Thankfully.
Quick review. The usual vendor claim is "Our materials all pass FAR 25.853(A) - 12 second vertical burn." or similar. That's the standard for upholstery and cabin sidewalls in passenger areas of Part 25 airliners. It means the material will self extinguish
after the heat source is removed. The test is conducted with a small burner; think Little Johnny playing with his father's Zippo.
It is important to understand that an FAR 25.853 material is not fireproof. It can and will continue to burn if the external heat source is not removed. As such, FAR 25.853 is not a suitable standard suitable for a firewall, or the floor immediately aft of the cooling air exit.
First, per FAR Part 23, the typical "hot spot" is 25 sq inches of firewall metal at 2000F, meaning vastly more heat energy than the vertical burn test. Second, and perhaps more critical, is that
the heat source cannot be removed. The pilot doesn't have any direct control of an engine compartment fire, or exhaust system failure.
As noted, there is plenty to read if you search VAF. Here's the quick version:
http://www.vansairforce.com/community/showpost.php?p=476353&postcount=20
Hands down, the best overall thermal performance for both ordinary comfort and fire protection to to place a reflector over an insulator on the engine side of the firewall. It probably also has some unmeasured effect on sound transmission. There is no safe
sound insulation for the cabin side.
BTW, theses are the FAR's applicable to firewall insulation:
? 23.1191 Firewalls.
(f) Compliance with the criteria for fireproof materials or components must be shown as follows:
(1) The flame to which the materials or components are subjected must be 2,000 ?150 ?F.
(2) Sheet materials approximately 10 inches square must be subjected to the flame from a suitable burner.
(3) The flame must be large enough to maintain the required test temperature over an area approximately five inches square.
(g) Firewall materials and fittings must resist flame penetration for at least 15 minutes.
? 23.1182 Nacelle areas behind firewalls.
Components, lines, and fittings, except those subject to the provisions of ?23.1351(e), located behind the engine-compartment firewall must be constructed of such materials and located at such distances from the firewall that they will not suffer damage sufficient to endanger the airplane if a portion of the engine side of the firewall is subjected to a flame temperature of not less than 2000 ?F for 15 minutes.