Firefighting foams

- what's safe and what's not?

Published:  01 April, 2006

Let’s start with something all firefighters can appreciate: firefighting foam is either low expansion, medium expansion or high expansion, classified according to the ratio of air to liquid in the foam.

The huge quantities of fluorosurfactant foam used for both fire extinction, cooling and vapour suppression resulted in millions of litres of firewater run-off contaminated with hydrocarbons as well as fluorosurfactant and its fluorine­containing degradation products, needing treatment.
These degradation products are extremely stable in the aquatic environment with lifetimes of the order of decades or more: some are also poten­
tially toxic and bio-accumulative. Is it time for fire brigades to reconsider the use of AFFF-type foams
for incidents that do not require their use but could be dealt with more effectively, with better use of human and financial resources, and without the potential for long-lived impact on the environment, using other technologies?
The containment issue:
Incidents like Buncefield, involving large installa­tions in the petrochemical and heavy chemical industries, require the use of large quantities of AFFF-type fluorosurfactant-containing film­forming foams given current operational techniques. Industrial sites should, however, have containment facilities, i.e., be bunded with dykes or berms and isolated, or at least capable of being isolated, with drainage systems able to hold the entire site inventory plus any firewater run-off.
Containment is frequently not as easy at other types of incident, such as road traffic accidents or air crashes, where preventing the dispersion of the foam-contaminated firewater runoff may be very difficult and the use of foam may itself compromise the efficiency of petroleum-spirit interceptors. Even at large petrochemical incidents involving bunded storage-tank farms, dispersion may become a problem if containment facilities are overwhelmed, destroyed by blast, or the seals between concrete slabs or the concrete itself damaged by the released material. The potential environmental impact of foam and the large volumes used may be limited by restricting its use to actual extinction and the blanketing of volatile liquids rather than using it as a cooling agent for tanks and other parts of the installation.
When do you need to use AFFF?
When do municipal fire brigades need to use AFFF fluorosurfactant-containing foam and when is there an alternative and efficient technology available, which incidentally may have consid­erable price advantages?  Generally speaking, municipal fire brigades have neither the operational experience, the training nor the specialist equipment needed to fight very large petrochemical refinery or chemical process plant fires. Nor do they, or should they, hold sufficient stocks of AFFF or AFFF-AR foam concentrate to mount even the initial attack for incidents of this size, as this would involve a very large capital expenditure with a finite product shelf-life together with requirements for storage.
Rather they should rely on the industry, i.e., the occupier of the premises, for specialist firefighting experience, equipment and adequate foam concentrate stocks held off-site - not on-site as a major incident may destroy the foam stocks!
Specialist training for operational cooperation between the local brigade and the industrial concern is essential, and mandated in law at classified hazardous materials sites, with municipal fire brigades ideally suited to providing both on-site and off-site command and control together with liaison with other emergency services such as the police and ambulance service, as well as infra-structural support involving hose­laying vehicles and high-volume pumps.  After the initial attack has been started, further quantities of foam concentrate will have to be obtained directly from major foam manufacturers as part of their emergency support service.
So when does a municipal brigade need to use an aqueous-film forming foam (AFFF) rather than any other method? Should any stocks of AFFF held by the brigade be as the alcohol-resistant variant ‘just in case’, i.e., AFFF-AR? How does an incident commander know whether to use AFFF or AFFF-AR before reaching the site of the fire and before specialist information has become available? Although tempting, the ‘one size fits all’ philosophy should not be followed. The chosen foam must be fit for purpose, and this includes as part of the overall risk assessment consideration of the environmental impact and whether it is justified.
Look for the chemical signature ;
Foams for Class B hydrocarbon fires are tested on pool fires in pans of various sizes, whether to UL 162, EN 1568 or the ICAO standard. This is where the fluorosurfactant aqueous-film forming foam (AFFF) comes into its own by spreading as film across the burning surface.  There are, however, fluorine-free foams including self-healing foams, e.g., Solberg’s Arctic Foam or Bio-Ex’s ECOPOL, which perform to the same standard specifications. Yet how often does a municipal fire brigade have to deal with a contained pool fire? Rarely.  It is more common, for example at a road traffic accident involving a tanker or a pipeline fracture, to have to deal with either a running fuel fire or to provide vapour suppression and cooling. In certain situations either powder, or a combined attack with powder and foam, is more appropriate although rarely used by other than industrial firefighters in the petrochemical industry.  Fires can be thought of as having a chemical signature which tells an incident commander a lot about the fuel. A thick plume of heavy, roiling black smoke with orange flame suggests a relatively high molecular­weight hydrocarbon fire and chemical structures deficient in oxygen, such as diesel, kerosene or heavy fuel oils.
On the other hand, a very hot, almost colourless smoke, indicating lack of soot particles, with bluish or near­invisible flame suggests a fuel that is structurally very high in oxygen, such as methanol, dioxan or acetone. A lazy orange flame with almost no visible carbon particles, burning back to source without explosion, would suggest vaporised LNG (methane). In the first instance, an AFFF would be required as hydrocarbons are non-polar.  In the second case, however, an AFFF-AR or other alcohol-resistant foam would be required to prevent breakdown of the foam by polar fuel molecules. In the third case other techniques are required. It should also be remembered that a forced draft of atmospheric oxygen, or worse a leaking oxygen or compressed-air pipeline, will have the same effect on the smoke from a hydrocarbon fire as substitution with a polar fuel. Flame colour will change from deep orange or red to almost colourless with a bluish tinge indicating combustion to carbon monoxide (CO) and carbon­dioxide(CO2) and smoke, if present, will become whiter. Carbon monoxide levels may be very high and the smoke invisible in the vicinity of a well venti­lated fire,especially in confined spaces, whereas you can almost always see smoke that is high in soot or other pyrolysis products. Breathing apparatus should always be used as well CO detection equipment, especially for personnel in the vicinity who are not wearing respiratoryprotection, for example, incident control staff or other Emergency Services’ personnel.
Horses for courses:
Techniques that are suitable for petroleum product firefighting, including liquified petroleum gas (LPG) or fuel-oil/gasoline spills, may not be at all suitable for liquified natural gas (LNG). The physical properties of the fuel are extremely important. For example, LPG forms explosive mixtures with air, being stored as a liquid under pressure at ambient temperatures, whereas LNG (-260°F) kept at atmospheric pressure in insulated
Richardson (Protection Technical Manager, SembCorp), Martin storage tanks. Hough (Sales Manager, Specialist firefighting techniques are required Angus Fire).
for LNG including the use of high-expansion foam for vapour suppression and powder, which interferes with free radical propagation, for flame extinguishment. The TEEX facility at the University of Texas A&M’s Brayton Field offers the world-renowned expertise and equipment necessary for firefighter training for operations involving LNG both at industrial installations as well as during transport by road or water, as might be encountered by municipal fire brigades.  So does AFFF have a place in municipal fire brigade operations? Yes, but it is limited to dealing with contained hydrocarbon fires where the foam’s film-forming properties are essential. Other methods are available for most other situa­tions and are likely to have a much reduced long­term environmental impact.
Alternative technologies provide ways of reducing the environmental impact of firefighting operations. Use of 1% or 3% finished foam rather than 6%, AFFF with a reduced fluorine-content or even fluorine-free foams such as those available from Solberg Scandinavian or Bio-Ex, all can contribute to reducing the environmental legacy of extinguishing fire. Compressed air foam systems (CAFS), water mist and fog apparatus, or the use  of combined foam and powder delivery systems, provide alternative extinction technologies for municipal fire brigades.  Modern electronic digital foam proportioning pumps, for example, the Godiva FoamMaster(r) E Series 5.0 or Hale’s FoamLogix(r) Model 5.0, offer adjustable and reproducible induction rates of 0.1% to 10% with either Class A or most Class B concentrates.  Digital proportioning offers repro­ducibility and flexibility difficult to achieve with mechanical eductors, whether in the form of fixed percentage or adjustable units. Various forms of air-aspirating equipment designed to deliver low, medium or high expansion foam, are used under specific condi­tions.  With any proportioning equipment it is essential that the foam concentrate being used should have been approved by the manufacturer of the equipment. Other approvals may also be required before the foam concentrate can be used opera­tionally, for example, from the US Forestry Service when used on wildland fires. Firefighting foam generated with portable or vehicle-mounted induction equipment or from fixed-pipe installations and monitors, has provided effective fire suppression and extinction throughout industry for some considerable time. For applications in the petrochemical, heavy chemical process, liquified gas and aeronautical industries, specialised systems incorporating air­aspirating or self inducting branches and monitors, or high expansion blower-type foam generators, are essential.
Standard methods give rise to a number of problems: the foam may not adhere well to vertical surfaces; it may become contaminated by soot and other debris from the air used to produce it on the incident ground, blocking the mesh that generates the finished foam; normal foam-concen­trate induction rates (3%-6%) result in high costs and high potential impact on the environment; moreover, momentum is reduced on reaching the nozzle, limiting ‘throw’ and penetration of the fire plume by foam to reach the seat of the fire.
Compressed air foam systems (CAFS) inject air under very high pressure into a premixed foam solution stream. The high-pressure compressor is the key to a successful CAFS unit. CAFS produce a uniform stable foam made-up of small bubbles with high momentum and adjustable composition and consistency.
Vehicle-mounted CAFS equipment has found extensive use in combatting structural and wildland Class A fires. The CAF is released using smooth-bore branches as a high-velocity ‘column’ or ‘rope’ of foam making it possible to fight a fire effectively from greater distances. CAFS also use much less water and foam-concentrate than conventional foam induction systems. This is
Angus Fire has announced it has won a major contract to supply SembCorp Utilities UK with Tridol ATF 1x3 fire fighting foam. Based on Teesside in the North of England, SembCorp provides emergency response services to one of the highest concentra­tions of chemical plants and refineries in Europe. With access to the largest industrial foam stocks in the UK, it responds quickly and effectively to fires involving a range of different flammable liquids. “This new partnership gives SembCorp access not only to the latest foam technology, but also to strong technical support. The logistics expertise of the Angus emergency service, which proved so effective at Buncefield, will also help us to source additional foam stocks when we need them urgently,” comments Greg Richardson, SembCorp’s Protection Technical Manager. Previously, SembCorp used a foam product from a different manufacturer. It had considerable post-fire clean-up costs due to an environmentally harmful ingredient called PFOS and has since been withdrawn from the market. Angus Fire’s Tridol ATF is a new generation PFOS­free foam that provides high fire fighting performance and is a 1x3 grade, which is more efficient to handle at incidents than 3x6 grade foams. “SembCorp is leading the way for emergency response organisations that still stock PFOS-based foam. By acting in advance of possible changes in environmental legislation that may prohibit its use at emergencies they are positioning themselves well for the future,” said Martin Hough, Sales Manager for Angus Fire. The new foam will be supplied by J&RA Hawkes & Sons, Angus Fire’s authorised distributor in the North of England. Hawkes is also collecting the old stock and arranging for it to be disposed of by the required method of high temperature incineration, and arranging for the new foam stocks to be tested regularly to ensure that they remain uncontaminated and in good working condition.
Angus Fire is the largest foam manufacturer in the world, producing a complete range of environmentally responsible foams at its factory in Bentham, North Yorkshire. It also manufactures fire hose and fire equipment at Bentham, and provides product sales and customer support from Thame, near Oxford, UK. Angus Fire is part of UTC Fire & Security, which provides fire safety and security solutions to more than one million customers throughout the world. UTC Fire & Security, headquartered in Connecticut, USA, is a business unit of United Technologies Corp., which provides high technology products and services to the building and aerospace industries worldwide. This is highly significant in fighting wildland fires where water may be a scarce resource, having to be transported on-site by tanker.
CAFS also result in less firewater run-off and associated damage in fighting structural building fires where wood is used as the building material of choice, such as in the USA or Australia. As a result of pioneering work by Kim and Crampton of the National Research Council of Canada, it has been shown that properly mixed CAF is able to achieve Class B performance using Class A foam concentrates on hydrocarbon fuel fires. Fixed CAF installations have also been shown to be highly effective.
Apart from CAF units mounted on standard fire appliances, units are available for mounting on the smaller trucks used for wildland or brush fires. Some foam agents can cause contamination of the environment. Preventing foam runoff from entering water courses is a difficult dimension of fire response.  firefighting, or even in vans with a crew of two for rapid response units in an urban setting. The Hale MiniCAFSPro(r) is an independent compressed air foam module with variable foam mix rates between 0.25% and 1.0% for Class A fires, capable of generating wet, medium or dry foam, and of being operated from any vehicle or portable fire pump, including mini-tankers and wildland fire appliances, according to the manufacturer.  The Hale CAFS Attack(r) is a new stored compressed-air foam system designed for use in both wildland and municipal firefighting applica­tions, with two 12,400 litre (440 cu.ft.) storage cylinders and dual CAF discharges providing variable foam consistencies, a wet foam for the initial attack and a dry, shaving-cream like foam for exposed structure protection.
Making decisions:
So what decisions are needed by municipal fire brigades looking to update or modernise their foam capabilities? First, the foam must be fit for purpose. As pointed out in previous issues of both Fire & Rescue and the Industrial Fire Journal, there is no satisfactory one-stop solution.  Film-forming Class B foams do not perform as well as specially formulated Class A foams in dealing with Class A carbonaceous and structural fires as they do not penetrate properly. Training needs have to be considered.  In most European countries the heightened sensitivity towards environmental contamination means that any potential environmental impact of using foam for training purposes must be mitigated either by using a so-called eco-neutral ‘training’ foam, or by conducting training at a site with good containment and post-incident treatment facilities whenever a ‘real’ foam must be used for training and testing purposes, i.e., at airport or harbour facilities.  Ease of use, raw material costs, storage stability and any special equipment needs have to be taken into account. Unless you know you have a high polar solvent risk, why buy the more expensive AR grades?
Finally, municipal brigades need to re-evaluate the full range of modern extinguishing technologies in order to identify those that are most ‘fit for purpose’, meaning most efficient at extinguishing and controlling fire whilst at the same time minimising their environmental footprint. Brigades shouldresist the temptation of choosing a solution aimed solely at achieving operational ‘convenience’ oratensuringthatoperationalpracticesremainedunchanged, at the cost of fitness for purpose!

  • Operation Florian

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