Fluorine foams remain indispensable to industrial firefighting, expert says
Opponents of firefighting foam containing fluorinated chemicals fail to fairly weigh the overwhelming benefits of these products against evidence that exposure can ultimately lead to adverse health effects in humans, said Mitch Hubert, a leading chemist or “formulator” working in this specialized market.
Speaking to an international audience of industrial fire responders in October, Hubert said that fluorinated foams are under attack from an environmental standpoint on a worldwide basis.
“That has really led us to a crossroads in the firefighting foam industry,” he said. “Do we stay with fluorinated foams or go to non-fluorinated foams? There are advantages and disadvantages on both sides of that argument.”
Chief among the disadvantages for industrial firefighters is the lack of a substantial track record of success using non-fluorinated foam, Hubert said.
“Fluorine free foams have not proven to be as effective in large catastrophic fire,” he said. “This is much of what the (firefighting) world is struggling with right now.”
Hubert, vice president of product development for The Solberg Company, addressed fire responders attending the second annual US Fire Pump Big Water Symposium held at Louisiana State University’s Carrol L. Herring Fire & Emergency Training Institute in Baton Rouge, LA.
Earning degrees in chemistry and biology from Northern Michigan University, Hubert joined Ansul Fire Protection in 1978 to develop new fire suppression and extinguishing agents. After a stint at Dynax Corporation, a supplier of specialty fluorochemicals, Hubert joined Solberg in 2014.
For many years, Hubert has worked first hand with a category of man-made chemicals known as per- and polyfluoroalkyl substances (PFAS), essential in making the fluorinated surfactants used in firefighting foam and hundreds of other consumer products.
“There is a tail that hangs off a hydrocarbon surfactant molecule that can have a number of carbon atoms on it,” Hubert said. “If we replace each of the hydrogens with fluorine, the molecule is now perfluorinated. If the molecule is polyfluorinated that means there could still be some hydrogen atoms on those carbon tails.”
Research shows that two PFAS chemicals – perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) can accumulate and stay in the human body for long periods. In 2016, the Environmental Protection Agency issued a health advisory warning about concentrations of these chemical found in drinking water.
“It set the limits for PFOS and PFOA, and their two acid salts, at 70 parts per trillion as the maximum concentration for drinking water,” Hubert said. “As the EPA puts it the limit is designed to provide Americans, including the most sensitive population, with a margin of protection for a lifetime of exposure.”
Finding PFOS and PFOA in drinking water has prompted a call for greater regulations in many states and communities.
“They are finding it in drinking water primarily any place that there was training or testing of AFFF or other fluorinated foam compounds,” he said. “Just about every airport in the United States has some level of contamination.”
Hubert said he prefers to separate “legacy” issues arising from an era when training and testing was done with full strength firefighting foams from today’s more judicious use of better formulated products.
“At that time, we didn’t know about the bio accumulation and we didn’t know about the toxicity,” Hubert said.
Being able to even measure a concentration as minute as parts per trillion is a fairly recent development in modern chemistry, he said.
“When I first started in chemistry analyzing anything to the level of parts per million was a tough thing to do,” Hubert said. “Then we got to parts per billion. Now we are talking about parts per trillion. We are getting lower and lower.”
The EPA Health Advisories are non-enforceable and non-regulatory, intended to provide technical information only. However, governments in some states or in other parts of the world have moved to place severe restrictions and even outright bans on these chemicals.
“Australia is one of the most severe places as far as getting rid of fluorinated foams,” Hubert said. “You can still use fluorinated foam but you have to be able to collect and treat every bit of it you put on the fire. If not, you are responsible for steep fines and possibly even imprisonment if you are found negligent.”
As a result, most companies operating in Australia have discontinued any use of fluorinated foam. However, in many places no restrictions apply to fluorinated foams at all.
PFAS substances are found in industrial applications and consumer products such as carpeting, apparels, upholstery, food paper wrapping and metal plating. Certain PFAS chemicals are no longer manufactured in the US, such as those covered by the EPA’s PFOA Stewardship Program in which eight major chemical manufacturers agreed to eliminate the use of PFOA and PFOA-related chemicals in their products.
PFOS based surfactants manufactured using the electrochemical fluorination process were used in all 3M Lightwater firefighting foams, discontinued in 2001 based on the company’s concerns about persistence in the environment.
“There are still stocks of it all around the world,” Hubert said. “In the United States it is perfectly legal to use it. In the European Union it is not, nor is it legal in Canada.”
The Fire Fighting Foam Coalition, a not-for-profit organization formed by manufacturers recommends that any remaining 3M AFFF and alcohol resistant AFFF be removed from service immediately, he said.
“The FFFC recommends that AFFF concentrates be disposed of at a hazardous waste facility,” Hubert said. “These include any C8 or longer products that are out there.”
Any foam concentrate older that four-to-six years is likely to have some C8 content, he said.
PFOA based surfactants manufactured using the fluorotelomer process common to all other brands of fluorinated firefighting foams on the market also have legacy issues due to C8 chemistry.
“PFOA for a long time was right on the border line of being bio accumulative,” Hubert said. “Finally it became problematic too.”
Firefighting foams using PFAS have drawn special scrutiny because the products are almost 100 percent “emissive,” Hubert said.
“That means that just about everything we use from this bucket winds up on the ground where it can wind up in groundwater, which has caused a lot of problems,” he said.
Years ago, regulators evaluating a chemical for use in the environment applied the old “three strikes” rule or “PBT,” Hubert said. “P” stood for persistence, “B” for bio accumulative and “T” for toxic.
With regard to persistence, the carbon-fluorine bond is the strongest found in nature, Hubert said. That means PFOS and PFOA in the environment can last almost indefinitely.
“Anything we spill or use from a container of AFFF or film forming fluoroprotein foam, has that perfluorinated tail I talked about and pretty much stays around forever and a day,” Hubert said.
By itself, persistence is not necessarily bad for the environment, he said.
“To determine that we have to dig down further and see if there are other effects that might interest us as consumers of a product,” Hubert said.
Next in the three strikes rule is bio accumulative.
“By bio accumulative we mean that as it moves up the food chain, anything that was ingested lower winds up staying in that organism when it gets eaten by someone higher up the food chain,” Hubert said.
For the most part, chemicals are processed out of the human body by the liver and kidneys. But certain PFAS chemicals can accumulate and stay in the body for long periods. However, even with two strikes – persistence and bio accumulation – the chemical in question did not merit regulatory concern.
Toxicity proved to be the third strike for PFOA and PFOS. Both with perfluorinated tails eight carbon atoms or longer, these suspect PFAS chemicals are thought to trigger adverse health effects in the human body at sufficient concentrations. Studies link PFOA and PFOS to reproductive and developmental, liver and kidney, and immunological effects in laboratory animals.
According to the EPA, the most consistent findings from human epidemiology studies are increased cholesterol levels among exposed populations, with more limited findings related to infant birth weights, effects on the immune system, cancer and thyroid hormone disruption.
“There is a basis for having a concern over PFOS and PFOA, the C8 chemistry and longer chain lengths,” Hubert said.
However, this third strike did not necessarily mean game over for fluorinated firefighting foams, Hubert said. Formulators simply switched to C6 chemistry – a hydrocarbon surfactant molecule with a perfluorinated tail of six carbon atoms.
“While still environmentally persistent, C6 chemistry is not bio accumulative and the toxicity levels were orders of magnitude lower than C8 and longer chain lengths,” Hubert said.
However, the environmental community has now chosen to further extend the entire persistence-bioaccumulation-toxicity argument, he said. Longer chain fluorochemicals tend to adhere to the surfaces of active soils such as clay. Shorter chain fluorochemicals are more mobile and distribute more easily through the world’s water column.
“Now, instead of PBT, the environmentalists want to think in terms of PMT” -- “P” for persistence, “M” for mobile and “T” for toxic, Hubert said.
To counter the further tightening of regulations, fluorinated surfactant manufacturers are making great strides in the purity of precursors used in firefighting foams.
“A C6 fluorochemical today can have purity greater than 99.9 percent,” Hubert said. “Some of that remaining impurity is C4 and a very small amount of it is C8. So we are talking about parts per million levels of impurity in the precursor used to make the fluorosurfactant that goes into the finished firefighting foam concentrates.”
Admittedly, C6 chemistry costs more, needing greater amounts of the chemicals involved to achieve comparable performance. Some manufacturers, trying to stay competitive with the previous C8 chemistry, turned out product that did not perform as well in some cases, he said.
However, Hubert had a one word response to concerns that C6 fluorinated foam chemistry today is not as effective at the previous C8 chemistry – “hooey,” meaning nonsense.
“Typically, a formulator always formulates the product to pass performance tests with some margin of safety,” he said. “Ninety-nine percent of the time I run that fire test I’m going to put the fire out."
By contrast, some approval agencies grant their acceptance if the product can pass the performance test at least once, no matter how many other times it failed, he said.
Offering comparable performance, the new fluorinated foams have one other key advantage. Fluorinated foams utilizing C6 chemistry are not covered by the EPA health advisory on drinking water, he said.
“The question becomes will C6 foams eventually be regulated in the near future because of this growing PFAS awareness,” Hubert said.
Apart from potential health impact, the most important factor to consider about industrial firefighting foam is will it put out the fire. As of yet, fluorine free foams have not proven to be as effective in large catastrophic fire when applied at the same application rate as fluorinated foams, he said.
In a demonstration separate from Hubert’s address, a scaled-down live-fire test compared the effectiveness of fluorine and fluorine free foam. Known as a plunge test, finished foam was applied to a full surface fire in a 42-inch diameter pan at a marginal application rate of 0.06 gallons per square foot.
Proportioned and shot at one percent, the fluorine containing firefighting foam extinguished the pan in 41 seconds. By comparison, fluorine free foam proportioned and shot at three percent took more than three minutes to extinguish an equal size fire.
“If you don’t get collapse on a (full sized) tank fire within the first 15 minutes or so, you’re probably doing something wrong,” Hubert said. “That something, more often than not, is tied to either improper proportioning ratio or too low an application rate.”
As application rate drops lower and lower, the foam is consumed by the flames so fast that it burns away or does not reach the fire, he said.
Fluorine free foams are not without environmental concerns, Hubert said. Principal among these is an increased toxicity in water.
“In some instances you have runoff going into a relatively small body of water,” Hubert said. “You could potentially wind up with a fish kill because of the toxic effects of the surfactants in fluorine free foam as opposed to fluorinated foams.”
If firefighters plan to use large non-aspirated monitors for large volume over-the-top foam application, fluorine free foam can present special problems, Hubert said.
“You need to aspirate fluorine free foams if you’re going to be fighting certain fires, especially high vapor pressure fuels like gasoline,” he said. “You’re more likely to get into trouble if you have a fuel-in-depth fire as compared to a spill fire.”
Delivery to the fire may require the use of aspirated foam tubes with all the disadvantages that come with that, Hubert said.
“You have to put things in the tube that makes the foam solution entrain air so that it delivers foam, not milky water,” he said. “That takes energy, reducing the range produced by your discharge device. It’s going to be a shorter distance than if you were not using an aspirated discharge device.”
Firefighters forced to use an aspirated foam tube will have need of two nozzles, including one that can produce a variable pattern if the heat becomes overwhelming, Hubert said.
“Please don’t put water in that one,” he said. “Instead, use foam solution, even though it’s not making good foam. You don’t want to water down the foam blanket that you’re getting out of the aspirated foam tube.”
Logistics is another key advantage offered by fluorinated foam, Hubert said. Fluorinated foam proportioned at one percent represents a lot less foam concentrate to be handled than fluorine free foam proportioned at three percent.
“Let’s say I’ve calculated in my pre plan that I need 5,000 gallons of foam concentrate to put this fire out,” Hubert said. “That’s not counting what you’re going to need post fire for securement. Now, if I have to proportion at three percent, I’m up to 15,000 gallons of concentrate. If I have to proportion at six percent I’m up to 30,000 gallons.”
Taking into consideration the frequency that lightning strikes ignite storage tanks, these fires are often fought when weather is at its worst, he said.
“You’ve got all this soft and soggy earth everywhere and now you’re trying to move large, heavy quantities of foam stock around the area,” Hubert said.
Compatibility between different brands of fluorinated foam makes it possible to marshal like product from a variety of sources if necessary, he said. This may not be possible with fluorine free foams as compatibility between different brands of products is unlikely at this time.
“With aqueous film forming foam, we get this watery film that works against Mother Nature,” Hubert said. “We fool Mother Nature because of the very super-low surface tension that fluorochemicals bring to the equation.” This low surface tension allows the aqueous film to form over hydrocarbon fuels.
Think of that film as a layer of ball bearings that run out in front of the foam blanket and extinguishes the fire before the foam bubbles reach it, he said. Fluorine free foam lacks the essential quality that makes this possible.
“If I add fluorochemicals to my foam, not only can I make it film forming but I can also make it shed fuel, a property known as oleophobicity” Hubert said. “That’s very important when I’m talking about taking a large mass of foam solution, shooting it out of a large nozzle tip and having it strike the surface of a hydrocarbon fuel 100 feet away with substantial plunging of the foam beneath the fuel surface.”
Take a fluorine foam bubble and place it in a Petri dish containing gasoline. Nothing happens, Hubert said. But place a bubble formed from fluorine free foam in that dish and the bubble acts just like a wick on a kerosene lamp, drawing the flammable liquid into itself.
“With any substantial plunging of the foam below the fuel surface that whole foam blanket is going to burn,” Hubert said.
Fluorine free foams need good foam quality and a long-lasting foam blanket because they lack film formation and oleophobicity, Hubert said. Because they rely on having a slow draining foam, manufacturers add more of the polymers typically found in AR type products.
The way to prevent fluorine free foam from “absorbing” the flammable fuel is to cap the contaminated foam at the foam/fuel interface with a layer of slow draining foam that is not contaminated by the fuel. But the added polymers thicken the foam, creating problems with the proportioning devices being used.
“If you know ahead of time you can make accommodations for that,” Hubert said. “The time to make accommodations is not when you’ve got a fire burning and the guy from down the street shows up with foam twice as viscous as yours.”
Added viscosity of fluorine free foams can also create havoc with smaller, electronic pumps used for proportioning.
“The small ones use piston or plunger pumps,” Hubert said. “High viscosity materials tend not to be very happy with those. Take a hypodermic syringe and pull up a viscous liquid. The plunger tends to separate from the liquid column.”
Rather than fluorinated surfactants, fluorine free foams may use silicone surfactants. Typically, these are not as persistent in the environment as fluorine surfactants, although some silicone surfactants rate as “borderline persistent.”
Both silicone and fluorine surfactants are outlawed under the stringent Australian provisions.
“Australia observes what they call the Precautionary Principle,” Hubert said. “Anything that is persistent and man-made is bad because we don’t know the accumulative effects as we go from generation to generation.” This is very conservative but may indeed have some merit.
Fluorine free foam has other drawbacks as well. Formulating demands a higher quality and larger variety of raw materials, Hubert said.
“Formulating an AFFF involves 15 to 20 hydrocarbon surfactants that can be chosen from and may be six or seven fluorosurfactants that can be chosen from, plus an organic solvent and some inorganic salts,” he said. “The tub of typically used raw materials is pretty small.”
The tub needed to formulate the materials for fluorine free foam would be “as big as this room,” Hubert said. The variety of materials needed becomes a factor in compatibility with fluorine free foams of a different brand.
“You’re potentially going to be locked into a particular brand for a long time,” he said.
In the question and answer period following Hubert’s presentation one audience member said companies with fire brigades are already writing policy covering the transition to fluorine free foam.
“They are making the transition in their apparatus first,” the questioner said. “They are going to allow us to keep C6 on hand but only for bread and butter type fires. For process unit fires they are making the move to fluorine free on the apparatus.”
In turn, the change in viscosity is causing problems with strainers, suction lines, metering valves and foam calibration, he said.
Fire chiefs, Hubert said, have slowly lost the power to make decision such as the choice of foam to purchasing agents, environmental officers and lawyers. The solution may lay in becoming increasingly specific when drafting product specifications.
“I don’t have a good answer other than to make the specifications as tight toward the one product you want so you can exclude the others,” he said.
In conclusion, Hubert urged industrial firefighters to transition out of C8 foam products regardless of regulatory requirement enforced locally. Retired C8 stock should be treated as hazardous materials and either incinerated or sent through an activated charcoal carbon bed.
As to the choice between fluorinated foam and fluorine free foams, the solution may lay in adopting a dual approach for foam inventory.
“Position the fluorine free foam in areas where the hazard is likely to be a spill fire scenario,” Hubert said. “Fluorine free is attracted to oils while fluorinated shed them. Spill fires lend themselves better to fluorine free foam than fuel in depth fire.”
Switch out end-of-line discharge devices to air-aspirating devices if you use fluorine free foams so as to minimize fuel contamination. Likewise, consider using fluorine free foams in state-of-the-art foam chambers on fuel storage tanks.
“This device minimizes the amount of plunging that the foam will see while giving you protection to achieve better foam run on the fuel surface,” Hubert said.