Fire Skills

Diablo II	Notation	Basic	Class	Skill	Item	Ally	Quest	Area	Monster	Tale

All Skills	Random Class Skills	Fire Skills	Skill bonus	Oskill	Aura Equipped	Charges	Charged suffix
Chance to Cast	On Attack	On Striking	When Struck	When You Die	Kill an Enemy	Level-up

Fire Skills increases the level of any skill classified as a Fire Skill:

Amazon	Assassin	Druid	Necromancer	Paladin	Sorceress
Fire Arrow Exploding Arrow Immolation Arrow	Fire Blast Fists of Fire Wake of Fire Dragon Tail Wake of Inferno	Firestorm Molten Boulder Fissure Fire Claws Volcano Armageddon	Corpse Explosion Fire Golem	Holy Fire	Fire Spells

No Barbarian skills are classified as Fire Skills.
Vengeance applies Fire Damage, but it is not classified as a Fire Skill (although +% Fire Skill Damage still applies to this damage).

Helm

Value	Source	Min Rlvl	Ladder
+3	Flickering Flame helm	55	No (D2R only)

Value	Source	Min Rlvl	Ladder
+2	The Rising Sun Amulet	65	No

Value	Source	Min Rlvl	Ladder
+1	Hellclap Short War Bow	27	No

Value	Source	Min Rlvl	Ladder
+1	Cathan's Rule Battle Staff	11	No
+2	The Salamander Battle Staff	21	No
+3	Leaf staff	19	No

Value	Source	Min Rlvl	Ladder
+2	Hellplague Long Sword	22	No
+3	Hexfire Shamshir	33	No
+3	Flamebellow Balrog Blade	71	No

Value	Source	Min Rlvl	Ladder
+1	Magefist Light Gauntlets	23	No