Well how long do you expect your car to be on fire? We're not talking about this foam spontaneously combusting. It's also not going to catch fire from hot exhaust or staying in the sun. What these fire ratings are, is if you apply a fire to the foam, does it catch fire itself. This foam isn't any more flamable that the seats/carpet/plastics in your car, and must less than the brake fluid and fuel running around.

And besides, that foam won't work. The poly foam that we're using uses a catalyst reaction to harden and cure. It doesn't need air. That foam and stuff like "great stuff" need air to dry. Go fill up a clear plastic cup with great stuff and it'll only dry and harden about 1/2" down. The rest will still be liquid. The hardening reaction is much like fiberglass. It gets pretty darn hot when curing. Even when dissipating that heat to the chassis.