The Retardant Revolution
- February 14, 2024
- 9:03 am
Iain Hoey
Share this content
Fortress North America sheds light on how it is merging tradition with advanced fire-retardant technology
In an era marked by unprecedented wildfires, the necessity for progressive firefighting solutions has never been more pronounced.
Fortress North America (Fortress), an industry leader in fire control, is making significant strides in this domain by reinventing fire retardants.
In this article, Jenny Hood, Head of Fire Retardants, Bob Baird, Director for Governmental and External Affairs, and Joe McLellan, Senior Director of Innovation, delve into Fortress’s evolution, the groundbreaking science behind their magnesium chloride-based retardants, and the exceptional features that set them apart in the realm of fire suppression.
Fire retardant evolution
Until Fortress entered the fire-retardant industry, fire retardants really had not evolved much, if at all, for the last 20 years.
And while our company doesn’t offer wildfire control or mitigation strategies, we do produce and safely deliver next-generation fire retardant products that help manage the spread of wildfires.
The strategy and operational decisions on a fire are determined by the incident commander and his or her team.
With respect to the evolution of retardants, going back to the beginning in the 1960s, there was a lot of attention focused on ammonium phosphates – and these materials are still predominantly used in the market today.
Early on, there was also some use of borates followed by a period of ammonium sulphate use, but those materials have essentially been out of use since about the turn of this century.
There also has been an evolution in the colour packages from iron oxide to more current fugitive approaches that fade with UV exposure from the sun.
Fortress uses a high-visible magenta colour to help firefighters in the air and on the land see where fire retardant products have been applied.
The concept of fugitive retardants has been around since the early 1980s. There have been minimal significant advances in thickeners with the biggest being the transition from clays to gums.
Additionally, there has been a desire on the part of many stakeholders to improve acute aquatic toxicity and to reduce overall toxicity, especially with regards to heavy metal content.
Fortress entering the market with an entirely new chemistry has been a huge change for the fire-retardant industry.
The initial products from Fortress have focused on formulations based on magnesium chloride (MgCl2) – a naturally derived salt extracted from mineral-enriched brine using solar evaporation.
The Fortress formulations not only have a lower carbon footprint, but lab tests show they help set new standards in terms of low aquatic toxicity while being highly durable and effective.
While there may be certain niche market applications where ammonia-based retardants make sense, MgCl2-based retardants that offer lower environmental impact should be the primary fire retardant used.
Addressing legacy retardant issues
Legacy retardants have an ammonium phosphate base. Concerns with phosphate-based retardants include aquatic toxicity and the fertiliser effect.
When dissolved in water, ammonium phosphate will dissociate into ammonium and phosphate species.
The ammonium will then form an equilibrium between the charged ammonium form and the neutral ammonia form based on the pH of the solution.
Even at very low concentrations, ammonia is highly toxic to aquatic species and should be used sparingly in certain applications.
The second area of concern is the way phosphates impact the environment they are introduced to.
The build-up of nitrogen and phosphorous nutrients in water ways can lead to eutrophication, where the overloading of nutrients can result in toxic algae blooms with the potential for fish kills and other damages.
On land, the application of phosphates in wildlands can promote the growth and spread of fire-prone invasive species, such as cheat grass.
These species have shallow root systems compared to more drought-tolerant and fire-resistant native species.
The shallow root systems of invasive species intercept water before it can reach the deep roots of native species increasing the drought stress on those native plants.
The invasive plants with their shallow roots are then less resistant to dehydration – as the summer heats up and the soil begins to dry out, they die off early in the season and create light and flashy fuels that are prone to ignition.
Fortress FR-200 for example, is our flagship liquid concentrate retardant based on magnesium chloride.
It’s ammonia-free and has the highest LC50 of any currently approved retardant on the U.S.
Forest Service’s (USFS) Qualified Product List (QPL).
LC50 is a measure of acute aquatic toxicity that the USFS uses when evaluating products – higher values mean the material is less toxic.
The active ingredient in FR-200 will not contribute to eutrophication or promote the growth and spread of fire-prone invasive species including cheat grass.
The integration of magnesium chloride
The unique chemistry of our proprietary magnesium chloride formulations brings a new and multi-faceted set of fire suppression capabilities to the frontlines of firefighting.
Fortress fire retardant products provide a thermally responsive, staged-reaction scheme that hydrates, cools, delays ignition and disrupts combustion.
Together, these reactions make for stronger fire lines and superior fire control.
Magnesium chloride catalyses low-temperature charring which reduces the availability of flammable compounds.
Charring in the presence of magnesium chloride generates an inert layer of magnesium oxide, ash, and other compounds that help inhibit further burning.
In the end-stage decomposition of magnesium chloride, chloride ions directly interfere with combusting free radicals, minimising the spread of fire.
Ensuring prolonged
Magnesium chloride is highly hygroscopic, meaning it loves water.
It will absorb water from the atmosphere when the relative humidity (RH) is above about 33% and will continue to absorb water until it forms a saturated salt solution.
The equilibrium state of magnesium chloride at relative humidities below 33% RH is that of a hexahydrate, i.e., MgCl2*(H2O)6, wherein each MgCl2 is coordinated to six water molecules.
As the active ingredient in a long-term fire retardant, the unique properties of MgCl2 shine.
When a MgCl2-basedretardant is dropped in front of a fire, the retardant will take longer to dry compared to legacy retardants holding on to “free” water until the RH in the vicinity of the retardant is below 33% RH.
Then as it “dries out” it will form the hexahydrate, wherein the amount of coordinated water in the retardant is more than 50% by weight.
These coordinated water molecules require more energy than free water molecules to drive off as the flame front approaches.
The dehydration of the magnesium chloride hexahydrate in the retardant line cools the flame front, dilutes the combustion gasses with non-flammable steam, and then reduces the rate of flame spread.
Eventually the flame front will drive off all the water and the salt will begin to break down where it can form hydrogen and chloride free-radicals that will annihilate combustion radicals in a catalytic fashion – thus disrupting combustion much like halon extinguishers.
These formulations are highly durable, too. They will not dry out and blow away. The hygroscopic properties tend to keep the retardant hydrated, pliable and in conformal contact with the fuels.
Unlike phosphates, they are not actively consumed for nutrients by plants, fungi and microorganisms.
However, they will readily wash away with winter rains and the fugitive properties mean the colour will fade away after several days of UV exposure from the sun.
Ground and aerial evolution
One of the more interesting developments in the retardant space has been the development of the new category of retardants on the USFS QPL for ground-applied pre-treatment retardants.
A significant portion of human-caused wildland fires have ignitions near roads or power transmission lines or other power infrastructure.
The new class of fire retardants can be an effective tool to help reduce those types of ignitions.
Fortress has developed several ground-applied pre-treatment retardants to address this need.
FR-600 is a MgCl2-based formulation that was specifically designed for these types of applications.
It was designed for annual application to department of transportation or utility rights-of-way in early summer as the seasonal grasses begin to turn brown.
They last throughout the summer and fire season until they are washed away by winter rains.
As mentioned earlier, MgCl2 is particularly well-suited for this application as it will not dry up and blow away, nor will it readily decompose or get consumed in the environment like other retardants.
The hygroscopic nature will serve a dual function of both dust mitigation and reducing the likelihood of ignitions in the treated areas – slowing the spread of any ignitions that do occur.
Furthermore, the non-fertiliser nature will not promote growth in the treatment areas and may decrease the need or use of herbicides in some areas.
The use case for aerial retardant applications and the resultant environmental risks associated with those applications are well defined.
This is not the case with ground applied pre-treatments.
The repeated treatment of areas is one way that ground-applied and aerial uses differ.
In aerial retardant applications, specific areas are not likely to see repeated application within 5–10-year period, whereas FR-600 and related products are designed to be applied annually to the same locations.
While aerial applications must respect a 300-foot buffer of any waterways, most roads have ditches for handling stormwater run-off and thus the implications of those seasonal treatments will need to be understood.
While the USFS conducts a national environmental impact statement for aerial use of retardants, it’s left up to the users of ground applied per-treatment products to assess the potential impact for their treatment plan in their specific area.
This is the primary challenge that has hindered the large-scale adoption of this technology.
There are several studies ongoing that are seeking to better understand the fate and effectiveness of these products.
We’re optimistic those studies will reveal positive results.
In addition to FR-600 for ground applications on roadway and utility corridors, Fortress has developed a retardant to help protect structures, which is very important for communities at risk of wildfire.
Fortress FR-700 is our long-term retardant specifically designed for structural defense.
This product also features our unique magnesium chloride formulation making it more effective, safer for the environment, and more durable than conventional, phosphate-based retardants.
Fortress FR-700 features a higher salt content for improved fire shielding and a higher viscosity mix to adhere to structural surfaces like fences, decks, siding and roofs.
FR-700 is applied directly to structures as a pre-treatment or rapid response application.
The retardant remains effective throughout the fire season.
When needed, it can be easily washed off with a hose and leaves no residue.
This product is available in a clear, colourless formulation or in a high-visibility fugitive colour.
This product is fully qualified by the USFS.
We have seen interest in this product from Homeowner Associations, FIRESAFE Councils, realtor groups and fire professionals interested in protecting communities from catastrophic wildfire damage in a more environmentally friendly way.
An effective retardant
The feedback we have received has been primarily positive.
There are not great mechanisms for conveying those insights from the field back to the manufacturers outside of the operational field evaluation.
In a specific case of ground applied retardants, we supported an application for a prescribed burn with our FR-600 product in a relatively dense area of homes and around a prison.
The fire leadership responsible for the prison was using prescribed burning to create a buffer around the facility to ensure staff and inmates can safely shelter in place.
They used our fire retardant to ensure the prescribed burn stayed in the project boundary, adding an extra layer of protection against an escape which was important with the project area being so close to a community, thereby helping make the prescribed burn even safer.
Future innovations
Fortress will continue to drive innovation in the fire-retardant space with a commitment to developing and testing highly effective fire-retardant technology that minimises toxicity and environmental impacts.
Our aim is to broaden our product offerings and continuously improve upon existing products to help keep people safe.
