As the foaming systems manager for, Clarence Grady knows his way around firefighting alternatives to water. He served as both a career and volunteer firefighter before entering private industry in the early '90s, as more and more fire departments began using Class A foam.
You have a long history of developing foam systems. Can you clear up some misconceptions about foam and firefighting?
I come out of the hardware and application side of things, so to the largest extent I could choose to put whichever foam in the hardware of the company I'm with, so I get a lot of questions on which foam to use.
There are a number of water additives or foam agents that are being promoted as universal foams that will handle Class A fires, Class B fires and some even say Class C, which is electrical fires and is insane because you never do electrical without depowering, then it reverts to A or B or D, which is flammable metals.
Some folks promote the use of their material on flammable metals. The problem with flammable metals is that they're very water-reactive. They create a heat reaction to them to extract the water and break the water back down into hydrogen and oxygen components. You get a really big boom when they go back together.
There's been a lot of testing on metals over the year — castings with no surface area. People overwhelm them with massive amounts of water until they've gone out. They hit so hard that the cooling effect stops them without too many of the hydrogen releases.
Where would you find those kinds of metals?
Castings in the automotive areas. The old Volkswagen air-cooled Bugs used to have some really wild fires because there was an aluminum-magnesium casting back in the trans-axle and motor. When it really got going good, the crew would put a little water in and you'd see something, but when you hammered it, it would go out.
What are the problems or limitations with universal foams?
The problem I have with the universal foam people is that I would almost go on record that they're not the greatest students of fire itself and exactly what these fuels are. For instance, flammable metal chip fires. If you take anything water-based and spray it into those, you stir them all up and — oh man! — it looks like fireworks!
There's a group of people out there offering these universal agents, and they're claiming they work on anything. The metal castings or metal chips may not be a big issue, but at what point will one of these universal agents get someone in trouble in a Class B fire, which is a flammable liquid, that will run into gasoline, hydrocarbon families or clear to a pure alcohol? With the emergent technologies of ethanol, we're going to see more of the pure alcohol and that's going to be problematic for people with Class A foams. They better be looking for their B. What happens is that the foam concentrates tend to be more soluble in the concentrates than in the water. So you put a known alcohol-formulated foam on it and it goes away. Nothing happens for a short time, then oops, we're in trouble!
Some of the universal foam [companies] are proffering their stuff is good for that, but what we find is that the material is a Class A foam, and maybe not even a good Class A foam but more of an emulsifier. They're not suitable in most any way, shape or form for Class B at a large scale, where you “oops” and you need a Class B. They're not any more suitable than if we'd stayed with known Class As like Ansul Silv-Exes and the Angus products that have been around for a long time.
Everybody in the fire service, including me, would love to have one magic-bullet foam that would do everything. The problem is that when you analyze the chemistry of the fuels you want to put out, it becomes clear that that can't happen.… How could there be universal foam unless they could turn something off catalytically in the formulation?
What we find with a universal foam is it's an emulsifier — a detergent — and that's pretty easy chemically to do. The [aqueous film-forming foams] will pass the B test like UL 162 or a fluorocarbon. Fluoro-hydrocarbons are tougher to make and a lot more money. If you are going to be a B foam and certify it to UL 162, that's a hell of a test to pass because you have to foam it out in a minimum period of time. Plus, once it's out you have to wait a certain period of time to see if it burns again.
With UL 162, you have two minutes at two gallons a minute to put out a 50-square-foot pan of heptane, which is a repeatable fuel that is just as ornery as gasoline. You wait and those bubbles better not pop, because in seven and a half minutes we're going to see if it burns again. Not only put it out, you have to keep it out. Tough test, and there aren't a lot of agents other than the mainstream foam companies and a few small companies that have been able to get a UL 162.
How can a fire department find out if the foam is legitimately certified?
Ask the person who is trying to sell it to show which test it passed. I've had some real interesting experiences with people saying they had universal foam. I had one say their foam was usable at 0.5%, 1%, 3% and 6%. I told them to make their choice, because if it's Class A foam, it's 0.5%.
There is an old standard out there called NFPA 18. It was a flammable liquid test for foaming agents, but it was for the 1950s wetting-agent foams and predecessors to the Class A foams when I got involved. There's a major difference between a 2gpm nozzle to do UL 162 and the 10gpm nozzle for NFPA 18.
In both tests, you start with a certain amount of fuel floating on a certain amount of water and that gives you a fire to fight. In 162, you have two minutes to put it out. In 18, all you need to do is put it out before the pan overflows, and there's quite a bit of free board on the pan, like 5 or 6 inches. If you can put the fire out before it barfs over — because of the way NFPA 18 was done — you can pass. And there was no burn-back test.
A customer has to push: “What standard was it tested to?” and the company should be able to produce a UL 162 listing.
In flammable liquids, you can only have two percentage numbers. It's legal to have two numbers. You can have a lower number where you can pass UL 162 for hydrocarbon heptane, and then there will be a higher number where you can pass the same test with polar-solvent fuels. Once we know if we have a hydrocarbon-class fuel or an alcohol fuel, we look at our buckets. If it has a single number that doesn't mention alcohol and we think the fire's alcohol, we may as well do nothing, because we're screwed and it's not going to work! Protect exposures, but if we don't have alcohol-resistant foam, we're not getting it if it's a large-scale fire.
What do we do? Do what you need to mitigate risk or life hazard. If you have one of the cans with two percentages on the can, you can run at 3%; you figure out what it takes to run, hopefully, if it's going to take a lot of foam.
Is UL 162 a more accurate test?
For a flammable liquid, by far and away. You can actually take any good dish soap and a good foaming nozzle and it will go through NFPA 18. Application rate comes about in the field. When we need to develop a flow, and it might be 100gpm per 1,000 square feet of fire on something that's a cross between fuel and depth, that's liquid standing pretty thick on pavement. It might come up to 160gpm if the fuel is deeper, or if it's alcohol it might be 200gpm.
A car fire isn't really a B fire to the greatest extent, because it's rubber, plastic and it's Class A — kind of a B with melting plastic. But what if the gas tank blew up? It's only 18 gallons and only 50 to 70 square feet, that's nothing.
What guys found is that they come in with their modern-day engine with their Class A foam similar to these universals, and they can get off with a large engine and a handline and just annihilate this thing. Geez guys, you had a little old car fire that could use a .02 application rate and you pounded it with a .20!
Because we have readily available, push-button foam, we've developed a big application rate because it's on our preconnects. We don't use the B foam because the A puts everything out situationally. The average fire department doesn't go to a tanker [fire] every day, and many departments never had one. How many departments don't even have tank fires?
Do most trucks usually carry Class B foam?
According to ISO, a truck had to carry foam. At the time the standard was written around 1982 and published in '84, we still hadn't resurrected Class B foam, so it just said “foam.” They haven't changed, so a truck has to carry foam according to ISO. So if it was a car in a garage that popped a fuel line, how big of a fire could that really be? Since they seemed to be hammering things to death with Class As at the time the standard was written, there was no distinction.
The fire departments, depending on where they are, end up getting away using Class A on first-due, day-to-day engine company runs. There's nothing wrong with that. Some of the bigger departments will come around a corner and — oh no! — they aren't going to have enough Class B foam. The NFPA standard is that you need to be able to sustain your pumping time for 15 minutes. It's not going to take 15 minutes to put it out, but you're going to get it wrong the first time, so you have to have enough foam to do it again. Once you put it out, you have to keep it out.
When you begin to look at a foam tank on a pumper, even a Class B tank may not do real good on the big one. Twenty gallons of Class B foam on something really big is laughable. You'll have to go to mutual aid and you better know where all the B foam is and how to get it there, get the application ready and do it right. It takes huge amounts of foam.
On a tanker rollover at a couple thousand square feet, everybody and his dog can do 200gpm and do it off their Class A units, but the foam is 3% foam — that's six gallons of foam concentrate a minute. Oops. Foam tank's how big, 25 to 30 gallons? Maybe you can get in there and knock it down on the foam tank, but then what? That's where you begin to look at 90 gallons of foam? By the time that incident happened and you put it out and kept it out, you're going to know where 90 gallons of foam is.
[Los Angeles] County Fire Department took some older engines that had stainless-steel water tanks … and filled them with foam. The rules are that if it's fuel of any level, send the first two engines and hem it in or mitigate the disaster until the B gets there and do it right. That isn't a terribly bad set of circumstances provided the engine companies know there's some things you better not try with that A foam.
What happens if you mix Class A and B foam?
I've seen high application rates well-aspirated where foam nozzles on the A synthetic detergent really put the fire out. Problem is going back to the native state of the chemistry: It loves the gasoline and fuel too much and the bubbles break, and you're back to a vaporous situation and could have a reignition very, very rapidly. If that's all you've got, and enough to keep reapplying until you get the B there, it'll work.
That's one of the things I see in general on Class B. People realize that they might need B, but aren't prepared to have enough of it and don't know how far it will or won't go. Class A has muddied the water because people think it will work, but there will be a certain fire in scale where you're not going to get away from it. Somebody asked me about a 100-gallon semi diesel-tank fire. Diesel is a combustible, not a flammable. You have to virtually preheat it to make it burn. At the application rates that are out there today, Class A will smash diesel and again; it's only laying a very thin layer on pavement. They'll say, “See, we don't need that B.” Again, you didn't today, but you have to figure out where you are at jeopardy for B….
What happens if someone starts to put Class A on a fire, then finds out it's really a B fire?
You can put any of the Bs right over the As and it hurts nothing. The major thing you can't do is to mix the two concentrates while you're putting them on, like into one tank.… They turn into Jello, and that's really bad.
Alcohol-resistance foams have a chemistry that forms a plastic-like polymer to try to create a physical barrier, like Saran Wrap. Unfortunately, the really good Class A foams have alcohol in their formulation to make them emulsify and penetrate. So you put A and B by accident and see what happens: The B foam sees alcohol and then you get this glop. There's a series of other mistakes that could happen.
What are gels in relation to foam?
Welcome to the '70s. The gels have been out there forever. They've been in a dry powder form, which is their native chemistry state. It's a big long chain of dry powder molecules, like the material that's in baby diapers, that holds all that water. They are a water-absorption material and have been around a long time.
The Bureau of Land Management in the late '70s and '80s worked with a product called Gel-Guard, and it's exactly what these new rebirth gels are in one form or another. BLM had that and tried to use it in desert fires. What they found was that if the water was gelled up, it wouldn't really last a long time because the polymer didn't want to retain the water longer than the dry air or the wind or even the wick-effect of the fuel wanted to put it in the fuel. When you had this water completely coating the fuel, then when fire-heat hit it, there was a really weird set of physics. The water was really so close together it was like trying to boil a pan. You can put massive amounts of heat to the pan, the metal puts the heat in the water and the water completely sinks the heat away and nothing happens for a long time. That's what gels can do.
When gels came back out in the '90s, everybody was big-eyed. Because mineral oil suspended the stuff the BLM had, it was so slippery when you got it on the top of the vehicle, you had people sliding off the vehicles on top of cactus. It wasn't a sport that was going to catch on! … What if the guy couldn't read directions and doubled or tripled the mix? Well, it got so thick the water tank turned into a tub of grease. It was a good thing they had removable lids because you had to shovel it out. To this day, it's the same thing with gelling agents.
What's the future for gels?
It's fascinating to see what they can do to or with fire. I've done some low-level experimentation, but I have not been able to figure out field application as yet. I would like to inject them back into the vehicle and have them come back out the nozzle just like normal, but what we see people having to do now is use a nozzle proportioning product.makes a nice little item. The Pro-pak is a nozzle with a jug on the end of it, gel agent in that and it comes right out at the end of the nozzle. It's a little clunky and you're limited to a gallon.
Is this used as a preventive measure?
Right. I cannot conceive — and I'd like to test — an extinguishing enhancer. The detergents are very good at that. I can't see how it's doing things physically that it would be, so they are in a defensive operation. In an urban-interface situation we can slime up the houses, but maybe the mineral oil and the slime we use will interact with the roof and tar and cause issues or peel the paint. There have been some issues with foam where they saved the guy's house but it peeled the paint and the guy turned around and sued the Forest Service. Well, your house is still left!
The gels are here, but they are defensive urban interfacing: a fire repellent. They are hard to handle. I've tried to handle this stuff since the '90s when the product Barricade was first introduced. One of the things we found is that if you try and keep something from getting water around a fire truck, it's guaranteed that water will get in. As soon as water gets into this stuff — poof! — it sets like a gel shampoo. Oops!
We tried to use a foam-proportioning system like a gel-proportioning system, and we found a way to get water into it, either because when we washed the proportioner out we used water or we blew it out but still had some water. It didn't work. Then we tried a “virgin” proportioner, and it would proportion the material fine, inject it into the hose stream and we got some nice looking gel. Well we put the nozzle down and ogled the gel for five minutes. If the gel on the fuel got hard and we didn't stop the unit before we put the hose down, the stuff in the hose was gel. Oops.
We could open the nozzle, and it would extrude this gooey stuff and eventually started flowing again. Unfortunately, we found out that the hose we used had a rough lining, like forestry hose, and the stuff stuck to the hose liner. As we continued, the flow got lower and we thought something was wrong with the pump. Our poor 1½-inch hose got arteriosclerosis and choked. The whole shebang was plugged up. Somebody mumbled “flush it out,” and some guy who was with us hit the flush valve on the foam proportioner while the goop was in there. We plugged that thing so royally, we took a day to ream it out of the hoses because it does what it's supposed to do: react with water. Oops. By the end of this voyage of discovery, we had a lot of fun looking at gel and fire…. It was fun to do the research.
Some folks say they have a new system that is more benign, and what I think they've done is retard its timing. We need that stuff to set up really quick after it gets out of the nozzle. If they've done one thing to the physics, I would like to look at [gels] again.
There was a display at a trade show recently where a company stirred up some foam at 9 a.m. and it was still foam at 4 p.m. Foam versus gels?
I like wet fuel. That's why CAFS is still king of the hill on urban interface. If you get in and get it right, lo and behold the thing didn't burn because CAFS can put the water in, soak those fuels up so deeply and store a little water up until it's wet fuel.
What we see with the gels, they'll stay there for 18 hours. It's the quest for the Holy Grail. To this point, we haven't found a great hardware package to make it field-usable, so you can have a tank and a rig and the average operator.…
It's not dumbed down, but it better be reliable. If we can do this and go into foam-dependent tactics, which means I'm going to go do this because I have foam in my hose line and it's going to put it out, but if the foam goes away, that old factor of 2-to-1 — foam is twice as good as nothing in the water — if the foam goes away, what do we do now? We've suddenly become dependent on it.
Some days we were apprehensive about going in, but now, modern day, we're getting more reliable. We're doing things that depend on this subsystem of the fire apparatus — the foam — and it's working. On balance the systems work. The gel is such a cluster to handle, I have no qualm that they tell you about the finished product over there, I just can't get the finished product over there in a state that isn't hard to use. The ProPak-style machine worked [in our tests], and maybe that's as good as it gets.…
Final words on foams and gels?
… There is a degree of use of Class A foam on a Class B fire. If we look at data sheets, they do mention using these on hydrocarbon spill fires, which is like a car wreck of a certain scale. Obviously, they know it will work up to a certain point, but you're never going to say that's your only foam like the universal foam guys say you can.
Another thing that irks me a little is that a few of the people that sell the Class Bs say, “Go ahead and put the B on the A.” Yeah, it's going to be better than nothing in your water, but I don't know if I want to use it. They say run it at a really low percentage, but it's never been tested for surface tension and things. I will admit it's better than nothing in the water, but it may not have been what you came here for if your primary protection is house fires and car fires.…
When you analyze the fire problem, you've got to decide what you're going to use, and the bulk of the people are going to be running a good Class A. With the number of car fires that they run on, I'm going to say it's going to be enough. But what they need to do is not abandon the B in any way shape or form, but get enough. They've never had enough B, but be ready to deliver a B to the big one and they'll be just fine.
Chemical Properties of Foams
|Class A Foam||Class B Foam|
|Carbon-attractive: Material is prone to migrate toward the fuel||Carbon-shedding: Foam tends to stay away from the fuel|
|Low water-surface tension promotes spreading and wetting||Low water-surface tension promotes spreading and allows film of solution to form over fuel|
|High detergency emulsifies oils and waxes to allow wetting||Low detergency resists fuel pickup|
|High foamability||High foamability|
|High environmental degradability||Moderate environmental degradability|