3D Water-Fog 'Pulsing' Tactics

[Paul Grimwood]

In the early part of February 2001 the Austin Fire Department in Texas USA completed 146 live training burns in acquired structures and evaluated the 3D water-fog approach in every situation. Over 500 students employed this form of fire attack and noted that the application of 'pulsing' water-fog droplets into the super-heated fire gases 'worked on the great majority of fires'

The 'new-wave' applications developed throughout europe since the 1980s were particularly effective when traversing the approach route to fire-involved compartments. The improvements in visibility and maintaining thermal balance when compared to smooth-bore attack was particularly outstanding.

It was noted that on a few occasions the fire would grow so rapidly that no amount of nozzle 'pulsing' would control it and on these occasions even a smooth-bore application failed to reduce the fire's intensity, causing firefighters to retreat

One Austin Fire Officer stated - 'I believe the 3D attack method worked very well and was the method of choice in the vast majority of the fires we encountered in the training and are likely to encounter in the field. The use of 3D water-fog pulsing streams is the safest and most effective method compared to other applications although it is not suited to all situations. We are now teaching our firefighters these techniques'.


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[Company40]

How much water do Europeans flow in their handlines when using this technique. I think that I once read that low flow rates are used.

Also Paul, do you have any statistics about the lowered risk of firefighters being caught and hurt/dying in flashovers. I was wondering if European countries have found a drastic reduction in flashover deaths since the introduction of this technique.

[Paul Grimwood]

Hi Company 40,

The optimum flow-rates for applying these 'pulsing' techniques are variable and depend on several factors including the objective (gas-cooling or flame extinction as gases are burning off; size of compartment and involved fire load etc). In the UK we have used flow-rates as low as 10 gpm US (yes) during training evolutions in containers to cool the fire gases emitting off an escalating 1 MW fire although this flow requirement is nearer 40 gpm for operational use in contained one-room residential fires (gas cooling). This water is supplied through 3/4" high-pressure (500psi) hosereel (booster) lines which are common in UK.

However, I know in Sweden they prefer flows in excess of 80 gpm for this style of application and Australia resort to a similar flow as a minimum, all varying upwards depending on objectives and size of fire.

The US Navy utilise these techniques with flows in excess of 95 gpm whilst the Texas firefighters involved in the extensive tests were using hand-lines supplying 125 gpm.

These techniques may be applied safely and effectively with a variable flow-rate although I personally prefer the higher flow-rates for 'real' firefighting. I would say their is a general trend towards selectable-flow combination style nozzles across the world where the nozzle operator is able to choose from a variety of flow patterns ranging from 30 gpm for small compartment gas-cooling fog applications to the 140 gpm straight stream application where needed.

Trained operators know when and how to utilise the varying water applications - fog or straight stream - to the best effect.

[Paul Grimwood]

Whilst I have no official statistics in relation to injury reductions where firefighters are concerned I can say that I went to a Swedish training seminar a couple of years back where the lecturer stated that NO Swedish firefighters have lost their lives to flashover since the late 1980s when this style of approach became commonplace. Before this their life loss statistics (through rapid fire propagation) were one of the highest in the world. Here in the UK such losses have drastically reduced as firefighters become more aware of how fire gases evolve and transport through structures. The training itself demonstrates the presence of invisible gas layers - something firefighters have failed to realise in the past, this is a good thing on its own.

Pulsing fog tactics will not completely remove the fireground hazards associated with flashover/backdraft but experience is demonstrating that if correctly utilised, inline with safe tactical venting practice, the average structure fire is being handled with a greater element of safety and control by employing such an approach.

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[Dalmatian90]

Paul...

Question of semantics...I think it's a typo but it is a head scratcher:

It was noted that on a few occasions the fire would grow so rapidly that no amount of nozzle 'pulsing' would control it and on these occasions even a smooth-bore application failed to reduce the fire's intensity, causing firefighters to retreat

Where they using smooth-bores including for the 3-D
or
Did you mean Straight-stream from a combo nozzle
or
Where there two hoselines and nozzles in use?

By the way, Paul's book is an interesting read. According to my Dalmatians it tasted even better. Grrrrr

[chief1001]

I noticed you siad " Good tactical venting practices", Im glad you mentioned it because
if you failed to vent before you applied this practice, a great deal of steam is generated with no where to go. Boy does it suck getting a steam bath this way

[KEA]

Paul,

/it was noted that on a few occasions the fire would grow so rapidly that no amount of nozzle 'pulsing' would control it and on these occasions even a smooth-bore application failed to reduce the fire's intensity, causing firefighters to retreat/

I would believe that if this were the case, regardless of the nozzle or technique being used, the problem was lack of application rate for the fire!

If making that long hallway using this technique gets me to the fire safe I MUST still ensure that I have the proper applicaiton rate (GPM or LPM) to put the fire out.

The challenge I have with trying to use tactics that maximize the water droplets effectiveness is that more often than not we sacrifice our application rate.

Every fire is different and will do different things from the beginning to the end. What ever tactic you choose for suppression I would beg that you couple that tactic with the ability to have a high application rate!

Just my opinion, which is not intended to sell anything, buy anything, or bash anyone else or their way of thinking.

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Kirk Allen
First Strike Technologies, Inc

[This message has been edited by KEA (edited 05-20-2001).]

[Paul Grimwood]

Hey there Matt,

no typo but to be honest, I understand they were using both smooth-bore and straight streams to compare, although in this situation the report I have uses 'straight stream' - ie; neither water-fog or straight stream was able to handle the fire intensification. But take note - this is down to involved fire load and availability of air rather than application style. If you are dealing with a 5MW ventilation controlled fire ( a real worker) (as an example) then you need to flow enough water to counter the fire and heat conditions - if that isn't available at the nozzle in the first place then you may be forced to retreat.

Respect fully what you are saying chief but tactical venting is NOT a requirement inline with 3D water-fog applications - if there is excessive steam production then it is because the nozzle operators are mis-applying the 'pulses' or the nozzle in use is flowing too much water whilst attempting to cool the gas layers. I merely mentioned 'tactical venting' as a way of controlling an intensifying fire - by 'closing' the building back down! ie; reducing air-flows into the structure until enough water is made available to the attack team - the two go hand in hand - 'control' is the key!

Hey Matt - if the Dalmations like the taste of my books perhaps I might get more success selling them in cans?! ;-))



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[Paul Grimwood]

Couldn't agree more Kirk mate! Application rate is the key to extinguishment. I also appreciate fully what you say inline with having that high-flow available when you reach the end of that long hall-way.

However, its a case of matching flow requirements with each situation - if the fire involves one room (most of 'em do) then a 150 gpm line will handle the normal residential fire load and a combo nozzle with selectable settings will allow gas cooling on the approach.

However, if you have a major fire front with several rooms or the whole structure involved then its time for the 'big guns'!!

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[Company40]

No Swedish firefighters have died from flashover since instituing these tactics. That's a very impressive statement. It's a shame more countries can't make the same claim.

40 GPM seems to be pretty low flow rate for entering a structure fire. The only time I have ever used such a line is when fighting a brush fire. I would be more comfortable flowing over 100 GPM like the US Navy.

I guess if you face a fire that requires a large application rate, the fire has already flashed over. At this point, you have no reason to pulse the nozzle in an effort to prevent flash over. Now your primary concern is flowing as much water as possible on the fire.

[Paul Grimwood]

Don't forget Co.40 - a 40gpm line working at 500psi is a different tool compared to the 'trash' line flowing the 40gpm at less than 1/5th of the pressure. These high-pressure boosters are excellent tools for pulsing superheated gas layers.

However, I agree with the points you raise.

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