We have had two outstanding debates over the past few months on the internet forums that explored how using the same water flow-rate and method of application (fog-pattern) might see both good and bad effects.
If you are directing a fog pattern into a fast-moving and intense fire at the outlet of a flow-path, compared to applying the same into the inlet of a flow-path your lpm/gpm may be effective or entirely non-effective.
The two circles on image 1 show how a fast moving flame-front can drag a third of your water droplets back out into the street without having impacted the fire in any way (solid circle no effect – dotted circle some effect). However, applying the same quantity of water into the base of a stair-shaft fire, using the natural air flow and buoyant effects of rising heat, can be very effective in suppressing large amounts of fire.
Working with a hand-line means trying to apply water most effectively, using the right flow-rate for the involved fire load but also being smart in how and where you apply it. Straight stream solid bore into the mouth of the dragon or a fog pattern into it’s tail!
It is also true that some fires require more water than others to gain early control.
+ Residential fires need less water than commercial fires
+ Commercial fires need less water than warehouse fires
+ Wind driven fires need more water (if you are heading into that flow-path)
+ The larger the windows in a building – the more water you may need for a developed fire
+ Greater amounts of water applied in the first ten minutes on scene may mean less time spent on scene overall in the later stages at large fires
+ If the construction elements (timber frame) become part of the involved fire load you probably need to increase your needed flow by two to four times!
Adequate firefighting water – you need this!