Okay, as chemist, physics guy and more, I would never have anything on wrist gauntlets or knees or helmets or jet packs or anything fly, fire, ignite, etc or you'll be the next winner of the Darwin Awards. You're really playing with 'redneck fire' and should not do it. There's a reason why most special effects are now CGI, the real deal is tricky, difficult to engineer and simply not safe to do.