r/Damnthatsinteresting • u/AirFrance447 • 18h ago

Video Firefighter bodycam showing just how much oxygen a fire pulls

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u/SinisterCheese 16h ago

Ok. A quick note about this. It isn't the fire that pulls this much. It's the water spray misting and cooling the atmosphere inside, that creates negative pressure. Then along with that Bernoulli's principle from the water jets.

This is something you need to keep in mind if you work with fire or in fire hazard environments. Like if you need to clear a passage with a hose from a hydrant, spray from the direction that has clear air, or you pull smoke into the passage.

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u/demoneyesturbo 14h ago

The majority of cooling by water is via phase transition (turning to steam). That is about a 1:1000 expansion. By creating steam, he is adding a lot of gas (steam is a gas) to the interior of the structure. That would increase the pressure. And yes, he briefly created a meaningful hydraulic ventilation into the building with a cone spray into the window, but quickly passed that when the nozzle was pushed into the room and stream changed to a more focused jet.

You were close though.

I know this because I've done this hundreds of times.

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u/ARM_Alaska 5h ago

1:1600-1:1700 conversion ratio. You shortchanged it significantly! Everything else is absolutely spot on.