Upon pressing primary fire, the weapon will expel a stream of large flame particles at roughly 22.5 particles of flame each second, in what is roughly a narrow cone, at a cost of 12.5 ammunition per second. The range of the particles is much less than the range that the graphics suggest but is not obstructed by enemies or buildings owned by the opposing team, making it ideal for attacking multiple enemies. The range of the fire is very limited but is capable of dealing heavy damage at close quarters. At its maximum range, the Flamethrower is not accurate enough to put a constant stream on a single target. Note that the weapon cannot be used underwater; it will produce harmless bubbles.
Secondary fire causes the weapon to deliver a compression blast which can deflect enemy projectiles, push opposing players away, and extinguish teammates who are on fire. Each compression blast costs 20 ammunition, meaning it is possible to use 10 Compression blasts before needing to retrieve more ammo.
Flame damage is proportional to particle lifetime instead of distance from target. Unlike most weapons, critical hits are also affected by the scaling. Additionally, there is a very slight damage variance (±0.08/particle) due to differences in particle angles.
September 28, 2007 Patch
- Increased Flamethrower damage at point blank range.
- Fixed Flamethrower hit detection.
December 20, 2007 Patch
- Fixed the Flamethrower stuttering when firing directly into a building.
February 14, 2008 Patch
- Added Flamethrower "sizzle" sound when the Pyro is hitting a target.
April 29, 2008 Patch (Gold Rush Update)
- Fixed Flamethrower bug where a player flush against a wall couldn't be lit on fire from the front.
June 19, 2008 Patch (The Pyro Update)
- Added alt-fire compression blast to the basic Flamethrower.
- Tuned the Flamethrower hit detection to improve detection versus retreating opponents.
- Removed Flamethrower's damage falloff (was falling off to 25% by the end).
July 1, 2008 Patch
- Added back some damage falloff to the Pyro's Flamethrower. Not nearly as extreme as it was before the Pyro class pack.
March 5, 2009 Patch
- Fixed Flamethrower loophole that resulted in the flame effect being stuck on while the Flamethrower wasn't really firing.
May 21, 2009 Patch (Sniper vs. Spy Update)
- Flamethrower's air burst now extinguishes fire on friendly targets.
June 23, 2009 Patch
- A Pyro's air blast will now extinguish burning disguised enemy Spies, since knockback no longer affects disguised enemy Spies.
June 25, 2009 Patch
- Reverted airblast knockback on disguised Spies, so that they can once again be knocked back
February 23, 2010 Patch
- Fixed the Pyro not being able to deflect enemy flares.
April 28, 2010 Patch
- Flamethrower direct damage reduced by 20%.
- Burn duration reduced (10 -> 6 seconds).
- Airblast re-fire delay reduced by 25%.
- Airblast ammo usage reduced by 20%.
- All reflected rockets/grenades/arrows now Mini-Crit.
- Airblasting enemies into environmental deaths now awards the death credit to the Pyro.
May 19, 2010 Patch
- Increased base damage by 10%.
- Afterburn duration increased (from 6 to 10).
July 8, 2010 Patch (Engineer Update)
- Added better feedback sound for Pyros on when their Flamethrower is doing damage.
September 30, 2010 Patch (Mann-Conomy Update)
- [Undocumented] Pyro's Airblast pushes grounded stickies approximately twice the distance now.
December 17, 2010 Patch (Australian Christmas)
- Fixed a Flamethrower bug that allowed players to rapidly fake the Pyro's airblast effect.
February 3, 2011 Patch
- Updated model with optimizations and new LODs.
- [Undocumented] v_ and w_ model versions of the Flamethrower were removed and replaced with the newer c_model variant.
February 7, 2011 Patch
- Fixed burning deaths to always use the death notice icon for the weapon that started the burn.
July 12, 2011