Deluge gun
![A deck gun in the foreground puts water through a window while a ladder-mounted master stream in the background directs water through the collapsed roof.](/Images/godic/202501/08/Deck_gun_on_American_fire_engine4246.jpg")
![Fixed fire monitor at a plastic manufacturing factory](/Images/godic/202501/08/Fixed_fire_monitor4246.jpg")
![](/Images/godic/202501/08/Deluge_gun4246.png")
A deluge gun, fire monitor, master stream, water cannon, or deck gun is an aimable controllable high-capacity water jet used for manual firefighting or automatic fire protection systems. Deluge guns are often designed to accommodate foam which has been injected in the upstream piping.