
e-liquid -- giving you a toxic mouthful and eliminating the "fire-resistance" as well.
(With Duvetyne fabric, for instance, you're not supposed to wash it because the treatment will wash off as well. The PG could act as a very quick solvent to whatever fire-resistant additives are in the polyfill.)
I'd say it's better to use something that won't
thread off (like polyfill) and risk getting into your atomizer in the first place. If you have a material that stays put in the cart and doesn't unravel at all, it won't risk burning anyway.