- Not to be confused with Blue Fire from Ocarina of Time
In Breath of the Wild, a Blue Flame is a special type of fire created from a strong energy deposit, known as Ancient Furnaces, that is required to fuel the furnaces at both the Akkala Ancient Tech Lab and the Hateno Ancient Tech Lab.
Blue flame may be found to the west of Zelkoa Pond, north of Hateno Village in Hateno province, as well as Tumlea Heights in Akkala province, to the west of the tech lab. Blue flames can also be found in other locations throughout the game, such as within Divine Beast Vah Rudania.
When the furnace at the Hateno Ancient Tech Lab is lit, the Guidance Stone there is able to unlock the camera rune on the Sheikah Slate, as well as provide upgrades to the Stasis, Cryonis and Remote Bomb runes. When the Akkala Ancient Tech Lab's furnace is lit, Cherry is reactivated and can produce ancient soldier gear for Link.
Aside from its special function of heating the ancient furnaces, Blue Flame behaves identically to normal fire and can be used to set various things on fire or act as a light source via Link's torch. The ensuing flames (save from the source) are regular-colored and not blue. If no torch is available, the blue flame will consume wooden weapons at the same rate as regular flame (1 min).
It's implied that the source of energy that produces the Blue Flames is precisely what powers the multitude of Ancient Sheikah Technology constructs across Hyrule including Shrines, Towers and even the Divine Beasts, as well as the ancient and guardian weapons found at both the Akkala Ancient Tech Lab and from the various Guardian Scouts at the Test of Strength Shrines.