Fire Resistance

Fire Resistance allows you to resist fire. The higher your Fire Resistance, the less damage you incur from fire-based attacks, such as from fire ants, or from enemies using fire-based weapons like the flamer, heavy incinerator, the Shishkebab, and Molotov cocktails.

Fallout 3

 * The Ant Might or Ant Sight perk can be acquired from Doctor Lesko during the course of the Fallout 3 quest Those!. Either perk grants +25% Fire Resistance.
 * Enclave Hellfire armor grants a +30% Fire Resistance and the Enclave Hellfire helmet a +5%.
 * Applying fire ant nectar will increase Fire Resistance by 25%.

If one has all three of the aforementioned flame-retardant abilities, the total will be 85% fire resistance, making enemies such as Enclave Hellfire troopers or fire ants little to no problem.

Fallout: New Vegas

 * Applying fire ant nectar will increase Fire Resistance by 25%.
 * Using gecko-backed armors from Honest Hearts  will increase by 15%.
 * The scorched Sierra power armor from Lonesome Road increases fire resistance by 25%.
 * Drinking an atomic cocktail will give you fire resistance as well as Energy Resistance.

Fallout 76
Fire resistance is an armor statistic enabled in the Fallout 76 update Patch 22. Fire resistance will reduce incoming fire damage based on a formula. Fire damage may be dealt by weapons like flamer or molotov cocktail, by creature attacks like floater flamers or anglers and by hazards such as the falling embers during A Colossal Problem. Scaling fire resistance has been added on all encounterable NPCs and creatures, however armor penetration options have yet to be implemented.

Player resistance
Fire resistance may only be acquired from the following sources:
 * The Sizzling Style legendary perk increases fire resistance by +50/100/150/200 while wearing a matching set of armor, depending on the perk rank.