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Class A Foam and CAFS Training

Class A foam concentrate is a synthetic chemical additive that reduces the surface tension of water so it can penetrate combustible fuel surfaces. When mixed with water it creates a foam solution that is more effective than plain water for flame knockdown and fuel cooling when used for a fire attack.

A compressed air foam system (CAFS) consists of a water source, a fire pump, an air compressor and a foam proportioning system. This system aspirates the solution by introducing compressed air, which allows for a more efficient use of the firefighting media. This move from hydraulic to pneumatic pressure enables fire crews to maximise their water supply and ultimately reduce the property damage that can occur when fighting fires with water alone.

Class A foam concentrate supplied through CAFS enables a more efficient use of resources, which has undoubtedly led to an increase in Class A foam use within fire services across the world. More importantly, this has had a positive impact upon firefighter safety. By reducing knockdown times, the use of CAF can dramatically decrease the exposure time for firefighters within risk areas. Using well trained techniques, the resulting reduction in heat and toxic by-products can have only a positive impact upon firefighter safety.


Class A CAFS can be used in wet and dry modes, each offering different benefits. Wet CAF is used for fire attack and cools fuel surfaces. The bubble structure created by the CAFS enables the firefighting media to adhere to three dimensional surfaces. This allows the majority of the finished media to evaporate and cool on the fuel surface.

By removing a quantity of water from the mixture, a shaving foam consistency dry CAF firefighting media can be produced. Dry CAF should not be used for firefighting attack. Its purpose is to create a protective barrier and to provide exposure protection to reduce the impact of an impinging flame against a nearby building or structure.

Within Devon and Somerset Fire and Rescue Service (DSFRS), CAF has been used operationally and has provided a more targeted efficient use of resources at certain incident types. Crew Manager, Matthew Head, a CAFS instructor at the DSFRS Academy said: “Within the Academy we impress upon students the importance of a clear underpinning theoretical understanding of Class A foam and CAFS. This is reinforced with reference to case studies based upon recent incidents and real hands on practical sessions to ensure that all our personnel are operating using safe, effective and quality assured techniques”.


The Training Academy teaches students how to use Class A foam and CAFS, and also focuses clearly on when it should not be deployed, which is why quality training underpinned by clear policies and procedures is the cornerstone of the Academy’s approach to training. Matthew Head explains: “We do not teach the use of CAFS for internal firefighting. There are currently no guidelines for the use of CAF as a gas cooling media in compartment firefighting”.

As already pointed out, a major benefit associated with using CAF is that the water usage is greatly reduced. When water is used at fire related incidents, around 80 percent of this firefighting media is lost in run off, which ultimately can be full of contaminant. This can end up washing into surface water drains and other water supply systems. Another advantage of using CAF is that the hose lines are around 60 percent to 70 percent lighter, which makes a huge difference in terms of manual handling.

Matthew Head continued: “In the 1980s, Class A foam was extensively used for wildfires in the USA. Over the past three decades we have seen its use develop into other incident types. Locally we have seen it used at thatch (roofs built with straw or water reed) fires, fuel spill/pool fires, large refuse disposal sites and wildfires to name a few. With the current international financial climate it is not surprising that the use of Class A foam through CAF systems is becoming an international trend; fire and rescue organisations are having to solve an equation that involves improving firefighter safety within an ever decreasing pool of resources”.

CAF can be pumped over large distances, due to the use of pneumatic pressure rather than hydraulic pressure. Station Manager, Chris Pratt, a CAFS trainer at the Academy added: “It is very important to emphasise the hazards of using pneumatic pressure to the students on courses as firefighter safety is always our top priority”. Ultimately one of the main benefits of CAF to DSFRS is that it is a more efficient use of resources. The jet has a longer reach, approximately 20 percent further, which allows the crews to stand further back when they are defensive firefighting and therefore improving firefighter safety.”

Matthew Head recounted: “When I was on-station I attended an incident at a tyre remoulding factory. At the time of the incident the introduction of CAF was in its infancy within DSFRS; only one watch in the city was trained in its use and many of the flexi-duty officers were unaware of its benefits. In the early stages of the incident a lot of water was used to try to extinguish this large fire, when in actual fact it was achieving nothing, particularly as we had difficulty getting water to the incident.” He continued: “The fire was well developed and was not going out with the water being applied so, after a discussion with the officer in charge, it was decided to try CAF. The wet CAF quickly soaked in and started to cool the pyrolising surfaces, the smoke disappeared and visibility improved”. Once CAF was deployed, around 50 percent of the fire had been extinguished in roughly ten minutes and, at this point, the watch had been there for well over two hours.

At this particular incident the eight pumping appliances had delivered nearly 400,000 litres of water in over two hours of fire attack. The single CAF unit extinguished the fire using 2,200 litres of water and 11 litres of foam concentrate in a fraction of the time. It is important to stress that CAF is not right for every incident; it is another tool for firefighters to use in the correct situation supported by robust policy, procedures and quality training.

From 1st April 2011to 31st March 2012 DSFRS attended 762 vehicle fires (vehicle fires account for only 14 percent of all fires attended in that time period). If crews had used water only at these vehicle fires then approximately 1,143,000 litres of water would have been utilised. With water use, traditionally, there is about an 80 percent run off, which contains diluted toxins that disappear down the drain. In that same time period, if CAF had been used exclusively using DSFRS procedures those same vehicle fires could have been extinguished using just 22,862 litres of water.

With car fires in particular the principle when using CAF is that all of the firefighting media should be contained within the vehicle. Matthew Head explained: “As a fire service we are trying to encourage innovative, safe and efficient techniques that challenge the traditional techniques we have always used. We are learning from our experiences operationally and have been feeding this back into our training”.

Anyone wishing to train in CAF would need to make a strategic decision as an organisation as to whether they would like to go down this route. The importance of having the correct training is that CAF uses pneumatic pressure rather than hydraulic pressure and there is a risk involved in that. If an organisation does make the decision to use CAF there is an initial investment involved including training, the Class A concentrate, the CAFS itself and smaller fire engines if required.


With CAF, smaller volumes of water can be carried on fire engines meaning that the media is being used much more efficiently. Therefore a small appliance has the firefighting capability of many fire engines, which enables more efficient use of resources. The benefits of smaller fire engines include less weight due to the size and the smaller amount of water needed. Better access can also be gained to incidents in places like Hong Kong, for example, where the roads are narrow. Much smaller fire engines would be of great benefit with regards to ease of access to incidents and would cut the response time greatly.

Recently, Wicklow County Council in Ireland pleaded guilty to safety violations and was fined €3 million. Firefighters Mark O’Shaughnessy and Brian Murray died at an incident where CAF was used incorrectly in 2007. Mr O’Shaughnessy and Mr Murray entered the disused ink factory with CAF and had to be rescued when they did not respond over the radio. Two other firefighters attempted to rescue them using a ‘pulsing’ technique with the CAF; however, it failed to work in the way they expected and had no effect. It became apparent during the hearing that they not been given hot fire training using CAF. This incident clearly highlights the importance of receiving the correct training and having robust policies in place.

The Training Academy backs up its CAF training with a vigorous policy, highlighting that the service is not moving away from fire behaviour techniques and that CAF is just another useful firefighting medium to be used in certain instances. It is also evident from the County Wicklow case that CAF training needs to be provided for different types of firefighting incident scenarios. Chris Pratt pointed out: “If our crews decide to take a CAF branch in to a compartment fire they must have a safe system of work that is gas cooling, with water at the right droplet size and at the right pressure”.

The Academy is an Institution of Fire Engineers and Edexcel accredited training centre. The DSFRS Academy has designed a day-long course for Class A foam. It touches upon operation and focuses on the hazards and risks involved as well as the theory behind the application of Class A foam at different incidents. The Academy is in the process of building a thatch training rig, which will look at how CAF can be best used at thatch incidents.

The Academy is currently looking into utilising a car that will be used to simulate vehicle fires. The Training Academy CAFS courses can be tailored to suit individual needs. CAF refresher training is available and the Academy instructors are happy to offer advice if needed. DSFRS has gathered a large amount of evidence-based information, data and case studies, policies and risk assessments through using CAFS operationally and for training for the past 15 years. The Academy can also offer Class A and Class B foam courses.

Jessica King

Jessica King is Training Academy Commercial Support Manager at Devon & Somerset Fire & Rescue Service

 For more information, go to www.dsfire.gov.uk/trainingacademy

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