Fire

Fire or Flames refers to the special particles produced by the Pyro’s primary weapons. When these particles connect to an enemy player, a damage-over-time effect (sometimes called a DOT) called Afterburn is applied. Fire has its own damage type, and some other weapons which aren't Pyro primary weapons also have fire-like properties.

A Burning Spy.

Flame mechanics

When the fire button is pressed with the Flamethrower, a stream of invisible particles launches out at a speed which depends on the attcking Pyro's own speed at the time of launch. These invisible particles differ from the visual fire which can be seen in-game. When one of these fire particles makes direct contact with an enemy player's hitbox, they take damage and have a visual indication of being on fire. Unlike other projectiles, fire does not stop when colliding with the environment, and instead keeps moving until the flame particles have reached their maximum lifespan.

The momentum of fire particles as stated earlier depends on the Pyro's own momentum. When a player is moving, the player's momentum is factored, meaning a Pyro walking forward while firing these particles will increase their speed, thus extending their range. Moving backwards does the same in the opposite direction, reducing the fire particle speed.

Afterburn

Afterburn is a DOT effect which can be inflicted with the stock Flamethrower and the Flare Gun. When an afterburn-causing attack lands, the target is set aflame with a visual indicator. Upon being set aflame the lit character in question will yell that they are on fire, alerting nearby Medics and teammates. Setting an opponent on fire disorients targets on fire as flame effects appear on the edge of their screen, and shakes their screen with each tick of Afterburn. This is especially frustrating for enemy Snipers as the scoped view while on fire will move every time the Sniper takes burning damage, making it much harder to aim. When a burning player calls for Medic, their Medic speech balloon will be on fire, notifying the Medic that a teammate is on fire.

Afterburn is a particularly effective Spy Checking tool, as invisibility or disguises are not immune to afterburn. A Pyro wishing to spy-check an area can spray flames in all directions, and any Spies will be lit. Burning players give off additional effects showing a player's true allegiance. This is useful to distinguish friendly Spies who are on fire and enemy Spies.

Afterburn can be extinguished in a variety of ways. The Pyro's own Airblast can extinguish teammates, so can health packs which instantly extinguish Afterburn, water in certain maps (e.g. 2Fort sewers), and any source of healing can out-heal the damage Afterburn does. Any source of healing can heal a burning teammate, giving them the health to tank the Afterburn damage and survive. It is also possible that if the enemy Pyro is wielding the Harvester, killing the Harvester-wielding Pyro will extinguish all enemy players, no matter where the Afterburn originated from.

Afterburn takes effect upon taking damage from a weapon that causes it. Afterburn does 3 damage per tick, or 6 damage per second. The duration of Afterburn from Flamethrowers always stays the same no matter how many fire particles make contact, lasting around 10 seconds. Same is true for the Flare Gun. This means the total Afterburn damage is 60 damage unless the burning player manages to extinguishe themselves.

Afterburn does not crit, however it can mini-crit if the Afterburn-causing damage is mini-crit boosted or the target is marked for death.

Note that Pyros are immune to Afterburn. Afterburn will tick once, and then the Afterburn will automatically be extinguished.

The Harvester regenerates the Pyro wielding it's health, approximately 5 per tick, or 10 health per second while held out. This also charges the HEAT meter on the Harvester; when fully charged the Harvester gets 1 guaranteed Critical Hit. This Critical Hit is only used up when hitting an enemy player, even if the swing has missed.

Weapons that can inflict Afterburn

{main|List of weapons}}

Name	Picture	Class	Notes
Flamethrower		Pyro
Flare Gun		Pyro
Huntsman		Sniper	Hunstman arrows only cause Afterburn if they are lit, either by a friendly Pyro or with certain map elements (e.g the torches on DeGroot Keep)

Related weapons

The following weapons have interactions based on Afterburn or fire damage.

Name	Picture	Class	Notes
Harvester		Pyro	Harevster "harvests" afterburn off of both living and dead players, regenerating the Harvester wielding Pyro's health and building the HEAT meter. Harevester Pyros that are killed extinguish the entire oposing team.
Huntsman		Sniper	Hunstman arrows cause Afterburn if they are lit, either by a friendly Pyro or with certain map elements (e.g the torches on DeGroot Keep)
Invis Watch		Spy	Cloaking while on fire will half the duration of the status effect.

Related achievements

Achievement		Description
	A Burning Memory	As a Pyro, deal 1000 afterburn damage while you're dead.
	Molten Steal	Land a Flare Gun crit on an enemy that somebody else set on fire.
	Summary Execution	Decapitate all 9 classes with the Harvester. Scout Soldier Pyro Demoman Heavy Engineer Medic Sniper Spy
	Head Rush	Decapitate 3 enemies with the Harvester in a single life.
	Don't Fear the Reaper	Save 5 teammates from burning to death by killing enemy Pyros wielding the Harvester.
	No, Time to Die	As a Spy, extinguish yourself by killing a Pyro wielding the Harvester.