I’m sitting watching television and a segment came on about the potential hazards of fire fighting foam. It seems like a good opportunity to research and find out a little more information on hazards to firefighters and the community. The publicity has certainly been quite negative in Australia over recent years.
It seems like research, by a number of institutions, has found that there are concerns and potential problems with the use of fire fighting foam containing Perfluorooctanesulfonic (PFOS) acid. PFOS has been associated with chronic kidney disease and has been detected at relatively high levels in wildlife in areas where these foams have been used. Associated levels are considered high enough to adversely affect well-established health parameters. Thus the continued use of fire fighting foam containing PFOS would be problematic. Potentially provide a number of negative health outcomes in both humans and wildlife.
What is fire fighting foam made of?
Used generally for the suppression of fires it’s very versatile and can be seen in use during forest fires and at petrochemical fires. Primarily it is sufficient that lowers the surface tension between two liquids, a gas and a liquid or a liquid and a solid. Organic solvents are used and provide a formula with properties that enhance fire fighting capabilities across Australia and the world.
Some of these organic solvents include, but aren’t limited to, trimethyl-trimethylene glycol and hexylene glycol. To ensure foam is effective and does not expand rapidly thus becoming affected by strong winds or down draughts. Manufactures use stabilisers and corrosion inhibitors such as Lauryl alcohol.
The expansion rate of fire fighting foam.
Firstly, low expansion foams are probably the most common types of fire fighting foam. They can be rapidly deployed and with a relatively low-viscosity have an expansion ratio of less than 20 times. One feature of such foams is that they tend to cover large areas in a quick time frame.
Secondly, medium and high expansion foam have an expansion ratio of 20 to 100 and 200 to 1000 respectively. Thus, there is a foam solution for most applications. Whether fighting house or forest fire.
Classes of fire and foam
Fire fighting foam may have a number of applications but generally, they are used for Class A (normal combustibles like paper and organic materials), And Class B fires associated with the flammable liquid. There are other types of specialist foams which may be used in other classes, but they are very rare.
As I mentioned earlier the design and makeup of fire fighting foams contributes to the lowering of surface tension. For example, Class A foam is used on forest fires because it generally penetrates into the fuel, raising the moisture content. This encouraging increased extinguishing capability as compared to plain water.
As a side note – firefighting boots made of leather will absorb water much quicker if it is treated with Class A fire fighting foam. Sometimes making them very hard to polish even after they have dried out.
History of fire fighting foam
Water has been used to extinguishing fires for millennia. In 1902 a Russian chemist, called Aleksandr Loran, produced a fire fighting foam whose properties are very similar to those used today. At the time cooking oils started many devastating fires. Aleksandr developed the foam fire extinguisher and patent it in 1904.
His initial tests used to powders mixed with water via a foam generator. The powders were sodium bicarbonate and aluminium sulphate. To stop the foam from creating large bubbles a small amount of saponin or liquorice was added, which in turn provided some stabilization.
Development of fire fighting foam slowed for many decades until the 1970’s when Alcohol Resistant – Aqueous film forming foam was produced. A Class B foam generally used for flammable liquids has had many chemicals added over the past fifty years. With some having adverse effects on life and the environment.
Since the 1970’s organisations, both private and government, have been using Class B foam for suppressing fires involving flammable liquids. To prepare for an emergency response there has been a need to use equipment and solutions during training.
As such where additives have been included in the fire fighting foams. There has reportedly been a number of firefighters suffer from associated health effects. An investigation into the long and short term effects are ongoing in many countries across the world.
Forest fire fighting foams
Probably one of the largest users of fire fighting foam is the forest firefighting industry. Its ability to be applied across a large area and slow breakdown time make Class A foams useful. As with Class B foams, there is ongoing research into their effectiveness.
This again may be problematic as chemicals are added and removed. With fire fighting foams being applied too often pristine forest areas. It is essential therefore that manufacturers carry out extensive testing and research so there is little if any impact on firefighters, communities and wildlife. It would be noted that most fire services around the world to try to keep fire fighting foams away from waterways.
I may have only brushed the surface of fire fighting foam. I think we have probably established that there is a significant role for these type of foams in firefighting.
Their ability to stop the vapour release during flammable liquid fires. And the ability to lower the surface tension of materials during fires involving Class A fires is a real benefit to firefighters. There will always be a place for fire fighting foams when fire occurs and it would be a sad day for firefighting if they were phased out.
Even so there is a real need to ensure that the appropriate testing and research is carried out prior to any use. The investigations into PFOS contamination is ongoing and may result in harm to those who were exposed. This shouldn’t have happened and must not happen again. Fire fighting foams seem to be hazardous and should be treated with caution.