ADSN/WFLD
Hey Guys - firstly we need to define the term 'flashover'....and that isn't as straightforward as it seems - http://www.firetactics.com/FLASHOVER.htm
In simple terms a flashover is a heat-induced form of 'rapid fire progress' (NFPA) however, the transition is so closely linked with the phenomena of 'backdraft' that firefighters are often (usually) unable to define between the two.
There are many valid statements already on this thread....and some not so valid! Lets try and keep to the original poster's questions without entering into a standard smooth-bore v fog debate!
Smooth-bore .v. combination nozzle to (a) test the atmosphere for flashover and (b) use in flashover conditions?
In (a) you can use either to probe 'test' the heat in the overhead. If you cannot see or feel the heat in the overhead it is a good tactic to place a brief 'burst' (small amount of water) up there. If the overhead is super-heated or hiding a rollover above your heads then you will HEAR the sizzle and pop of the water as it converts to steam.
In (b) it has been proven in many many research projects that water applied in fog patterns will cool the overhead far more effectively than a straight stream of smooth-bore. If the fog pattern is 'pulsed' in controlled 'spurts' then there will be NO over-pressure or steam engulfing the nozzle crew and NO upsetting of the thermal balance http://www.firetactics.com/THERMAL%20BALANCE.htm
However, the TWO main points are this -
1. If you are in the fire compartment itself and it is not too large then flowing water of either stream (fog or smooth) will most likely prevent a heat-induced flashover.
2. Any venting action initiated either by firefighters or naturally occuring MAY cause a heat induced flashover.....be aware of that fact!
Finally, the 'pulsing' of fog patterns into super-heated fire gas formations in the overhead are FAR MORE LIKELY to 'inert' these dangerous gas layers than any smooth-bore stream, greatly reducing the potential for backdraft or smoke explosions.
and Blacksheep........I admire your efforts at trying out 'pulsing' tactics but would suggest you don't throw out these techniques too early! Many firefighters in the USA have undertaken extensive and in-depth research of the fog pulsing tactics and approved this method, particularly for flashover control. http://www.firetactics.com/AUSTIN-TEXAS.htm and http://www.firetactics.com/US-NAVY.htm are a couple of examples.
Stay safe
Hey Guys - firstly we need to define the term 'flashover'....and that isn't as straightforward as it seems - http://www.firetactics.com/FLASHOVER.htm
In simple terms a flashover is a heat-induced form of 'rapid fire progress' (NFPA) however, the transition is so closely linked with the phenomena of 'backdraft' that firefighters are often (usually) unable to define between the two.
There are many valid statements already on this thread....and some not so valid! Lets try and keep to the original poster's questions without entering into a standard smooth-bore v fog debate!
Smooth-bore .v. combination nozzle to (a) test the atmosphere for flashover and (b) use in flashover conditions?
In (a) you can use either to probe 'test' the heat in the overhead. If you cannot see or feel the heat in the overhead it is a good tactic to place a brief 'burst' (small amount of water) up there. If the overhead is super-heated or hiding a rollover above your heads then you will HEAR the sizzle and pop of the water as it converts to steam.
In (b) it has been proven in many many research projects that water applied in fog patterns will cool the overhead far more effectively than a straight stream of smooth-bore. If the fog pattern is 'pulsed' in controlled 'spurts' then there will be NO over-pressure or steam engulfing the nozzle crew and NO upsetting of the thermal balance http://www.firetactics.com/THERMAL%20BALANCE.htm
However, the TWO main points are this -
1. If you are in the fire compartment itself and it is not too large then flowing water of either stream (fog or smooth) will most likely prevent a heat-induced flashover.
2. Any venting action initiated either by firefighters or naturally occuring MAY cause a heat induced flashover.....be aware of that fact!
Finally, the 'pulsing' of fog patterns into super-heated fire gas formations in the overhead are FAR MORE LIKELY to 'inert' these dangerous gas layers than any smooth-bore stream, greatly reducing the potential for backdraft or smoke explosions.
and Blacksheep........I admire your efforts at trying out 'pulsing' tactics but would suggest you don't throw out these techniques too early! Many firefighters in the USA have undertaken extensive and in-depth research of the fog pulsing tactics and approved this method, particularly for flashover control. http://www.firetactics.com/AUSTIN-TEXAS.htm and http://www.firetactics.com/US-NAVY.htm are a couple of examples.
Stay safe
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