Fire

Fire is a hazard in the Pikmin series. Most Pikmin types are not resistant to fire, and if they touch a fire source, the top of their stems will begin to burn up, they will run around in a panicked state, and if not saved, will eventually succumb and die. They can be saved by being whistled at. Red Pikmin, Glow Pikmin and Bulbmin are completely immune to fire, making them necessary to handle obstacles or enemies that can produce or are under fire. Ice Pikmin burn quicker than other types.

Leaders are not normally invulnerable to fire hazards: they will take damage and be knocked back if they touch fire. However, by salvaging the Scorch Guard, they will be rendered completely immune to fire. However, they can still be stunned by the Titan Dweevil's Flare Cannon.

In Pikmin 2, Pikmin that are on fire will not be affected by explosions.^[1]

Sources

Some obstacles and enemies can generate flames, while others are constantly burning up.

Fire geyser – geysers poking from the ground that spit streams of fire.
Fire starter – small pinecone objects which can only be carried by Red Pikmin in Pikmin 4.
Flames – flame-covered floors, blocking the way until they are put out.
Sizzling floor – circular patches of red-hot ground that will constantly burn unless destroyed.
Olfactory Sculpture – a candle treasure with an active flame.
Fiery Blowhog – enemies capable of spitting flames.
Fiery Dweevil – enemies that burn up temporarily when threatened.
Fiery Bulblax – grub-dogs that are constantly on fire.
Pyroclasmic Slooch – slug-like enemies that are always on fire. They also leave behind a trail of flames.
Scorchcake – mollusc-like creatures whose underside is covered in fire.
Titan Blowhog – massive Fiery Blowhogs whose fire breath has a larger range.
Fireflap Bulborb – flying creatures covered in fire.
Fiery Dwarf Bulblax – dwarf version of the Fiery Bulblax.
Firesnout Beetle – insects that shoot flames from their mouths.
Fiery Young Yellow Wollywog – Young Yellow Wollywogs covered in flames.
Titan Dweevil – the final boss in Pikmin 2 has an attack that can spew out fire like a flamethrower.
Plasm Wraith – the final boss in Pikmin 3 can spit out fire Elemental Plasms.
Ancient Sirehound – the final boss in Pikmin 4 uses fire in its fourth phase.

Scorch Guard

Main article: Scorch Guard.

The Scorch Guard is a spacesuit upgrade in Pikmin 2 Pikmin 3 and Pikmin 4. After it is collected, the playable leaders will gain immunity to all sorts of fire attacks, just like Red Pikmin. The exception is the Titan Dweevil's Flare Cannon, since it will stun leaders, even if it doesn't harm them.

Red Pikmin

Main article: Red Pikmin.

Red Pikmin are resistant to fire, meaning they will not be affected by any flame and will act as if it does not exist. Glow Pikmin & Bulbmin also share this trait. This makes them quite valuable when fighting against fire-related enemies and overcoming fiery obstacles. Unlike other Pikmin types that can resist a certain hazard, Red Pikmin cannot use fire to their own advantage, nor can they interact with it.

In the Super Smash Bros. series

This article or section is a short summary on fire attacks.
SmashWiki features more in-depth content.

Some fighters in the Super Smash Bros. series have attacks that can set their opponents on fire. Olimar is one of them – when a Red Pikmin attacks an enemy, it burns them. Similarly to the Pikmin series, Red Pikmin can completely resist any attack with a fire property, by taking no damage and not flinching, although other Pikmin types do not take any extra damage from fire attacks.

Glitches

Shifted heat haze: in New Play Control! Pikmin 2 exclusively, fires that aren't horizontally centered on the camera will have their heat haze effect shifted away from them.
Drowning cutscene glitch: in Pikmin 3, if the drowning explanation cutscene plays while there is a trail of fire near the water, if the camera aligns correctly, the fire and water's depths will not be calculated correctly, and the water splashes will appear on top of the fire.