Dunno what you refer to exactly when using the term "PVC-clothing".
According to Wiki:
"In a fire, PVC-coated wires can form HCl fumes; the chlorine serves to scavenge free radicals and is the source of the material's fire retardance."
But I reckon with "PVC" you simply refer to synthetic fibres commonly used in clothing - and especially in those fancy coloured metallic shiny costume kind of stuff...
Yeah, it sucked when I tried to singe off a small string from my costume trousers and thereafter found myself trying to save the entire thing from getting up in flames. I decided not to use it as a firespinning-costume.
There recently has been the indecent of a Russian firespinner whose costume caught fire and she suffered from severe burnings, threatening her life.
Some precautions I would advise before attempting to prepare fire costumes from synthetic fibres, as obviously synthetic fibre does not equal synthetic fibre:
- Check a small piece of cloth (sample) for flammability
- Ideally treat the costume with fire retardant spray and
- Always use a cotton lining inside the costume
But foremost I would advise you to read this article
http://www.homeofpoi.com/lessons_all/teach/Library-Fire-Training-Fire-training-and-safety-Clothing-and-Costume-Fire-safety-1_2_140