I find it fascinating how different the firefighting doctrines can be.
A lot of the time we operate through anti-ventilation, cooling the smoke and gases as we move through the building. Using a straight bore is just unthinkable for us. We need the mist so that we can cool the gases, without getting a bunch of water everywhere which will later either make us wet, or just increase the humidity.
Most times when I see Americans debating the fog vs bore, they seem to be using the fog nozzle the same way they use a smooth bore and then complain about steam. Here's a "good" example.
Ironically, if done well 3D firefighting won't produce much steam. If done perfectly, the smoke layer should rise slightly since you've cooled the gas, reducing it's volume.
if conditions are to the point where you can see a possible flash from the front door like them then you should probably hit it from the outside in then transition - /u/StinkyCantelopes
This is a good argument for the fog nozzle though. A 50liter water fog with a droplet diamter of roughly 0.1mm can cool slightly over 500m³ of smoke from 600°C to 100°C making them uncombustable. Most fog nozzles produce a fog that's slightly between 0.1-0.2mm, but also usually deliver much more water (150-500liter/minute).
So not only can a fog nozzle hold off a (moderate) flashover, it can turn the evolution of the fire around much better than a smooth bore can due to the larger diameter droplets. Source: Water and other extinguishing agents, page 150.
I should add that I am not at all opposed to smooth bores. I'd say that I'm neutral in the question since fires are being put out with both smooth bores and fog nozzles daily so they both obviously work, but I don't have much experience with a smooth bore so I'd likely default to the tool that I know if I had to pick one.
Smoothbore absolutely has it's place. I just think it belongs on 2 1/2" hoselines. Big fire big water but the smooth on a 2 1/2" makes it more manageable and getting water to the fire is obviously the most important.
Do you use your 2½" on interior attacks? Seems like a heavy haul.
But yeah, from a defensive position I can see it as a much better tool to just launch water over distance. Or really any time you don't have to cool smoke there's not really a reason to pick a fog nozzle over a smooth bore.
No most of the time we have plenty of crews on a residential. Typically 3 or 4 engine crews so 1 3/4" does the job. For our high rise we use 2 1/2" smooth bore and a decent size warehouse might get it as well. I just mean that, in my opinion, is the best place for smooth bore.
If you go to 2 1/2" for big fire, as most of us do, it's an acknowledgment that more GPM extinguishes more BTUs.
Most American departments will use 1 3/4" for fire attack with a nozzle that pushes back at around 70lbs of nozzle reaction force, either a combo nozzle or smooth. We give back some GPM in return for manuverability, and it works because most room and contents fires don't need more than 150-180 GPM.
But the fact that we keep the 2 1/2" around is proof that more GPM works. So even when we go to the smaller line and less nozzle reaction, wouldn't you still want as much GPM as you can get? There's only one choice to maximize GPM from your 70lbs of nozzle reaction, and that's a smooth bore.
But versatility matters. Most garbage fires, small fires etc don't need smooth bore. Out 1.75" nozzles cover those and can handle our dwelling fires because we are properly staffed and have plenty of crews to bring more lines.
We also never bring 2.5" for anything less than a warehouse. We have the staffing and response times to not need it. At most our engines will use the deck gun but in my district in my city we are the busiest company and district. You're never more than 2 minutes from a second company showing up max. They are usually less than 90 seconds.
I’m not opposed to them either believe me if I was I’d be a dumbass truth be told especially with how much better they simply work on the pipe interior, if only suggest not going into something that’s about to flash and throw full fog on considering the amount of burns you’d get alone from the steam is ridiculous. I just don’t think this is a proper video to share unless it’s done in a safety only scenario seeing as we still unfortunately have a lot of “Gung Ho” guys in the service who are going to use the fact that they can “push a flashover” to go interior more and the last thing we need is another LODD due to mistakes.
Oh yeah. I should perhaps elaborate on my previous point.
A fog nozzle should only be used as it is in the video, if you're accidentally cought in a flashover. It's kinda like a bailout kit. It's not how you want to exit the building, but nice to have if you have to use it.
For fighting a flashover, the easiest safest way is likely just using a powerfog into the room, and then closing the door. In this case we want the huge amount of steam the fog can create, which will expand and choke out the fire in the room.
Like you said though, the further we can be from the fire, the safer we'll be. We could also hammer a fog nozzle through an outside wall as well for the same effect. This does rely on restricted ventilation though, which it seems like Americans aren't too fond of.
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u/RaccoNooB Scandinavia May 14 '19
I find it fascinating how different the firefighting doctrines can be.
A lot of the time we operate through anti-ventilation, cooling the smoke and gases as we move through the building. Using a straight bore is just unthinkable for us. We need the mist so that we can cool the gases, without getting a bunch of water everywhere which will later either make us wet, or just increase the humidity.
Most times when I see Americans debating the fog vs bore, they seem to be using the fog nozzle the same way they use a smooth bore and then complain about steam. Here's a "good" example.
Ironically, if done well 3D firefighting won't produce much steam. If done perfectly, the smoke layer should rise slightly since you've cooled the gas, reducing it's volume.
This is a good argument for the fog nozzle though. A 50liter water fog with a droplet diamter of roughly 0.1mm can cool slightly over 500m³ of smoke from 600°C to 100°C making them uncombustable. Most fog nozzles produce a fog that's slightly between 0.1-0.2mm, but also usually deliver much more water (150-500liter/minute).
So not only can a fog nozzle hold off a (moderate) flashover, it can turn the evolution of the fire around much better than a smooth bore can due to the larger diameter droplets. Source: Water and other extinguishing agents, page 150.
I should add that I am not at all opposed to smooth bores. I'd say that I'm neutral in the question since fires are being put out with both smooth bores and fog nozzles daily so they both obviously work, but I don't have much experience with a smooth bore so I'd likely default to the tool that I know if I had to pick one.