Edy, by law, there has to be a FMVSS 302 additive to all plastics for vehicles sold in North America. Sure, it burns, but at a rate of less than 25mm per min or 1-inch per min. There are other criteria too such as how the fumes are gassed out and such. This additive allows folks in the vehicles time to escape should a vehicle caught fire.I'm 99% sure that all of it is flammable, luckily it's all protected behind the highly flammable ABS trim manufactured by Chrysler. The leather and vinyl are flammable, everything plastic is flammable, most of the fluids are flammable. I have a 65lb MDF enclosure for my 18" sub in the back that's flammable...
I do keep a 10lb ABC fire extinguisher in the trunk, my van has already caught fire once when a power steering line burst and sprayed onto the exhaust. I put it out before it caused any collateral damage, so I recommend to anyone to carry an ABC.
This also applies to fabrics, foams, trim and anything else in the interior. Even the HVAC pleated filters must be rated for this too. Some are even self-extinguishing.
Having non-FMVSS 302 materials all over the interior would allow the fire to be consuming very fast and hot. Getting to a fire extinguisher just after an accident may not be enough time.
I do like your ability to kill the outside sound and keep the cool or heat inside. Just the flammability worry's me some. I've seen 2 interstate vehicle fires in my life time. One set of folks got out, the others .... nope. They burned alive right before my eyes. Nobody could even get close enough to rescue them. sad sad sad.