Optimising Fire Service Response

In the 1970s, I worked on detachment alongside firefighters in New York City’s busy South Bronx area, observing how firemen there were applying greater amounts of firefighting water in their hose-streams than London were. In fact, London and UK firefighters deliver even lesser amounts (L/min per square metre) now than they did back then although FDNY are still equipped to deliver the same as in the 1970s. A study I undertook back in the early part of the millennium [p198 ‘EuroFirefighter’ 2008] demonstrated that a large percentage of UK FRS’s were falling far short of the water delivery at building fires than they actually believed. The research showed 89% of the 58 UK FRS’s were showing short falls in believed target flows and in some cases were only achieving as little as 16% of their assumed target flow rate. Firefighters were further grossly under-estimating the flows (L/min) in tall building fires when using rising fire mains. One of the biggest problems of the period was low pressures existing at height (Less then 4 bars) where some automatic branches/nozzles required at least 6 bars at the nozzle to function/flow effectively.

There is a vast amount of research undertaken by the Fire Research Station in the 1970s and earlier in collaboration with Universities in Germany and the USA on which rising fire mains were designed and this showed a minimum flow rate of 450 L/min should be available on a single hose-line for flat (apartment) fires. This research still holds true today and yet so often, I recorded flows of around 200 L/min or less on the first hose-line. At one test we received just 80 L/min for a mainline automatic branch at the 20th floor level.

The popularity of Swedish compartment firefighting methods (first introduced into the UK by this author in 1991) suddenly saw a need to become more familiar with fire dynamics and practical training demonstrators concentrated on fire behaviour as well as developing techniques associated with ‘gas phase’ firefighting, even though in real fires it is the fuel phase that is the predominant fire load involved. Work in Germany suggested that the heat extraction of a compartment fire is broadly taken from two thirds fuel phase of the involved fire load, compared to one third the gas phase. In contrast, for the past twenty years we have biased our training and equipped our firefighters almost entirely towards dealing with the gas phase fire load. In fact, it is flow rate and not droplet size that is the predominant factor in determining the effectiveness of suppressive capacity. The reason for this is it is it is extremely difficult to train and equip UK firefighters to achieve optimum impact, in the time and budgets we have, in order to be highly effective when concentrating our bias on gas phase firefighting.

Study of over 6,000 working fires in the UK 2009-2016

This study undertaken by Kent FRS, in what we termed our ‘capability review’, showed us that in comparison to a busy Metro Fire Service (who collaborated in presenting flow metered data from the fireground), we were falling short in terms of an increased level of building fire damage in our response area. This was inevitably because the Metro fire stations were spaced more closely together, making their attendance times far quicker. In fact, the later we arrived at a fire the more water we needed to use to achieve effective suppression and the greater number of jets we were using compared to the Metro FRS. In fact, we used twice as many jets as the Metro did per fire but still delivered the same amount in total, at an average of around 12 L/min/m2. Our total resource needs were much higher than the Metro FRS for the same fire. We were averaging 39m2 fire damage per fire compared to Metro’s 30m2. That works out to almost an additional room in each five roomed flat, or 25% greater in fire damaged area! We evaluated our firefighting tactics and response from a fire dynamics point of view and looked at how a fire growth curve might evolve over time within a range of fire compartments of differing dimensions and assumed that if we delivered a much greater firefighting water flow rate at the point of arrival we may catch up with and overpower the fire growth. More water than the Metro FRS were delivering but at a slightly later stage in the fire development. It made sense.

We upgraded our hose reels from 19mm to 22mm to double the flow rate. We brought in 51mm attack hose to replace some 45mm and added 22mm smooth-bore nozzles and appliance flow meters across the fleet. The idea was to hit the fire with more water than we had been doing at a later stage of arrival, compared to the Metro FRS. It worked! We saved the customer base ￡￡￡ thousands in fire damage but there were undoubtedly some increases in water damage. There must be a trade-off here. People don’t ‘drown’ at fires they die from fire, heat and smoke. Fire damage caused by excess water is more easily addressed through insurance claims and we had to place firefighter safety at the forefront of our strategy. If our firefighters are arriving later than a Metro response, then they could be facing greater exposure to risk. In almost doubling our applied water flow rate in many respects, we had dramatically reduced our ‘average area of fire damage per fire (to 21m2) and increased the fire containment data (confined to compartment of origin). It has always been a career long study of mine, researching firefighting water flow rates, that has provided the foundation for National Operational Guidance, UK Water Firefighting Water (DFC 2023) and national firefighting access design standards (BS PD 7974-5). Looking back to those early years with the South Bronx firefighters in New York and the personal introduction and development of Swedish fog tactics in the UK that followed, it is now more clear to me how we are able to optimise our response resources, training and equipment budgets whilst increasing the safety for our firefighters in order to make the greatest impact in reducing fire damage in building fires.