Oxygen starving firefighting technique - GIF

[sossol]

It looks neat, but I don't understand this. Why are they spraying something out of the window? Is it water? Is it nitrogen? If they were inerting the atmosphere inside the building I would have expected them to spray something in. Is there a second hose supplying inert gas into a window on the other side of the building that we can't see? I have questions.

This is just an uneducated guess, but what I think they're doing is is using the mass and velocity of water to create a vacuum in the structure. The water "pulls" the air out faster than it can be replenished, so the fire is starved. The spigot has to be right at the opening to work, which is why the pole is shaped like a shepherd's hook. I assume that this would only work for mostly sealed enclosures, else it would draw in air from the other openings.

Neil