Playing with Fire

Playing with Fire

By Moe Collins, Captain Washington Township FD, Lucas County, Ohio

There’s been a lot of discussion in the fire service the past few years regarding using the “New Wave 3-D” fog attack to stop flashover. This tactic is much more popular in Europe and other parts of the world than it is here in the U.S. Here’s a video of training for this tactic from Australia. The theory behind this tactic is that pulses of water fog in the hot gas layer cools it down enough to stop flashover but maintain visibility.

http://www.youtube.com/watch?v=gUSrS26vP1g

My thought after watching this video is that it seems to be “playing” with the fire. Yes, the visibility is maintained but the same can be said for applying a straight or solid stream to the ceiling AND it has the same results: cooling the hot gasses to prevent flashover without disturbing the thermal layer plus the added benefit of the larger water droplets splattering off the ceiling and reaching the seat of the fire!

One of the main “benefits” of using a fog stream is the larger surface-to-mass ratio of all the tiny little droplets that make up a fog stream are converted to steam more quickly than the larger droplets of a solid stream from a smooth bore nozzle. In a sealed compartment, this expanding steam will cool and “smother” the fire. Lloyd Layman, the “Father of Fog Firefighting” adapted shipboard firefighting to structural firefighting in the late 1940’s.

As shown in testing at the Rockland County Fire Academy, a fog stream entrains huge quantities of air into the fire compartment (the highest their testing equipment would read was 2000 cubic feet per minute but they estimated the flows to be as high as 10,000 CFM!) Testing using a solid stream nozzle and a combination nozzle in the straight stream position showed entrained air flows of only 500-700 CFM.1 You can test this yourself on a drill night. Open the nozzle and stand close. Change the pattern from straight stream to narrow fog to wide fog. You can feel the breeze that’s created.

One of the most difficult things to accomplish on the fireground for our understaffed departments is timely ventilation. For most departments, “ventilation” is starting the PPV fan after the fire has been knocked down. We may call this “ventilation” but in reality it is simply smoke removal. If we don’t have the manpower (or the experience/training) to properly ventilate opposite the attack line, what is going to happen when upwards of 2,000 CFM of air is pushed in AND the small water droplets are turned to steam, where is it going to go? Most likely right back to the nozzleman but the hot steam and fire gases may also spread to other places inside the structure including areas where victims may be trapped.

http://www.youtube.com/watch?v=vkNFPWyidlc

Why “play” with fire? As shown in the video above, an attack line with an adequate flow, in a straight or solid stream will cool the fire gases below their ignition point and will maintain visibility and prevent steaming your attack crew and any occupants in the structure that don’t have the benefit of SCBA and bunker gear.

What’s an “adequate flow”? Stay tuned, brothers and sisters…

Let me know your thoughts & experiences on the 3-D Fog Attack or fog streams for interior firefighting in general in the comments. Be Safe but Be Aggressive!

1: “Nozzle Tests Prove Fireground Realities” Knapp, Pilsworth & Flately Fire Engineering Volume 157, Issue 2 http://www.fireengineering.com/articles/print/volume-157/issue-2/features/nozzle-tests-prove-fireground-realities-part-3.html