Foam amplifies the effectiveness of water in fire suppression by breaking the surface tension, making the droplets smaller, and enhancing cooling of the water. Foam suppression systems can be messy and require special strategies and considerations for clean up that other systems do not need. In this video, fire protection expert Lee Kaiser discusses foam suppression systems, the major characteristics, and applications they are most commonly used for.
Lee: "Let's change and talk about foam systems. Foam makes water better at doing its job. It breaks down the surface tension, makes the droplets smaller, and helps enhance the cooling of the water that we're using to extinguish the fire. To make foam, we use water, add foam concentrate and air, and mix those three together to get a finished foam solution that we can apply in different ways to extinguish fires.
The different types of fires that we can deal with, there are Class A foams out there. A lot of municipal fire departments use those to help extinguish house fires. Class B foams used for flammable liquids like this picture here. This is a tank outdoors burning something, and this man is using a medium-expansion foam system to put a foam blanket on top of that burning tank. We can also use Class B foams to extinguish flammable gases. We're not going to talk about that a lot, because a lot of times gases when they light on fire, they go boom.
Liquid petroleum gas fires, when you have a pool of liquefied petroleum that is off-gassing and those vapors are burning, we can actually use a high-expansion foam system to extinguish that type of fire, so that's a neat application typically done outdoors in a pit where you've got a spillage or runoff from a large bulk LPG tank.
Systems types, depending on the amount of air that we mix into the foam, low, medium, and high-expansion foams. We can have foam water sprinklers inside of buildings, just a number of different options for foam systems. We could spend all morning talking about that, but we're going to choose to move on, talk about some of the characteristics of foam systems. We typically need a large water supply and a large flow rate for a foam system, especially when it's outdoors. You'll see, at industrial sites that use foam, large water tanks just to support the fire water system. The cleanup effort can be pretty extensive. If you discharge a foam system indoors, it's a lot like trying to clean up soapy water.
Today's foams have low toxicity. There's been a recent change in the industry to make the foams that we use today less toxic to humans. Over time, the chemicals in foams will not build up in human bloodstreams, but frankly, a little insider secret is those foams today are a little more toxic to wildlife, even though they're less toxic to humans. This brings me to my next point: it's really important to control the runoff from a foam discharge. We don't want it to be able to go into storm sewers and then into waterways. We don't want it to go to sewer systems.
We really want to pay attention to containing the foam onsite so that we can clean it up. This really should be thought about as an additional cost for your fire protection system; all the extra plumbing and drainage that you need to do to contain it and then treat it onsite. You don't want foam running off into the city sewer system because the foam concentrate itself, as it breaks down from the water, is good for the bacteria in the sewer plant. The bacteria, they're eating away at the waste in the stream of water coming into the plant, and then all of a sudden here comes some foam, and the bacteria love the foam to eat, so they start to eat and eat and eat, and you get a big bloom of bacteria. There's a ton of bacteria, and they get lazy, so they like eating the foam, and then the foam goes away once the drainage is done. Then they don't want to go back to eating their normal waste, so you can kill a sewer plant that way by letting foam get into the city sewer system, so you don't want to do that. If you're a big foam user, you should be aware of that possibility.
Foam systems are water-based systems. You've got to be aware of freezing, and then the cleanup thing. This is a great picture here. This is from a news story that happened in 2016. I believe it was in San Jose, California where an aircraft hangar had a high-expansion foam system discharge. The doors of the hangar happened to be open, so all the foam ran out of the hangar and worked its way into the neighborhood quite quickly. This is Neighborhood Joe out there swimming in the foam having a great time, and all you can really do is wait for that to drain out of the water, and then you clean up what you can, but you know some of that's going to get out of your control.