Compression blast

From TF2 Wiki

The Compression blast, which when successful results in a Deflection, is an ability exclusive to the Flamethrower that allows the Pyro to use a blast of compressed air to send flying Rockets, Grenades, Sticky bombs and Flares back at the enemy with a click of the alt fire button, consuming 25 ammo each time. Rockets fired from a Level 3 Sentry can also be deflected. The deflected projectiles can be used to damage the enemy. The deflection ability is especially useful for protecting Sentry guns from attacks by Soldiers and Demomen.

If used on an enemy player, the compression blast will knock them back through the air for several feet, allowing you to potentially juggle and finish off the player, or blast them off cliffs and capture points. This ability is highly useful for separating medics and their patients and neutralizing ÜberCharged enemies.

With some exceptions, deflected projectiles are considered to have been fired by the Pyro deflecting them for the purposes of friendly fire and kill awards. For example, a red Grenade will turn blue when deflected and will hurt any RED-team players near it when it explodes. It can also hurt the Pyro who deflected it, in the same way that a Demoman hurts himself with his own Grenades. Deflected projectiles are just as powerful as before they were deflected.

The unlockable flamethrower alternative, the Backburner, lacks this ability.

Exceptions

With Stickybombs, the bombs can be thrown or pushed along the floor, but they do not switch ownership. The only change to a deflected Stickybomb (besides being moved) is that if the Demoman who shot it is blown up, it counts as a kill for the Pyro rather than a suicide.

Aiming

When a projectile is deflected, it is not simply "bounced" as if from a mirror: The Pyro can actually aim it to a new location. For example, a deflected rocket (or Flare) is essentially stopped and "re-fired" from its current position, aimed directly at a point on the nearest surface under the Pyro's crosshair. A skilled or well-positioned Pyro can even make rockets deflect at right angles to their original path.

The ability to aim projectiles is somewhat less useful with Grenades due to their arcing trajectory, and further testing is needed to see if they behave similarly.

Compression Jumping

As it is possible to redirect rockets with the compression blast, it is then also possible to redirect them in such a way that a Pyro can mimic rocket jumping. It is exceptionally difficult to do in comparison to other explosive-assisted jumping, as the Pyro must have the fortune of being in the right position to an incoming rocket as well as reflecting it in the proper direction. If pulled off correctly, it is possible to get a good amount of kick out of the reflected projectile and fly quite far.