Firefighting tactics for shop fires in town centres – The Town Centre ‘Shop Fire’
Over the past few decades we have seen a greater use of plastic materials in our homes and workplaces and this has led to higher fire loads in nearly all building environments. We have also experienced greater uses of natural light with larger windows in some cases, and an increase in glass shop front dimensions. With these factors coupled together, we are now seeing greater intensity in the fires we respond to as increasing ventilation profiles feeding higher fire loads become commonplace.
In fact our town centre shops have gone through a phase of redevelopment during the past twenty years that has resulted in greater floor space, far deeper shops going back as much as thirty metres and floor to ceiling window glass at the front of the units. We are now seeing a sudden trend in serious town centre shop fires that escalate far beyond the original shop unit to involve upper floor levels (sometimes residential) and surrounding buildings.
We must therefore address our tactics and optimise the way we apply water, or alternative means of extinguishing media, when suppressing or holding fires, in order to place greater control over fast developing fires from the outset.
THE TOWN CENTRE SHOP PROBLEM
The problem with town centre shop fires lies in the fact that they are now so heavily loaded with combustibles, ranging from shoes, to sports equipment and clothing, to paper goods and card shops that demonstrate an elongated floor space with a large glass opening at the front that generally fails early in a developing fire. However, the actual opening to floor space factor (Av / Af) demonstrates a very low ventilation factor for a high fire load.
What this means is that when a fire occurs, the air supply is initially ventilation limited and the fire load will burn for a very long period (at around 15 MW heat release rate) in an area that is difficult to reach from the street using exterior streams.
However, the fire intensity in the shop creates a funnel of heat heading towards the front and entry is often difficult for firefighters due to untenable conditions. In effect, such fires burn for a very long time and may well breach fire resisting partitions and spread both horizontally and vertically into adjacent areas. Unfortunately, it is rare to find sprinkler protected shop units in town centre developments outside of covered shopping centres.
FIREFIGHTING TACTICS AT TOWN CENTRE SHOP FIRES
In some cases, particularly where the fire is located in the front section of the shop, a high-flow stream of water or CAFS is required to gain rapid knockdown at an early stage of fire development as fire and heavy hot smoke breaches the front windows. At this point the firefighter is faced with applying a quantity of water that will extinguish a major part of the fire whilst maintaining a constant supply of water as the water tank heads towards dry.
If there is an 1800 litre tank on-board this will run dry within 3.5 minutes unless an immediate hydrant or water supply is located. A second fire engine may be used to augment the supply at this point, if immediately on-scene.
Tactical options at fast developing town centre shop fires:
1 One or two high pressure hose-reels from the street in an attempt to ‘hold’ fire spread
A hydrant should be available before the water tank runs dry
2 A main 500 L/min jet applied from the street using tank water and then hydrant 3.5 minutes before the water tank runs dry
3 A portable monitor (1500 L/min) applied from the street using tank water (BLITZ attack)
Just over one minute before the water tank runs dry
Table 7.1: Tactical options for fast developing town centre shop fires
One will ponder over these three options but they are generally the three tactics used where a shop front is spewing large amounts of heavy smoke and fire on arrival.
It is however clear that very few firefighters or fire commanders will choose option 3 (BLITZ) although this is quite often the best and only way to deal with such fires.
There are countless videos on social media of firefighters attempting to control intense shop-front fires immediately following arrival with one and even two jets, to no avail.
The decision to use option 3 will of course depend on (a) equipment availability and stowage; (b) time to support engines arriving on-scene; (c) location of and access to nearest hydrants or water supplies, and; (d) fire conditions as they present. However, this scenario is certainly one to be planned for and prepared for. Is your crew actually prepared to deliver 1000–1500 L/min in one quick hit?
It isn’t that long ago that we had roof-mounted monitors on our fire engines to deal with exactly this kind of situation.
What does this mean to the Firefighter?
There is a national trend in the UK where town-centre shops have become deeper (longer) following redevelopment over the past two decades and the fire loads have increased dramatically in-line with plastic content. Add to this the larger windows than these shops used to have, sometimes with full-width glass, and we have a recipe for very intense long duration fires that are difficult to reach with firefighting streams.
What generally happens is that 2–3 firefighting jets are unable to achieve knockdown from the street as the fire reaches structural boundaries to spread vertically and horizontally back and sideways, involving all the surrounding buildings. Again, common roof voids add to the problems and in some cases, firefighting may be delayed due to the typical ‘shop and dwellings’ construction that places a life risk directly above. Tactical options may need to address these fires in ways that are not commonplace to UK firefighters these days.
In fact, going back to WW2 firefighting tactics using high-flow >1500 L/min external streams immediately on arrival may be required.
This will require some elements of pre-planning in relation to the location of adequate hydrant grids and the provision of portable monitors fed by a single 90mm hose-line.
Article written by Paul Grimwood from Euro Firefighter 2