Flamethrower: Upon pressing primary fire, the weapon expels a stream of roughly 33.3 large flame particles per second in a narrow cone, at a cost of 12.5 ammunition per second. Flame particles are not obstructed by enemies or buildings owned by the opposing team, making it ideal for attacking multiple enemies. The range of fire is very limited (approximately 340 Hammer units when fired while stationary), but is capable of dealing heavy damage in close quarters.
Secondary fire causes the weapon to deliver a compression blast which deflects enemy projectiles, pushes opponents away, and extinguishes burning teammates. Deflected enemy projectiles deal mini-crit damage if they would not already be doing critical damage. If so, the deflected projectile deals critical damage. Each compression blast costs 20 ammunition, so it is possible to use 10 Compression blasts before needing to retrieve more ammo. Unlike the weapon's primary fire, the user can still use compression blasts if the weapon is directly in contact with a wall.
A Spy disguised as a Pyro still receives afterburn. Fire can be extinguished or (partially) mitigated in several ways. Afterburn from the Flame Thrower reduces healing from Medi Guns, Dispensers, and the Amputator by between 20% and 100%, with the reduction increasing in an inverse proportion to the amount of healing the item is giving. It also reduces the effects of the Vaccinator's ÜberCharge by 20%.