Fireproof

From the Call of Duty Wiki

Fireproof is a Call of Duty: World at War perk which reduces fire damage from burning objects, Molotov cocktails and the M2 Flamethrower. Those who have had Flamethrowers and Molotov Cocktails used against them often should probably use this perk. It is unlocked at level 48. It is fairly over looked and under used. Many players think this is a waste of a Tier 3 perk slot due to the rarity of encountering such weapons, however it can be useful if it is guaranteed that the player will encounter enemies with Molotovs and/or Flamethrowers (such as in Private Matches). This perk makes you be able to survive 5 hits from a flamethrower, thus allowing you to survive up to 2 seconds before being killed by a flamethrower (see M2 Flamethrower link for more info).

Perks of Call of Duty: World at War
Tier 1 Perks	Special Grenades x3 · Satchel Charge x2 · M9A1 Bazooka x2 · Bomb Squad · Bouncing Betty x2 · Bandolier · Primary Grenades x2 · M2 Flamethrower
Tier 2 Perks	Stopping Power · Fireworks · Flak Jacket · Gas Mask · Juggernaut · Camouflage · Sleight of Hand · Shades · Double Tap · Overkill
Tier 3 Perks	Deep Impact · Extreme Conditioning · Steady Aim · Toss Back · Second Chance · Martyrdom · Fireproof · Dead Silence · Iron Lungs · Reconnaissance
Vehicle Perks	Water Cooler ·Greased Bearings ·Ordnance Training ·Leadfoot ·Coaxial Machine Gun
Kill Streak Perks	3: Recon Plane · 5: Artillery Strike · 7: Dogs