Interesting stuff.

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Posted by Ambulance Driver on July 6, 2012 • Filed under: Fire Rescue Topics, Firefighting Operations

Old_NFO

It will be interesting to see these results… We used to use a military fog nozzle poked through a broken window pane to knock down rooms… Wonder if that is one of the things they will try??? Military has used that technique for years in shipboard fire fighting!
http://zercool.blogspot.com/ ZerCool

And next week, we’ll try high-pressure fog … again.

I see the point they’re making and I’m interested in the results, but here’s the issue I see:
- small fire starts, consumes lots of fuel, available oxygen, and returns to smoldering in a room north of 1000F.
- nozzleman comes in low and opens up a straight-stream.
- a whole damn lot of that water is converting directly to steam – at a 1700:1 expansion ratio*.
- that steam has nowhere to go and quickly parboils the firefighters.

Ventilation isn’t just about the fire gases and smoke; it’s about cooling the room.

* – a cubic foot of water is about 7.5gal; a standard handline flows 150-200gpm or about 20cu.ft./min – or a cubic foot every three seconds. A typical 12×16 master bedroom with 8-foot ceilings is 1500cu.ft. … so in THREE SECONDS of handline flow, enough steam has been generated to entirely displace the atmosphere of the room – but nowhere near enough to effectively cool the room below combustion temperature.
Gaffer

The mixed (paid & volunteer) department I served with (many years ago) made it standard practice to use a fog pattern through the basement window. While it wasn’t the best solution it did cool down the area so that an interior attack could be made.
Matt G

Zercool speaks to what they call Hydraulic Ventilation– pushing the smoke (and heat!) out the far side with the fogged water. Done right, it takes cooperation: “Hey, open the far side on three, while I open the nozzle at the same time. Ready? 1-2-3!” One thing that they didn’t mention in that article is that releasing that smoke at the same time as the heat actually robs the fire of lots of fuel… the smoke itself– which flashes over at about 1100 degrees.
ZerCool

Nope, hydraulic vent (effective but messy and uses a lot of water; better after the fire is knocked down – especially so you don’t upset the thermal stratification) is different. I’m talking about High Pressure Fog. It was real big in the 70s if memory serves, and a quick search looks like it may be trying to make a comeback.

Basically, instead of 150gpm at 100psi, it’s 5-10gpm at 1000psi in a very fine fog. The intent is that it will flash to steam and displace the oxygen, smothering the fire. The downside is, as mentioned before, that it really doesn’t cut the heat by much, and it also takes a pretty well-sealed room to really make it effective.

We joke about the fire service being 150 years of tradition unimpeded by progress, but the truth is, as a profession we’ve come a LONG ways. Leather buckets were supplanted by man-powered pumpers were supplanted by steam-powered pumps to motor-driven. Single- and dual-stage pumps that can move 2000gpm at 150psi. Rubber boots, long coats, and leather helmets have turned into Nomex and PBIGold and kevlar-matrix and fiberglass. Getting lungs full of soot and smoke is a thing of the past with SCBAs that last 30 minutes and weigh 35lbs. (Ask for one of the wireframe packs with a steel bottle sometime to see the difference there.) PASS alarms used to be separate, now they’re integrated in our packs (and we all learn the firefighter sway in basic), and now they have integrated a “find me” beacon. Trucks went from open cabs and riding the step to Cincinnati cabs and enclosed crew cabs for 4, 6, even 10 crew.

Now, socially, we’re still retarded … but that’s for too much for one comment.
NYEMT

This is stuff that fire service instructors have been teaching for 15 years. FDNY has clung to their tactics for decades, and it works (mostly) because of the type of buildings and the style of construction hasn’t changed significantly.

New York’s two- to four-story, multi-family residences and “taxpayer”-type structures (business at street-level, apartments above) were, for a hundred years, primarily masonry-built with relatively small rooms, and were ideally suited for the FDNY’s standard tactic of quick vertical or horizontal ventilation, coordinated with a search, and a 1-3/4″ or 2-1/2″ line equipped with a smoothbore nozzle coming quickly behind to knock down the fire. These tactics, unfortunately, are being proven less effective, as the structures have remained the same but the contents have changed dramatically. The tests are a gigantic step in the right direction, and I applaud them.In addition, the newer homes and structures being built in the outer boroughs (like everywhere else in the country) are tending toward lightweight construction using engineered products and larger open spaces, rather than small compartments. These are fires the FDNY is ill-prepared to fight, and about which (hopefully) they will gain more information and adjust their tactics before there are too many more injuries and fatalities.
BH

The Navy doesn’t usually have to worry about steaming civilians with that tactic. They DO, however, need to worry about how much water they use to fight the fire.