Fire and Rescue Service Wildfire Operational Guidance

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8B8 Fire Suppression Tactics

Overview of FRS Wildfire Suppression Tactics

8B8.01 There are two main methods used to suppress wildfire, these are:

Direct Attack - where personnel and resources work at, or very close to, the burning edge of the fire. Firefighting crews aggressively attack the fire either by applying water or extinguishing the fire using 'hand tools' and 'beaters'.

Indirect Attack - this method involves applying suppression tactics that take place away from the burning edge of the fire. Either by using control lines to contain fire spread, or the proactive use of fire as a suppression tool.

8B8.02 Although some FRSs have a limited knowledge of indirect attack methods, few have incorporated these fully into their systems of work. Fire is a very effective suppression tool and is used extensively in Europe, the USA and Australasia. Unfortunately it is not widely used in the UK and only a few FRSs have developed the skills necessary to apply it operationally.

8B8.03 Helicopters and fixed-wing aircraft can also use direct and indirect attack methods. Water drops, directly applied onto the fire, are an example of direct aerial attack; while drops made to strengthen or create fire breaks some distance away from the fire's edge are an indirect attack technique.

8B8.04 Aerial attack and suppression tactics are dealt with in more detail in Part B9.

Fire and Rescue Tactics

8B8.05 Direct attack is an effective method of suppression, and one that can be used with great success, but it is a technique that has limitations and is more successful when used on fires with an intensity producing a flame length of below 1.5m.

8B8.06 If a FRS's tactical fire fighting methodology is limited to direct attack, it becomes increasingly difficult to gain control of a fire as the intensity increases. This can lead to a situation where more and more resources are being committed with little effect. Fire behaviour at such fires may increase the levels of risk to a point where they become dangerous.

8B8.07 The use of alternative 'indirect attack methods', can prove to be more effective than direct attack methods and can often be applied with a greater emphasis on personnel safety. The indirect attack methods described in this guidance were developed by agencies from outside the UK, (most from a land management and non FRS background) and they are specific to wildfire. Once understood, they can be introduced and used by FRSs with confidence.

The successful application of these tactics will depend on FRSs acquiring new skills and adapting their firefighting approach.

Direct Attack

8B8.08 The emphasis in a direct attack focuses on a fire being fought aggressively by personnel at close quarters at the fire edge. This attack can be launched by crews using hand tools, or crews equipped with a water delivery system or a combination of both.

8B8.09 It is always advisable that water, or some other form of extinguishing media, is available when undertaking a direct attack. FRSs in the UK are already familiar with, and competent in the use of, open and closed circuit water relays, water ferrying and the deployment of High Volume Pumps (HVPs) when dealing with large spatial vegetation fires.

8B8.10 Direct attack methods can be extremely successful when deployed against fires of low (flame length up to 0.5m) and low/medium intensity (flame length up to a maximum of 1.5m). Fires that demonstrate flame lengths above 1.5m become progressively more difficult and dangerous to control. Although the application of water via pressurised systems may still have some success on fires above this threshold, personnel working with hand tools such as beaters should be withdrawn until flame length is reduced.

Hand Tool Crews

8B8.11 These are made up of personnel who are equipped to fight a fire using techniques, which utilise hand tools and portable firefighting equipment. Hand tool crews should be equipped with fire fighting equipment such as beaters and knapsack sprayers. They can also use mattocks, spades, saws and other equipment specific to control line construction.

8B8.12 Hand tool crews should consist of an appropriate number of personnel specific to the task. They can include trained personnel drawn from the land management sector operating under FRS supervision and control.

8B8.13 Depending upon the size of the wildfire event and the tactics deployed by the Incident Commander, it is often more effective to utilise larger crews consisting of between six and 12 personnel.

Water Attack Crews

8B8.14 These are crews that have the capability to launch a pressurised water attack on a fire. This could include the use of fire appliances, portable pumps and other assets, such as high pressure water fogging units.

Attacking the Fire

8B8.15 A wildfire, under normal circumstances, should always be attacked from the rear and where possible from an area that has already been burnt. This prevents personnel from being placed in front of a fire in unburnt fuel, which can be particularly dangerous.

8B8.16 The timing of an attack is also important, changes to alignment and fuels will result in different fire intensities. Attacks should be made at times and places where the fires are burning with lower intensities. For example, if a fire is burning upslope it might be prudent to delay any attack on the head part of a fire until it reaches the top of the slope, where its intensity will fall.

Working from an Anchor Point

8B8.17 It is crucially important that suppression tactics are begun from secure locations on the landscape, strong enough to act as barriers to fire spread. The commencement of operations from these 'Anchor Points' ensures that the fire cannot escape from the containment area threatening the success of the operation or the safety of personnel. If necessary, Anchor Points should be strengthened, or even created, by the use of hand tools or machinery.

8B8.18 Crews should normally work from an Anchor Point along the flank or flanks of the fire towards the head.

Working from the Black

8B8.19 Whenever possible, it is good practise to work from within the burnt area or what is termed to be 'the black'. Working from 'the black' can provide crews with some security as they are working from behind the fire, in an area that has already been burnt. When doing so, it is still important to understand that the fuel in the black area may not be completely burnt, and should the fire change its direction; the remaining fuel may support a second burn.

8B8.20 Nevertheless, the black area is usually the safest place to work from and offers some protection to FRS personnel from the effects of heat and smoke.

Fig. B8.1 Wildfire hand tool crew supported by a pressurised water system using the track as an Anchor Point and attacking the flank from within the black

Fig. B8.1 Wildfire hand tool crew supported by a pressurised water system using the track as an Anchor Point and attacking the flank from within the black

Responding to Changes in Fire Behaviour

8B8.21 As wildfire behaviour is changeable, it is important that crews using a direct attack maintain a flexible approach to the tactics being used. As a wildfire progresses across a landscape there will invariably be changes in fire behaviour. Advantage should be taken of situations where a fire is burning in different fuel types at lower intensities, but in areas of higher intensity tactics may have to be modified, sometimes this may mean that indirect tactics are adopted.

The Use of Water at a Wildfire

8B8.22 Water remains the most effective method of extinguishing wildfire, especially when supplies are plentiful and it can be applied via a pressurised system such as a fire service pump. Most FRS firefighting pumps are mounted on vehicles that have limited capability to operate off-road or away from level, and hard, surfaces. These limitations often result in assets and resources being unable to be deployed at, or even near to, the scene of operations.

8B8.23 Where there is a lack of suitable and sufficient water supplies in rural areas. FRSs should make arrangements to identify open water supplies as part of their local pre-planning arrangements.

8B8.24 There may be problems in moving and supplying water to the scene of operations. Where water supplies are limited then it should be used sparingly. Under certain circumstances High Volume Pumps (HVPs) can be utilised to move large volumes of water to and around a fire ground. FRSs should assess the suitability of HVP deployment within their local pre-planning arrangements.

Whenever HVPs are deployed, early consideration should be given to the potential requirement for an HVP Instructor or Subject Matter Advisor to attend.

8B8.25 Water has its limitations, and at very intense fires its application may not substantially reduce the intensity and rate of spread of a fire, to a point where it allows the fire to be contained or extinguished.

The Application of Water

8B8.26 The purpose of applying water as the main suppression method is to completely extinguish the fire, as with structural firefighting techniques, which is best achieved by applying the water to the base of the flame. This is particularly relevant in wildfire situations where maximum efficiency is required from the use of water.

8B8.27 Operatives should take up a safe position, as close to the fire as possible. As they work along the fire front extinguishing the flames, they should constantly check that all hot spots are extinguished. If any are left burning the fire may reignite and the resulting fire may place the water attack crew in danger.

Water should normally be applied using a spray or fog. Jets should only be used:

  • To cool a hot fire to enable personnel to get closer to the fire front
  • If more penetration is required
  • Where water has to be applied from a greater distance

It is good practise for a hand tool crew to work in tandem with the water attack crew; they should extinguish or dig out hot spots as the water attack progresses along the fire front.

Different Methods of Direct Attack

8B8.28 Attacks should be based on expected fire behaviour and full advantage should be taken of when a fire is demonstrating low intensities. It is advantageous to extinguish the tail part of a fire as soon as possible, this can secure an anchor point to work from and eliminates the possibility of it changing its alignment and increasing in intensity.

Flank Attack

8B8.29 Fire behaviour is normally less intense on the flanks; it is normally good practice to attack the fire from behind, progressing along the flank towards the head.

Fig. B8.2 In this illustration the crew is attacking the left flank and working in the pre-burnt area

Fig. B8.2 In this illustration the crew is attacking the left flank and working in the pre-burnt area

Fig. B8.3 In the illustration above two crews are attacking both flanks of the fire; this is referred to as a ‘pinching attack’. Working from the tail of the fire the crews take advantage of the black area where the fuel has already been burnt

Fig. B8.3 In the illustration above two crews are attacking both flanks of the fire; this is referred to as a 'pinching attack'. Working from the tail of the fire the crews take advantage of the black area where the fuel has already been burnt

Head Attack

8B8.30 Unless a fire is of low intensity, the head part of a fire should normally only be attacked once the flanks have been extinguished. This is partly because the head fire gains some support from the flank fires and, once these have been extinguished, fire intensity at the head will normally reduce. Direct attack against a head fire is normally only successful on lower intensity fires. It may be dangerous to attack a head fire from the front, particularly when personnel are placed in unburnt vegetation.

Fig. B8.4 Crew working from the back using water to attack a head fire

Fig. B8.4 Crew working from the back using water to attack a head fire

This illustration shows a water attack crew extinguishing the head of the fire from the rear. Due to the head fire having the greatest fire intensity and rate of spread, head attack is normally only possible at low intensity fires and extreme care should be taken when employing this tactic.

The Use of Water as a Secondary Method of Suppression

8B8.31 Where water supplies are scarce or when FRS vehicles are unable to gain access to the scene of operations, hand crews may have to carry out an attack using hand tools and knapsack sprayers. Wherever possible crews should be supported by 'All Terrain Vehicles' (ATVs) that carry portable firefighting systems or are equipped to carry water supplies that can be used to refill knapsack sprayers.

Photo B8.1 A photograph of a wildfire vehicle equipped with a fogging unit which can provide water support to hand crews

Photo B8.1 A photograph of a wildfire vehicle equipped with a fogging unit which can provide water support to hand crews

8B8.32 A hand crew should consist of sufficient numbers to meet the requirements of the task. Where water supplies are limited the water should be used to lower the fire intensity rather than extinguish the fire. The application of very small amounts of water will reduce flame length and the heat generated by the fire. The application of water in this way will significantly increase the duration of the water supply. Personnel using fire beaters or other hand tools positioned close to the fire front are then able to work more effectively, and are protected from the worst effects of the heat and smoke generated by the fire. Whenever appropriate, and subject to the operating procedures within the FRS, the use of water additives should be considered to increase the effectiveness of the water application.

The Use of Water with Water Additives

8B8.33 There are a number of chemical substances that can increase the effectiveness of water used at a wildfire. Where water supplies are limited, the use of additives will significantly increase its effectiveness. FRSs who are considering using water additives, should ensure that they undertake appropriate research to determine the most suitable product for their local wildfire risk and that any impact to the environment is acceptable and complies with current FRS guidance.

Water additives fall into three main categories:

Wetting Agents - are substances that increase the ability of water to penetrate and spread over a surface. Wetting agents are very effective when applied directly onto the flame or during the mop-up phase.

Retardants - can be applied onto vegetation to create a fire break or can be applied directly onto the fire. Many of these types of substances have chemicals that limit combustion and fire spread even when the application has dried out.

Gels - can be applied as a firefighting medium or used as a fire break; these types of substances thicken the water allowing the application to stick to the surface and remain in situ for much longer.

Photo B8.2 A retardant drop

Photo B8.2 A retardant drop

8B8.34 The use of wetting agents, or 'Class A' foams, in wildfire situations is by no means new, although there has not been a long tradition of doing so in the UK. Wetting agents are generally mixtures of synthetic hydrocarbon detergents designed to lower the surface tension of the applied water. This has two main effects. First, the projected water is better able to split into smaller droplets which vastly increases the surface area per unit of water, making the application more efficient and effective. Secondly, a weak detergent solution will soak into the wildfire fuel much better than plain water which, because of its higher surface tension, can have a tendency to 'bounce off' and run unsatisfactorily to ground.

8B8.35 Wetting agent concentrates are highly polluting in the aquatic environment. Detergents are both acutely toxic to aquatic organisms and oxygen depleting owing to their very high Biochemical Oxygen Demands (BOD).[1] It is important to ensure that if foam or wetting agents are to be applied to a wildfire, that it is definitely a Class A product. Film forming Class B products, whether protein (as in FP or FFFP) or synthetic AFFF should not be used. Class B foams are designed to flow over a flat liquid surface and seal it so removing the oxygen; they do not adhere well to the vertical surfaces or convoluted shapes that would be present in the wildfire environment. In spite of containing detergents, the presence of the film forming ingredients virtually prevents the foam solution from soaking into the wildfire fuel.

Indirect Attack Methods

8B8.36 These tactics should be applied at higher intensity fires, where firefighting close to the fire's edge may be more dangerous. As the name suggests, Indirect attack is where firefighting techniques are applied 'indirectly' or away from the fire's edge. The purpose is normally to contain a fire within a chosen boundary. Due to the fact that these techniques are applied some distance from the fire front, they can often be a much safer way of fighting a fire.

There are three principal methods of indirect attack and these are:

  • The use of control lines
  • Parallel Attack
  • The use of fire as a tool

The Use of Control Lines

The Use of Control Lines 8B8.37 The principal indirect attack method employed at most wildfires is likely to be the use of fire breaks and what are termed to be 'control lines'. Control lines can be constructed manually, mechanically or by the application of water or retardants which are termed to be 'wet lines'. Existing features of terrain can also be used; roads, tracks, rivers or streams, even outcrops of rocks or areas of vegetation that will not support combustion can all be used to prevent fire spread.

8B8.38 Control lines are constructed to form a barrier that will prevent fire spread. This can be to specifically impede the spread of the wildfire, or to create a safe strip from which to start firefighting operations.

8B8.39 Manual or mechanically created control lines must be dug down into mineral earth and all fuel must be removed, and they must be wide enough to prevent the fire from jumping over into fuel on the far side. Normally this should be two and a half times the length of the fire's flame length.

8B8.40 The edge of the control line facing the fire should be termed to be the 'Inner edge' and the edge facing away from the fire should be referred to as the 'Outer edge'.

8B8.41 A fire that is 'spotting' (creating additional fires due to flying brands and embers) can create secondary ignitions that can ignite fuel in front of the main fire; these can easily jump over into the fuel beyond the outer edge of the control line. Therefore, before constructing a control line, consideration should be given to the fuel types that the control line is being constructed through, and whether these are likely to support spotting behaviour.

Planning the Construction of a Control Line

8B8.42 Before commencing the construction of a control line, a plan should be made, and it is important to consider the following points:

  • Always ensure that the control line is started from a strong anchor point. A control line that does not completely close in a fire may allow fire to spread around it.
  • Plan to take the shortest route and keep the line as straight as possible. Sharp bends will create weak points where the fire may be able to penetrate the line. When a change of direction is made, ensure that bends are gradual. If bends have to be more severe consider broadening the width of the control line at these points.
  • Take full advantage of existing features of terrain and natural or man-made features that will prevent fire spread.
  • Where possible control lines should be constructed in fuels that produce low fire intensities.
  • Plan the route to pass through fuel and vegetation that is easier to work in. For example, a longer route through grass may be significantly quicker to build than a shorter route through scrubland.
  • Build the line as close to the fire as possible, but take into consideration the rate of fire spread. Ensure that there is enough time to complete the control line before the fire reaches it. By keeping close to the fire, crews may be able to use the black area as a safety zone.
  • Constructing a control line on a slope above a fire is extremely hazardous and, because of the likely increase in fire intensity, is potentially ineffective. Consider routing lines along the base of slopes or on the reverse side.
  • Constructing a control line in front of the head fire is extremely hazardous. Ensure that crews are positioned a safe distance from the fire front and that their escape routes and safety zones cannot be compromised if the fire changes its behaviour.
  • When constructing a control line on a slope below a fire, it should be constructed in such a way that it prevents any rolling materials passing over it and into unburnt fuel on the outer side.
  • Plan what threat there is to the line being penetrated. Flame length, wind strength, radiant heat, fuel type, ground fuels such as roots or buried branches, rolling fire debris etc. must all be considered.
  • Control lines can be strengthened by wetting the surrounding fuel, covering it with some form of fire retardant, or using fire to remove the fuel completely.
  • Due to the arduous nature of control line construction consideration should always be given to the welfare of personnel, particularly with regard to maintaining hydration and providing regular rest intervals/reliefs.

Manually-constructed Control Lines

8B8.43 The manual construction of control lines requires a great deal of effort and can be labour intensive. Nevertheless with tools appropriate to the vegetation and soil types they can be established relatively quickly. The ease at which a control line can be constructed will depend on a number of factors including:

  • The vegetation type
  • The terrain
  • The tools available
  • The soil type
  • Training and crew work
  • The time available
  • The availability of sufficient numbers of personnel

Photo B8.3 A Catch Trench on a slope and constructed to prevent burning material from rolling down slope

Photo B8.3 A Catch Trench on a slope and constructed to prevent burning material from rolling down slope

8B8.44 Control lines can be used on fires of lower intensity as well as those of higher intensity. It may be more beneficial to construct a control line than commit crews to the edge of a fire where they may have to work in heat and smoke.

Hand Tools

8B8.45 All personnel will require training in the safe and effective use of tools that are used in the construction of control line. The tools required will vary depending mainly on vegetation and soil types, the following are only examples of the many types available:

Hand Tools

Progressive Control Line Construction

8B8.46 This guidance recommends that the 'progressive method' of control line construction is used. This is a systematic technique that involves each member of a crew performing a particular task. It is a system of work that maintains a safe space for personnel to work in and ensures that personnel are not over worked.

8B8.47 Under normal circumstances, a hand crew building a control line should consist of about ten members with the crew leader taking on the role of crew lookout. If the crew is not able to observe the fire continuously a tactical lookout should also be appointed and take a position from where they can observe both the crew and the fire.

Roles of Crew Members

(a) Pathfinder(s)

8B8.48 The first member of the crew should identify the best route for the line to take through the vegetation. When necessary personnel operating as pathfinders should be equipped with a mechanical tool such as a chain saw or brush cutter so this can be used to remove larger pieces of vegetation. If appropriate additional crew members can assist by removing any cuttings, branches or logs. All fuel removed should be placed on the outer side of the control line; this will prevent a fire increasing its intensity on the inner side as it approaches the control line.

The rate, at which the crew makes progress, depends on the speed that the lead members can clear a path through the vegetation.

(b) Edge cutters

8B8.49 Following the line chosen by the pathfinder(s), two members of the crew cut the edges of the control line into the soil. The first forming one edge and the other, following at least 3 metres behind, cuts the second edge. The width between the two edges of the control line will vary, but must be the minimum required to prevent fire spread.

(c) Diggers

8B8.50 Next in line are the diggers; these operate at least 3 metres apart and progress along the line digging/raking out the fuel between the edges that have already been cut. Care should be taken to place all debris on the outer-side of the control line.

8B8.51 Fuel is removed in blocks. The size of block depends on the number of personnel available. Each of the diggers clear only a section of the block before progressing along the line where they dig out another section from the next block. Fuel from each block is progressively cleared until the last digger cuts the final section which must remove the last of the fuel. For maximum efficiency and safety, only one digger should be working in a block at any one time.

Photo B8.4 Showing each digger working a separate block

Photo B8.4 Showing each digger working a separate block

(d) Tail Crew

8B8.52 The last members of the crew clean the line by removing any remaining or missed fuel, making sure that all of the debris is placed on the outer side of the control line.

Fig. B8.5 Progressive control line construction

Fig. B8.5 Progressive control line construction

8B8.53 This illustration shows a crew using the progressive method. Two crew members cut the line to the required width while the rest of the crew follow on behind. Each removes a single strip from a block before moving on to the next. Working in sequence each member clears their designated strip until the last of the fuel is removed.

Photo B8.5 Showing diggers maintaining a safe distance apart whilst clearing a single strip from each block

Photo B8.5 Showing diggers maintaining a safe distance apart whilst clearing a single strip from each block

8B8.54 Using this system of work, each person does an equal amount of work and has a short rest while moving between blocks. Personnel are only allowed to move forward once the person preceding them has completed their cut. This ensures that a safe distance is maintained between personnel and that the crew works to the physical capacity of its members.

Mechanically-constructed Control Lines

8B8.55 The construction of control lines using machinery depends on the availability of suitable equipment and operators. Therefore it is crucially important that FRSs engage with partners and make the necessary arrangements to ensure that this type of equipment is available. The engagement with both the public and private sector may provide access to machinery that is specific to a particular vegetation type or industry; examples include moorland management, forestry or farming.

Photos B8.6 and B8.7 Showing a control line being cut into heather and subsequently how successful this was in containing fire spreadPhotos B8.6 and B8.7 Showing a control line being cut into heather and subsequently how successful this was in containing fire spread

Photos B8.6 and B8.7 Showing a control line being cut into heather and subsequently how successful this was in containing fire spread

Advantages

8B8.56 The use of machinery to construct control lines can bring a number of important advantages over manual construction which include:

  • Control lines are constructed much more quickly.
  • As they take less time, they can be built closer to the fires edge thus reducing the size of the fire footprint.
  • Depending on the type of machine, a greater channel of fuel can be removed creating control lines of a greater width.
  • Machines can be used to dig control lines to a greater depth.
  • Fewer personnel are involved in the operation.
  • Control lines can be constructed through denser and courser fuels.
  • Less physical effort is required.
  • Equipment can often be provided by land agencies who also have skilled operators.
  • Equipment is often specifically designed to remove fuel of a particular type.

Disadvantages

8B8.57 There are a number of disadvantages which personnel need to be mindful of when using mechanically constructing a control line. These include:

  • Variations in the types of vegetation or soil types encountered across the landscape may require the use of different machines.
  • Difficulty in operating over all types of terrain, steep slopes or soft ground may restrict the use of machines.
  • Access or egress, to and from, the scene of operations may be restrictive.
  • The machine may break down placing the operator at risk or resulting in the loss of the machine.

8B8.58 Machines can either be used independently or work with the support of a hand crew. While a machine is at work, it must be continually supervised and arrangements must be made for the operator to be included within the LACES protocol. Machine operators must not work in isolation; no one should be allowed to work alone when at a wildfire.

Photo B8.8 Forestry Commission equipment clearing woodland

Photo B8.8 Forestry Commission equipment clearing woodland

Photo B8.9 Heavy machinery being used to clear scrubland

Photo B8.9 Heavy machinery being used to clear scrubland

Parallel Attack

8B8.59 Parallel attack is a tactic that may involve a number of different techniques. It is effective against fires of various levels of intensity, but is normally employed as an indirect attack method against fires of higher intensities.

8B8.60 The main objective of parallel attack is to secure the area around a fire through the construction of control lines. The construction of these should begin from a strong anchor point to the rear of the fire and move around the flanks. These should be built far enough from the fire to ensure that they are completed in good time. If the control lines are considered to be too weak to secure the area, then the vegetation between the control lines and the fire can be burnt out. Burn out operations can also take place as the lines are being constructed.

Fig. B8.6 A Parallel Attack with control lines and burn out operations occuring simulataneously

Fig. B8.6 A Parallel Attack with control lines and burn out operations occuring simulataneously

Fig B8.6 shows two ploughs constructing a control line around each flank of the fire. The vegetation between the lines and the fire are being burnt out depriving the fire of fuel and preventing the wildfire from burning up to the control line.

Mop-up

8B8.61 Mop-up is the action involved in ensuring that a fire does not reignite or escape once it has been brought under control. The burnt area has to be secured by extinguishing any hot spots or burning material. Mop-up operations should be started as soon as suppression methods are applied and should continue throughout the incident. As an attack is launched efforts should be made to dampen down or dig out any hot spots as progression is made along the fire's edge.

8B8.62 Once a fire has been contained it is important to extinguish any burning material, especially near to the outer edge of the fire perimeter where burning material may be lying within unburnt fuel. Once the outer perimeter has been secured crews should work inwards exposing and extinguishing hot spots or burning fuel as they go.

8B8.63 To secure the area, existing control lines may be strengthened or new ones constructed. Pockets of remaining fuel can also be burnt out using controlled burns.

8B8.64 Mop-up operations may take a considerable length of time and, depending on the size of the incident and the vegetation involved, continue for a number of days. To maintain efficiencies it is important that FRSs make arrangements to obtain assistance from rural agencies or partners during this closing phase of the operation. At the conclusion of the emergency and mop-up phase of the incident it is recommended that a formal handover of the incident back to the appropriate land owner or land management agency is conducted. FRSs should consider the utilisation of handover agreement forms for this task.

Photo B8.10 A Ranger assisting with damping down hot spots at a fire in the Peak District

Photo B8.10 A Ranger assisting with damping down hot spots at a fire in the Peak District

Photo B8.11 Partner agency workers assisting with mopping-up at a wildfire incident

Photo B8.11 Partner agency workers assisting with mopping-up at a wildfire incident

The Use of Fire

8B8.65 Although the use of fire can be perceived to be a higher risk strategy, in reality if its application is carried out by well trained personnel and the operation is managed correctly, it can be used with confidence.

8B8.66 Only those personnel who have obtained appropriate training and have the relevant experience should be allowed to apply this suppression method operationally. A skilled specialist can apply fire safely to achieve a number of objectives including:

  • The widening of existing control lines
  • Creating control lines
  • Burning out fuel
  • Changing fire behaviour

This section provides a simple overview of the methods involved, and the information given is not sufficient to allow FRSs to apply any of the techniques described.

Controlling the Use of Fire

8B8.67 Without effective control mechanisms, fire may be used inappropriately and the indiscriminate use of fire can lead to dangerous escalations of the situation. It is therefore essential that FRSs that choose to use these methods, do so following a thorough risk assessment and are satisfied that they have robust procedures in place governing the proactive use of fire as a suppression tool. Operationally this should include the Incident Commander's authorisation to use fire on the incident ground.

Fire as a Suppression Method

8B8.68 This guidance encourages FRSs to develop the skills necessary to apply these techniques operationally. Fire provides a means to combat the spread of fire when other tactics are likely to be ineffective or dangerous. If used properly it is a safe, effective and a very efficient suppression method.

Terminology

8B8.69 Internationally, very similar terms are used to describe parts of a wildfire and the fires that are deliberately ignited to suppress it. Examples include back fire, backing fire, back firing, flank fire, flank firing, head fire, ring fire etc. To avoid confusion, in this guidance the term 'fire' refers to terminology related to flaming parts of the wildfire, the term 'burn' describes a fire that has been lit as part of an operational plan.

The Tactical Use of Fire

Defensive Burning

8B8.70 This type of burn involves the removal of fuel by a fire that is extinguished before the arrival of the wildfire. It is normally applied some distance from the fire front and therefore can be planned in good time.

This tactic can be used for a number of purposes including:

  • To remove fuel from along a control line so that the wildfire cannot burn up to its edge.
  • As a method to create control lines in finer fuels. This is a highly skilled and technical procedure that must only be carried out by specialist officers. A line of fire is lit with the head of the fire being extinguished immediately and before it has time to fully develop. The tail fire is then allowed to burn back into the fuel. When the fire has created a break of sufficient width, it is then fully extinguished.
  • To burn out fuel in a controlled way thus reducing fire intensity or altering the fire behaviour.
  • To burn out fuel from areas that have been identified as critical to fire development.

Photo B8.12 A burn out operation in progress to remove surface fuels from a wooded area

Photo B8.12 A burn out operation in progress to remove surface fuels from a wooded area

Offensive Burning

8B8.71 An offensive burn occurs when a fire is lit and allowed to burn into an approaching fire front. This type of burn should be carried out by specialists who have advanced knowledge and experience of applying fire as a suppression method.

The offensive use of fire can be used for a number of purposes including:

  • To reduce fire intensity or behaviour, i.e. when a wildfire is approaching a control line and is generating spot fires. An offensive burn can be used to straighten the flame angle and/or the fire plume. This may reduce the amount of spotting caused by the fire.
  • An offensive burn can be carried out to defend a control line. By lighting a fire along its inner edge, the fire will burn towards the main fire. As the burn moves away from the control line it burns out fuel, broadening its width. Eventually the two fires are drawn together and burn out some distance away from the control line further reducing the possibility of the fire escaping out of the containment area.

Photo B8.13 An offensive burn being carried out to strengthen a dirt track which has been utilised as a control line

Photo B8.13 An offensive burn being carried out to strengthen a dirt track which has been utilised as a control line

  • Fire is a useful way to remove fuel that exists between a control line and a fire front. A good example being when parallel attack is being used as a suppression method. As the control lines are constructed along the fires flanks, the remaining vegetation between the control lines and the wildfire, can be burnt out by offensive burning, this prevents the wildfire making a run through the fuel towards the control line.

Photo B8.14 A joint FRS and land management parallel attack being carried out to remove fuel from the flanks of the fire

Photo B8.14 A joint FRS and land management parallel attack being carried out to remove fuel from the flanks of the fire

Managing an Operational Burn

8B8.72 FRSs that wish to use fire as a suppression method must ensure that they adopt appropriate systems of work, and that personnel have the necessary training and expertise required to safely carry out this method of suppression. Burns should not be carried out by individuals but by crews of trained and competent personnel. These must be supervised by a skilled specialist who has the support of specialist burners and a holding crew. Together, these must operate to a pre-determined scheme or programme of activities which ensures the safety of personnel and effectively manages the activities of the team.

An Operational Burn Crew

8B8.73 Operational crews should consist of the following:

A Burn Supervisor
The burn supervisor carries out a specialist role. They have the responsibility to risk assess, plan and manage the operation. They must ensure that the burn is only carried out if it can be achieved safely.

Burners
Operational burn crews would normally include 1-3 burners. These are specialists with the knowledge and skills to be able to burn out the fuel in accordance with the burn supervisor's instructions.

Holding Crew
A burn crew should include a number of personnel that have the responsibility to maintain on going control over the fire. In particular, they must ensure that the fire does not break out into fuel that is outside the intended burn area. The number of personnel and equipment required to carry out this support role is dependent on the complexities of the operation and should be part of the burn supervisor's risk assessment and plan. A holding crew may be required to carry out extensive work before a burn to ensure that the site is secure.

Types of Operational Burns

A Back Burn

8B8.74 This is a low intensity fire that burns against the wind or slope (or both). The fire should normally be lit along the inner edge of a control line which acts as a barrier; as a result the fire is forced to burn back, against the forces which in other circumstances would have driven it in a forward direction. This is an excellent method to use to strengthen a weak control line as it broadens its width, removing fuel from along its edge. This type of burn can be used either defensively or offensively.

Fig. B8.7 In this illustration a burn has been lit along the closed side of a track and allowed to burn towards the approaching wildfire

Fig. B8.7 In this illustration a burn has been lit along the closed side of a track and allowed to burn towards the approaching wildfire

A Counter Burn

8B8.75 In this guidance the term counter burn is used to describe a fire that is lit with the intention of allowing it to burn into the fire front. Counter burning is an offensive technique that requires an advanced understanding of fire behaviour as it often takes advantage of the in-drafts created by the wildfire. These allow the counter burn to build up momentum and intensity as it approaches the advancing fire front. Counter burns can also take advantage of alignments that allow the fire to be driven towards the wildfire.

Fig. B8.8 Example of a burn using the in-drafts to draw the two fires together

Fig. B8.8 Example of a burn using the in-drafts to draw the two fires together

A Flank Burn

8B8.76 A flank burn is a fire that is lit parallel to the flanks of a wildfire, normally along control lines. This type of operation is often carried out as part of a parallel attack. This type of fire can develop behaviour of high intensity as parts of the burn may find alignments similar to the main fire.

Fig. B8.9 A flank burn being carried out from a strong control line. The helicopter is strengthening the control line by placing a wet line along the outer edge of the control line.

Fig. B8.9 A flank burn being carried out from a strong control line. The helicopter is strengthening the control line by placing a wet line along the outer edge of the control line.

Centre Burning

8B8.77 Centre burning is a complex defensive method used to burn out parcels of vegetation that are enclosed within surrounding control lines.

8B8.78 This technique should only be undertaken by burners with advanced knowledge and experience. The use of centre burns can prevent a burn from developing a strong head fire that may escape out of a containment area. The process involves lighting a fire(s) near to the centre of a plot, followed by secondary ignition(s) along the inner edge of the control lines around the sites perimeter.

The inner and outer fires then interact, drawing each towards the other; as the fire is forced to burn inwards the major fire intensities take place towards the centre of the plot away from the control lines.

Centre burning involves two distinct phases:

Phase One

8B8.79 A fire or a number of fires are lit near to the centre of the area to be burnt, these are allowed to build up some strength.

Phase Two

8B8.80 When the inner fire has developed sufficiently, the closed edge of the control line is lit, this results in the inner fire being surrounded by an outer fire. The two fires then interact causing both to be drawn together.

8B8.81 As this type of burn relies on the interaction between the inner and outer fires, the important issue is the timing of the ignitions. The inner fire must be allowed to develop so that it is of sufficient strength to draw the outer fire inwards.

8B8.82 The outer fire must be lit in good time and must include lighting a fire around the whole perimeter. This usually requires the employment of a number of burners who each take responsibility to ignite a section.

Fig. B8.10 Showing the in-drafts of both fires interacting and drawing the fire away from the control lines

Fig. B8.10 Showing the in-drafts of both fires interacting and drawing the fire away from the control lines

Photo B8.15 A plot being burnt out using the centre burn technique

Photo B8.15 A plot being burnt out using the centre burn technique

Ignition Patterns

8B8.83 There are a number of different ignition patterns that can be used to carry out an operational burn. These pattern techniques can be used to create fires of different intensities, and varying rates of spread. The technique chosen should be appropriate to the situation and be safe.

8B8.84 By selecting the correct ignition technique, control over a burn can be established and maintained. A burn should be planned to generate only the desired amount of fire intensity; this is normally measured in flame length. Skilled personnel can manipulate this by using different ignition patterns within appropriate fire alignments. The Wildfire Prediction System should be used to determine the fire alignment necessary to generate differing amounts of fire intensity within the same fuel types and load. When carrying out a low intensity burn; fuel alignment should obviously be kept to a minimum.

8B8.85 Burn out operations are normally only carried out against strong control lines or other barriers to fire spread. It may be appropriate to alter the ignition pattern to meet changing circumstances such as weather conditions, fuel types or fuel arrangements.

The Three Ignition Patterns

8B8.86 The three ignitions that should be used are:

Lines of fire

Points of fire

Fingers of fire

8B8.87 Each of these will create ignitions of different intensities, but it is important to understand that the alignment of any ignition is of paramount importance. A fire that has the support of wind or slope will result in a burn being more intense than one that is burning against them. It is therefore crucial that the Wildfire Prediction System is used to identify the locations where ignitions can be placed to create burns of the desired intensities.

Lines of Fire

8B8.88 This technique can be used to achieve a number of objectives. It involves lighting a strip or a number of strips of fire through the fuel that is to be burnt. It can be used to strengthen control lines or burn out areas of fuel either as a defensive or offensive tactic.

8B8.89 When using this method to strengthen a control line, the lines of fire should run parallel to the fire break and burn towards it. The first line lit is called the base line and it is intended to remove the fuel along the very edge of the control line and to form a 'base' for subsequent lines to burn into.

Fig. B8.11 Three lines of fire burning out fuel along a control line

Fig. B8.11 Three lines of fire burning out fuel along a control line

8B8.90 Fire intensity can be influenced by altering the distance a fire is allowed to burn through the fuel. A wider spacing between lines will allow a fire to build up momentum and intensity; narrower spacing prevents the fire from reaching its full potential. Depending upon the strength of the control line and the fuel involved, the spacing between lines can be varied to achieve manageable and appropriate fire intensities.

8B8.91 By increasing the number of burners, multiple lines can be ignited simultaneously. Whilst the ignition pattern is ultimately under the control of the burn supervisor, the burners must adopt the appropriate burn techniques and co-ordinate their actions. By doing so they are able to burn out a broader area of fuel much more quickly.

8B8.92 The baseline is burnt very close to and along the control line creating a narrow strip which removes the fuel along its edge. Further lines can then be lit further into the fuel and as the burnt out area increases in width and the control line is strengthened, burns can be placed further and further into the fuel. B8.11 shows three burners working together quickly reinforcing a control line. Lines must be started (opened) and finished (closed) at a strong anchor point. Open lines of fire can result in a fire building up its intensity and possibly penetrating the control line.

Points of Fire

8B8.93 The success of this technique depends on there being little alignment with wind or slope. It is a method that can be used to create an operational burn of lower intensity than those started using the line technique.

8B8.94 Instead of lighting a line of fire, individual points of fire are ignited within the fuel. The intensity of the burn is controlled by the spacing between the ignition points. A lower intensity is created by lighting a greater number of separate fires which burn into each other. Each burn out small areas of vegetation, before reaching areas already burnt out by neighbouring fires. The separate fires are therefore starved of fuel, preventing them from reaching their full potential.

Fig. B8.12 A burn using points that will produce a fire of lower intensity

Fig. B8.12 A burn using points that will produce a fire of lower intensity

Fingers of Fire

8B8.95 This is a method used to create an operational burn of low intensity. It must be lit along a strong anchor point or control line. This technique involves lighting short strips of fire, lit from the edge of the control line into the wind. As the fire is anchored, it cannot burn forwards as a head fire, instead it is forced to burn outwards as a flank fire. The intensity of a fire lit using this ignition pattern is reduced because it cannot be supported by the wind, therefore its alignment is limited to factor one or factor two.

Fig. B8.13 Fingers of fire that cannot develop a head as the control line acts as a barrier, the fires are only able to develop along their flanks

Fig. B8.13 Fingers of fire that cannot develop a head as the control line acts as a barrier, the fires are only able to develop along their flanks

Safe Use of Fire

8B8.96 When using fire as a suppression method it is important to consider the following points:

  • The burn should be part of the incident plan and the burn supervisor must fully understand the objectives of the operation.
  • Permissions must be obtained before the operation has begun.
  • The burn should be carried out by qualified specialist burners who are supported by appropriate and sufficient resource.
  • These resources should include a water capability suitable to the task.
  • A risk assessment must be carried out by the burn supervisor to establish whether it is safe to carry out the burn.
  • The burn supervisor must formulate a safe burn plan which meets the requirements of the local conditions.
  • WPS should be used to help identify how to achieve a fire of the desired intensity.
  • A test burn should always be carried out to confirm fire behaviour.
  • An ignition pattern which creates manageable fire intensities must be used.
  • An operational burn must be started against a strong anchor point.
  • Burners must be cautious and should continually assess fire behaviour, where necessary adjusting the ignition pattern to meet the requirements of the plan.
  • The fire must be restricted to within its intended boundaries; too much fire can overstretch the holding crew, therefore fire activity should be monitored closely to keep it at a manageable level.
  • Whenever fire is being used as a suppression tool, a tactical lookout should observe the operation.
  • If the situation becomes dangerous the operation must be terminated.
  • The holding team should be used to control fire intensities and spread.

The Application of Appropriate Wildfire Tactics

8B8.97 Appropriate tactics are those that, when applied, are safe, effective and efficient. In the UK the predominant tactic will remain direct attack, but it is important that FRSs are able to employ alternative methods.

8B8.98 There are two main fire factors fire officers must consider before deciding on what attack method to use. The first is the potential rate at which the fire will move across the landscape and the second is the fire intensities that will be generated. Obviously it would be inappropriate to use direct attack against a fast-moving intense fire, therefore it is important to obtain an understanding of not only present fire behaviour but also its potential behaviour. Flame length is useful as it is a visual indicator and one that can be measured. Importantly, more experienced officers will be able to predict what flame lengths will be throughout the duration of the incident.

Direct Attack Suppression Methods

8B8.99 Crews using direct attack methods must be of sufficient size, be properly equipped and have the appropriate skills and understanding necessary to apply this tactic successfully. Direct attack is a suppression method that should be used against low to moderate intensity fires having a flame length of about 1.5 metres. Above this height this suppression method becomes increasingly less effective and progressively more dangerous for the firefighting personnel.

8B8.100 Whenever possible, crews working at the fire front should be supported by resources that have the capacity to apply water onto the fire.

8B8.101 If water supplies are limited, instead of being used to extinguish the fire, it should be applied sparingly and used only to lower its intensity. Small amounts of water can significantly reduce flame length resulting in increased effectiveness. The most efficient method of applying water onto a fire is via pressurised systems such as FRS pumps or wildfire firefighting systems such as fogging units. Where these are not available, hand teams should include personnel that are equipped with knapsack sprayers, these can also be used to great effect.

8B8.102 The chart below is not intended to be restrictive but outlines which tactics are more effective when fighting fires of different flame lengths. Indirect attack methods can be used to fight low intensity fires as well as those of higher intensity.

Tactic

Flame length

Primary methods of extinction

Direct Attack

Low intensity fires

0-0.5m

Use of hand tools

Application of water using knapsack sprayers

Application of water using pressurised water systems

Direct Attack

Moderate intensity fires

0.5-1.5m

Use of hand tools supported by knapsack sprayers to lower fire intensity

Application of water using pressurised water systems

8B8.103 Where sufficient water can be applied and a risk assessment has identified that it is safe to do so, it is possible to use water attack to control fires demonstrating longer flame lengths and higher intensities but this becomes progressively more difficult as the flame length increases.

8B8.104 Where a fire has flame lengths that occasionally go beyond 1.5 metres, direct attack methods do not have to be abandoned. Personnel using this method can apply it to areas of the fire demonstrating shorter flame lengths and wait for the more extreme parts of the fire to reduce in intensity. An example of this would be when a fire makes a run up a steep slope; direct attack may still be successfully applied to the flanks and tail, but not to the head. When the head fire reaches the top of the slope, fire intensity and flame length may reduce to a level where direct attack can be re-applied. So long as the loss of control over parts of a fire is not prolonged or sustained, direct attack can be used with success to extinguish the whole fire. When adopting this approach it is of the utmost importance that direct attack is only applied to parts of the fire that is within the threshold of control and it is safe to do so.

Indirect Attack Suppression Methods

8B8.105 Indirect attack methods can be used against fires of all fire intensities; they do not need to be only applied against fires of higher intensities and flame lengths above 1.5m.

8B8.106 For example, in some situations, it may be more appropriate to construct a control line using mechanical equipment, rather than commit large numbers of personnel with beaters and knapsack sprayers along a fast moving fire front.

Tactic

Flame length

Primary method

Indirect Attack

High intensity fires

1.5-3.5m

Use of control lines

Parallel attack

Application of water additives

along control lines

Defensive and offensive use of fire

Aerial operations

Indirect Attack

Extreme intensity fires

> 3.5m

Use of control lines

Defensive and offensive use of fire

Aerial operations

8B8.107 The main tactical advantage gained through the use of indirect attack methods is that they can be applied with success at fires that have gone beyond the control of direct attack methods. As intensity increases direct attack methods become less effective to a point where they can become inappropriate or dangerous. Indirect attack can be used against fires of higher intensity ensuring that personnel are not placed in areas of high risk. The particular techniques used will depend on the circumstances and the skills and equipment available.

8B8.108 As fires become more intense, there is often an increasing benefit in using fire as a suppression tool, this can be used to strengthen control lines, alter fire behaviour or attack the fire aggressively through the use of offensive burns.

8B8.109 A FRS that has a full understanding of wildfire is able to apply tactics that are appropriate to the fire intensity. This may involve using a number of different techniques at the same fire in response to changing circumstances.

8B8 Key Considerations

  • Base all suppression tactics on expected fire behaviour rather than current activity.
  • Consideration should be given to the level of training, expertise and experience of personnel when allocating tasks.
  • If operational burns are to be used then all relevant personnel should be informed.
  • Firefighting operations should always begin from a strong anchor point.
  • Unless a fire is of low intensity, the head part of a fire should normally only be attacked once the flanks have been extinguished.
  • Do not ignore the opportunity to extinguish low intensity parts of the fire such as the tail, before they spread into locations that provide more support to fire development.
  • When fire intensity is high, indirect attack methods should be used.
  • Direct attack (other than aerial suppression) should only be used on the parts of the fire demonstrating lower intensities.
  • Where water supplies are scarce the application of small amounts of water will significantly reduce fire intensity making it easier for hand teams to extinguish the fire.
  • Whenever possible, water or some other form of extinguishing media should be made available when undertaking a direct attack.
  • Indirect attack methods can be used against low or high intensity fires.
  • All burn out operations must be planned and managed by a burn supervisor.
  • Plans should be based on timed intervention when the fire is within the threshold of control of the available resources.