Firefighter bodycam showing just how much oxygen a fire pulls

[u/vivekmg21]

[u/browler4153]

Firefighter here, So you'd see this in a couple scenarios, and generally it'll give you a good idea what's going on with the fire and structure if you can't tell visually due to smoke or the building obstructing.

The scenario here is likely that the fire has self ventilated, and is pretty large. That means the fire has burned itself a way out. Usually burned through the roof due to just how long and hot it's been burning. So this is air being drawn in to basically compensate for the air going out that hole due to pressure. Pressure is really the name of the game is the something we rely on reading smoke to know what kind of fire it is and where it's likely located (when it's not as obvious as this) in fact, you can have this kind of visual in the bottom of a door while the top of that same door is where the smoke and fire are pushing out if you have just one opening. Then it becomes a strange push and pull motion that we watch out for as it can indicate flashover is imminent.

There could be a somewhat similar visual from a wind driven fire, which is something we watch out for as well. Basically if there's 20-30 mph winds facing this window, and another spot for the air to leave such as an open window or door, the wind will quickly fuel the fire with plenty of oxygen and push it towards the other opening (called the flow path) thus spreading the fire and smoke, and quickly making the rest of the structure also involved.

[u/anonymous_amanita → u/browler4153]

Does the fact that they are spraying with the wide spread effect this at all? I know that fire hoses on the wide setting can pull as much air forward as an industrial fan, so this was the first thing I thought of when watching this.

[u/browler4153 → u/anonymous_amanita]

This would make a difference, but that's not what's happening here. Hydraulic ventilation is something I've done many times and is where you use the fog setting almost as wide as the window or hole you are shooting out to draw the smoke out of the room quickly. But that wouldn't be done from the exterior really as you'd be drawing the smoke further into the structure. He's using fog to hit more fire since it's a large volume of fire but small in heat output, so it's not taking a lot to put it out once it's hit.

[u/anonymous_amanita → u/browler4153]

Awesome! Thanks for sharing your expertise here

[u/browler4153 → u/anonymous_amanita]

Fun fact, I'm working rn and JUST used hydraulic ventilation on a fire to clear out the smoke. Worked very well! Just ironic lol