Water has always been man's best friend for battling fire. We went from bucket brigades to horse-drawn wagons to steam-driven pumpers, and now we have fire engines that can pump over 2,000gpm. All of these advances have been to make the delivery of water easier, faster, better and more efficient for the firefighter.

There have been some great advances with water additives to help make the water last longer and work better. First was “wet water,” then AFFF, then CAF, and now we have the introduction of firefighting gels.

In the wildland-urban interface, this will allow the average engine crew the ability to protect a greater number of structures than before. An engine crew that has gels along with all of the other structure protection tools that are available can pre-treat a structure hours before the firefront arrives, retreat to safety and then return to clean up the hot spots. These gels are very easy to learn how to use. Of course, it's important to remember that gels are not the “do all” and “end all.”

Fire gels were successfully used in Alberta, Canada, on the Mitsu Lake Fire in 1998. During that fire a $60 million pulp and paper mill was saved with less than 10 gallons of gel concentrate. That same year gel saved a number of homes in Florida. Since then gels have been credited for saving hundreds of homes.

In addition to protecting structures from interface fires, gels also have been used to protect mills and log decks, extinguish tire fires, and protect exposures on homes during a regular old structure fire when there weren't that many engines available to assist. They have been applied with garden hoses, 1- and 1H-inch hoses, master stream nozzles and even dropped from a helicopter.

What is a firefighting gel?

There are three types of firefighting gels on the market: liquid polymer, powder polymer and non-polymer powder. The liquid gels are educted into the water stream, and powder gels are best when batch-mixed. It's very important to research the type of gels that are on the market, and it's a good idea to talk with users of the different gels prior to purchasing and adopting gels into your department.

The polymer gel technology allows for greater absorption of water and heat. When you introduce gel concentrates into the water stream, there's a rapid absorption of water. Once the water has gelled, it can withstand very high temperatures before turning to steam. At low percentages, this characteristic assists in a quicker extinguishment time. Higher percentages allow for vertical adhesion of water, providing greater exposure-protection capabilities.

Liquid polymer gel concentrates look yellowish and opaque and smell like mineral oil. They contain an anionic water-soluble polymer, mineral oil, water and a surfactant. The concentrate includes super-absorbent polymers in its structure, which are slightly pre-swelled by water. With the addition of mineral oil, the polymers are prevented from absorbing water further.

By mixing in appropriate water quantities, the water-in-oil emulsion is changed into an oil-in-water emersion, or phase inversion. Here the absorption capacity of the super-absorbent polymer becomes free and binds additional water. This process is noticeably accelerated by the addition of kinetic energy, such as stirring, pumping and inducing into water flow. Under normal conditions this process happens within a few seconds.

Water temperature can affect the absorption process. When the water is below 10°C, the absorption of the water may take a few seconds longer for the gel to form. A dull sheen will appear on the surface, unlike the shiny look when the water is warmer. This doesn't affect the protective properties of the gel when heat is applied.

Powder gels

Both polymer and non-polymer powder gels are mixed in a similar way; batch mixing seams to work the best. This lets the concentrate completely absorb the water needed to create the desired gel. The key with the powder gel concentrates is to follow the manufacturer's directions. It's very important to check with the manufacturer prior to diverting from the preferred method. This goes for all types of gels. You don't want to damage equipment or harm the environment by improper use.

Mixing methods

Although fire gels are very easy to use, it's important to check with the manufacturer of any gel prior to the actual use. Some of the gels have different application tools, and it would be a shame if you went to use the gel only to find that you didn't have the correct tool.

There are a few ways that these gels work: batch mixing, inline eduction and end-of-the-line eduction. Each has good and bad points.

Batch mixing

Most of the gels that use batch mixing are powder-based. Once added to the water, the pump circulates the mixture prior to application, allowing the water and concentrate to gel. Advantages include the ability to premix for air operations and perform all other mixing at the engine. As for disadvantages, the water tank may have to be cleaned out, and proportioning can be difficult if the tank's water level is measured incorrectly.

Inline eduction

Inline eduction works well if you need to deliver a large quantity of gel without a Hydro Foam nozzle or an end-of-the-line system. Most gels can be used with an inline system using a regular inline or bypass foam eductor and the procedures associated with that tool.

When performing inline eduction, you need to have the manufacturer's recommended application systems prior to use, as well as the recommended percentage setting. Useable percentages are limited, but manufacturers are constantly working on formulae to allow the use of gels with as many systems as possible.

Inline eduction can deliver large quantities and is easy to learn how to use, but cleanup of the hose and system can be difficult. Plus, you're limited to the concentration percentages that can be used.

End of the line

In my mind, the end-of-the-line system is the easiest to use. With an end-of-the-line delivery system, you bring the gel concentrate with you. Each manufacturer has its own system, and they all work well, which means there's one to meet most everyone's needs and likes.You'll need to try each system to find the one that works for you.

Percentages can be chosen by the user, and there's no hose cleanup. Unfortunately, the firefighter who is applying the gel has to carry the concentrate, and large quantities of jugs must be carried and set out for application.

Firefighting tactics

Because of gel's high cooling effect, the distance to the seat of the fire can be bridged relatively quickly. When fighting fire containing solid objects and structures, gels should not be applied as a jet, particularly for short distances, as this may cause the gel to spray off the surface. A 30% fog pattern is more effective, as the product will adhere better and larger surfaces will be covered. To treat loosely piled material, swap between a straight stream and a fog pattern to achieve an internal and external gel coating.

Larger forest fires may be fought from the air and ground. The concentration of the product should be between 1% and 1.5% to allow fir good penetration into the lower layers of vegetation. The same range of concentration is recommended when very long hose lays of 300 feet or more are used with small diameters of 1 inch or less. In this case it isn't recommended to use the gel at 2% or higher.

When creating a firebreak, the same product concentrations can be used. If applying the product by air, no higher than 1.5% should be used. This will allow the gel to work its way down through the canopy to the lower fuels. When applying from the ground a higher concentration may be used. Always start at the highest point and work your way down.

For exposure protection a higher percentage of concentration must be used: 3% is recommended. It's also recommended to coat any trees around the structure to help keep the radiant heat down. It's very important to assess the site before applying the gel.

Once you have determined what you are going to coat and how much gel is needed, you need to start with the highest point to be coated and work your way down. Coat combustible roofs, eaves, soffits, roof vents, windows, siding of all types, doors inside corners, decks, propane storage tanks, fences that are connected to the building, and shrubs and other vegetation around the building. This is just a short list of items to coat, but there could be more.

Anything that is non-combustible — other than windows — doesn't need to be coated, such as metal or composite roofing and stucco and log walls. The number-one purpose of a gel coating is to stop any firebrands from igniting the building. The coating also will help reduce the risk of ignition from radiant heat.

Application techniques

Prior to application of any gel, it's very important to test the gel on the ground first. Once you're ready to apply the gel, point the nozzle to the ground away from anything and anyone and open the nozzle until you see gel. This helps to avoid pre-wetting the surface, which will impede the application process.

The application of gels for exposure protection is very simple. With the nozzle set at a 30% fog pattern, start at your highest point and work your way down to maximize the flow-down effect. Apply gels as you would spray paint in a side-to-side motion and in thin coats to allow the gel to set up and adhere to the surface. This avoids a problem similar to when you hold a spray paint nozzle in one spot for too long. Circular motions also can be used.

More than one pass may be needed to achieve the required thickness of the gel. Pay particular attention to the problem areas such as windows, where the gel may slide off if applied too thickly on initial application. Factors such as needed protection time, outside temperature, humidity and surface being covered all need to be considered when deciding the thickness of the gel coating.

A variety of hardware can be used. Scotty Fire Fighter has created a system that can be used easily with a _i-inch hose, which allows for application by homeowners. This makes it very easy when you have a small surface to coat. It can be run off a regular house tap or off a fire pump. This system is easy to use and to clean up. The _i-inch system flows at 3gpm with a minimum of 40psi.

Scotty also has made a 15gpm system that runs off of either a 1- or a 1H-inch hose. This end-of-the-line system has been built to manufactures specifications for a set percentage, which may change from manufacturer to manufacturer. This system runs at 100psi and with an adjustable fog nozzle you have many options for stream settings.

When there's a very large application needed, such as a log deck at a mill, or a long guard is needed, the Hydro Foam nozzle can flow from 150- to 750gpm of gel. When using a Hydro Foam system, the concentrate needs to be pulled from a 55-gallon drum or a 250-gallon tote.

Cleanup crews

After application of the gel, the appliances should be cleaned of adhering gel, especially when a gel with a high percentage of concentrate has been used. The hoses, proportioner and the area of the fire (if necessary) can be rinsed using plain water. Usually several hose fillings of water are allowed to run through the hose after the inlet to the proportioner has been closed to the concentrate.

In the event of a gel concentrate spill, do not flush with water. Dam up the spill and soak up the concentrate with inert absorbent material. If liquid has been spilled in large quantities, clean up promptly by scoop or vacuum and keep in suitable and closed containers for disposal. Disposal must be in accordance with local, state and federal regulations. After cleaning, flush away traces with water.

Once the threat has passed, coated exposures need to be cleaned. If you have returned within 72 hours, it's possible to clean coated surfaces with water out of a garden hose. In fact, a pressure washer may do more harm than good. First wet the dried-out gel and let it rehydrate prior to washing off. The gel will be more transparent than the original application. If you begin at one area and work around the entire building, by the time you return to the starting point the gel will have had time to hydrate and can be hosed off very easily. If some small amounts do not come off completely, repeat the process.

If you return after three or four days, the gel should be left to dry completely and not rehydrated. As the gel dries, it turns to a dry flaky material. If you use a broom or even a rag, the dried gel can be brushed off. It should be placed into a garbage bag and taken to an incinerator for disposal.

After a rainstorm, a small amount of gel may appear in a spot that was missed during the initial cleaning. Simply rinse it off with garden hose.

Other uses

Firefighting gels have been used on many fires with great success since 1998. The use of gels to extinguish tire fires and protect log decks and mill facilities has been very successful.

Although gel technology is relativity new to the fire service, it's our responsibility to take a close look to see where each of us can use it in our departments. This isn't just a tool for structure protection on a wildland fire. If you have limited resources, gels may be the tool to use on any exposure problem. If you're bringing water to the fire via tenders, you need to look at the most cost-effective way to use that water, which may be via water additives such as gels.

Remember that a gel is just another tool in the toolbox, and you need to know when, how, where and why to use each and every tool. Gels have proved themselves to be very effective in the right situations.

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Darren Hutchinson is with Quintech Fire Services, a firefighting, consulting and training firm. He has experience as a structural firefighter, industrial firefighter and wildland firefighter.