Fire damage

Fire damage, in terms of the Baldur's Gate series, is an elemental or magical type of damage that circumvents any physical resistances.

Gameplay

 * Elemental and magical fire damage are handled separately, and not all spells and items cover both.
 * Resistances greater than 100% will heal the affected creatures, rather than harming them.

Protection from fire
Through the use of certain spells, items or abilities, it is possible to reduce the amount of damage, afflicted by fire.

Spells
Spells usually offer only temporary protection from fire, in varying degrees. … incomplete!
 * Elemental
 * Magical
 * Armor of Faith
 * Otiluke's Resilient Sphere
 * Elemental and magical
 * Resist Fire and Cold
 * Protection From Fire (arcane)
 * Protection From Fire (divine)
 * Fireshield (Red)
 * Sunfire
 * Protection From The Elements
 * Protection From Energy
 * Solar Stance (NPC only)

Items
Items, as long as equipped, offer a constant protection from fire. By wearing more than one of these, 100% resistance or even more is quite possible. Consumable items only give temporary protection. … incomplete!
 * Elemental
 * Batalista's Passport
 * Gift of Peace
 * Icingdeath
 * Mage Robe of Fire Resistance
 * Moonblade (NPC only)
 * Potion of Fire Resistance
 * Potion of Icedust
 * Potion of Magic Shielding
 * Protection From Fire (scroll)
 * Ring of Fire Control
 * Selune's Blade (NPC only)
 * Magical
 * Elemental and magical

Abilities
There are a few abilities that can offer temporary or constant protection from fire. … incomplete!
 * Elemental
 * Comet
 * Magical
 * Elemental and magical
 * Aura of Flaming Death
 * Storm Shield

Damage from fire
Many spells are based on fire, as well as some abilities, and items may deal bonus or even pure fire damage.

Spells
Due to their purpose of healing and supporting, the arsenal of fire-based spells is much smaller for priests than for wizards. … incomplete!
 * Elemental
 * Burning Hands
 * Chromatic Orb
 * Aganazzar's Scorcher
 * Flame Blade
 * Fireball
 * Flame Arrow
 * Flame Strike
 * Magical
 * Elemental and magical

Items
Regular weapons with fire damage, besides ammunition for bows, weren't introduced until Baldur's Gate II.
 * Elemental
 * Arrow of Detonation
 * Arrow of Fire
 * Club of Detonation
 * Dagger of the Star
 * Firetooth (dagger)
 * Flail of Ages
 * Flame Blade (item) (summoned by the spell of the same name)
 * Oil of Fiery Burning
 * Potion of Explosions
 * Potion of Fire Breath
 * Stonefire
 * Sunstone Bullet
 * The One Gift Lost
 * Wand of Fire
 * Wand of the Heavens

… incomplete!
 * Magical
 * Elemental and magical

Abilities
… … incomplete!
 * Elemental
 * Magical
 * Elemental and magical

Creatures, protected from fire
Some creatures have a natural resistance against fire damage, some have special items equipped that protect them. … incomplete!
 * Elemental
 * Balthazar's Solar Stance protects him completely from elemental fire damage.
 * Dradeel is able to cast a spell that produces a weapon, giving him 50% fire resistance.
 * Drizzt Do'Urden's Icingdeath gives him 50% resistance against fire damage.
 * Xan's Moonblade protects him at 50%, if it's the active weapon.
 * Magical
 * Abazigal can cast Armor of Faith with 25% resistance against magical fire.
 * Elemental and magical
 * Chromatic Demon: the fiend at Watcher's Keep has 100% resistance against both types in its Tanar'ri and Elemental Air forms and as Shambling Mound, but 0% as Ice Golem.

Creatures, dealing fire damage
There's is a number of creatures that always or by will are able to deal fire damage, either naturally, via spells or through special items in their equipment. … incomplete!
 * Elemental
 * Cambion: summoned by Amelyssan, this fiend will carry a two-hander that deals fire damage.
 * Demon Knight: the usurper of Durlag's Tower likes to throw Fireballs.
 * Duke Eltan will cast a Flame Strike if insulted.
 * Gatewarden: the guard of Candlekeep can be provoked into using a Flame Strike.
 * Kobold Commandos always have a limited number of Arrows of Fire.
 * Mirror Fiend: the (optional) final opponents in Durlag's Tower also like Fireballs.
 * Phoenix Guards: the summoned foes at the Nashkel cemetery will throw around Fireballs. They are also in possession of Arrows of Fire and Flaming Swords.
 * Ratchild carries some Arrows of Fire, though he prefers to cast spells rather than shoot.
 * Shandalar might use a Fireball.
 * Winski Perorate is able to cast a Flame Strike.
 * Magical
 * Elemental and magical