Casted Acrylic for Light Fixtures

Acrylic does burn and the fumes are toxic. I would recommend polycarbonate.

PMMA may serve the purpose of high impact,stiff & transparent in said application..

You need to look a little further for a flame proof transparent material. Few plastics(if any) will be suitable as well as transparent. Thin Teflon is good to 600F or so, and in thin sections is translucent, but not clear.

For mines and refineries you will need high temp silicate glass, which is clear and good to almost 1000C.

Suggest you search for suppliers and copy down the fire rating details they list on their products. Then search out those specifications from the regulating body and read it. They will list what you are allowed to use and the test methods and facilities you must use before you can market an item as flame proof to the specs.

Places like mine standards, UL, etc need to be looked at.

try these places.

http://en.wikipedia.org/wiki/United_States_Bureau_of_Mines

http://www.ul.com/

The Underwriters(insurance company test labs) labs will not allow anything to be used in a mine or refinery unless it meets the appropriate UL safety specs. UL has specs for tens of thousand of items from home and industry and in most cities you cannot sell stuff without UL certifications.