Fire

A Burning Spy.

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 that aren't Pyro primary weapons also have fire-like properties.

Flame mechanics

When the fire button is pressed with the Flame Thrower, a stream of invisible particles launches out at a speed that depends on the attacking Pyro's own speed at the time of launch. These invisible particles differ from the visual fire that 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 in, 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 that can be inflicted with the stock Flame Thrower 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 shake their screen with each tick of the 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 friendly Medics that a teammate is on fire and in danger of dying to afterburn. Pyros are immune to afterburn and only take 1 tick of fire damage before they are automatically extinguished.

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 from enemy Spies.

Afterburn can be extinguished in a variety of ways. The Pyro's own airblast can extinguish teammates, as can health packs that instantly extinguish afterburn, water on certain maps (e.g. 2Fort sewers), and any source of healing that can out-heal the damage afterburn does. Any source of healing can heal a burning teammate, such as the medibeam or a Dispenser, 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 the afterburn from Flame Throwers always stays the same, no matter how many fire particles make contact, lasting around 10 seconds. The same is true for the Flare Gun. This means the total afterburn damage is 60 damage unless the burning player manages to extinguish 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 its 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 been missed.

Weapons that can inflict Afterburn

Main: Weapons

Name	Picture	Class	Notes
Flame Thrower		Pyro
Flare Gun		Pyro
Huntsman		Sniper	Huntsman 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	Harvester "harvests" afterburn off both living and dead players, regenerating the Harvester wielding Pyro's health and building the HEAT meter. Harvester Pyros that are killed extinguish the entire opposing team.
Flare Gun		Pyro	The Flare Gun does critical damage to any burning target, no matter the distance.
Huntsman		Sniper	Huntsman 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 afterburn.

Strategy

This will primarily focus on afterburn startegy. For strategy with the Flame Throwers, see the Pyro page.

• Afterburn can be used during hit-and-run maneuvers to great effect, allowing players to avoid direct confrontation while dealing considerable damage over time. This is even easier due to the fact any spray of flames inflicts full afterburn, no natter the time being sprayed with flames.
  • Hit and run strategies can be done even easier with the Twin Barrel. This means a Pyro can Twin Barrel jump in, set enemies on fire, and jump away.

• As said earlier, it proves to be a useful tool for seeking out cloaked or disguised Spies, who will burn and will remain obvious whether cloaked and even while disguised.

• Afterburn caused by ranged weapons such as the Flare Gun or lit Huntsman arrows can be used to make life impossible for enemy Snipers as the flinching from burning makes aiming significantly harder.

• Afterburn allows Harvester-wielding Pyros to heal back health as well as charge the HEAT meter. This makes a hit-and-run startegy even more effective, as this allows Pyros to light enemies on fire, and run while healing back whatever damage they took. This can be done with the Twin Barrel as well.
  • Flares also charge up the Harvester, allowing across-the-map flare shots to allow a Pyro to heal while staying safe from harm.

• Flares deal critical damage to burning targets. This can be used at long range to kill enemy Snipers, but this can also be used at close range in combination with a Flame Thrower for burst damage. Its best to use the Flame Thrower as it is easier to light people at close, then use the Flare Gun to finish them off.

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.

Update history

2.1.3

• Raised afterburn condition duration for Pyros to 0.5s (from 0.25s)
  • This allows for Flaregun^(sic) combos in certain situations
• Damage over time conditions (bleed, afterburn) no longer apply on the very same tick as damage