Fire Resistance is a resistance status effect that cures and provides immunity to the burning status effect, as well as reducing elemental damage from fire by 25%.
Burn Resistance Spray applies this effect for 5 minutes. The Medical Kit applies this effect for 2 seconds. The Fire Resist Augment applies this effect as long as it is in use (without displaying the status icon).
There is a bug in Starbound's code that can cause fire resistance to backfire spectacularly and kill the player character. Starbound's code triggers 1 second of immunity for the player character if an attack does not cause knockback and causes greater than 10% damage to the player. Flame traps emit 10 fire particles per second, each of which causes 20 defense-ignoring damage. Ordinarily, a single hit is sufficient to trigger the 1 second of immunity, but if the player is using tier 6 armor, and the player uses anything that invokes burn resistance, then the fire's damage falls to 15, which is less than 10% of the player's health (160 with tier 6 armor), which means the player takes damage from each fire particle, or around 150 damage per second. If the player stacks burn resistance (e.g., by using a Fire Resist Augment and Burn Resistance Spray at the same time), then the fire's damage falls to 10, which means that the player takes damage from each fire particle, even if they're using no armor.