Fire Retardent Paints. Flame-retardant intumescent coatings provide precious time in the event of a fire. When exposed to flame or extremely high heat, the coating layer expands and produces a char, which insulates the surface and helps keep oxygen -- necessary for combustion -- away from the substrate.
by Susan Brimo-Cox
, every second counts. These extra seconds can mean life or death, and in some instances, can determine whether a structure is savable or a total loss.
There are many materials and coatings that can slow a fire. Kenjay Williams of PPG Industries, which makes a variety of fire protective coatings, points to cementitious and subliming coatings; dry insulation, such as rock wool or gypsum board; and intumescent coatings as examples. For our discussion, it’s the intumescent coatings we’ll concentrate on.
How do intumescent coatings work? A chemical reaction takes place in the coating when it is exposed to flame or extremely high heat. The coating layer expands and produces a char, which insulates the surface (helping to keep it cooler) and helps keep oxygen — necessary for combustion — away from the substrate.
This chemical reaction can offer minutes of extra time in the event of a fire. Intumescent coatings are available in different formulations from a variety of manufacturers.
Exterior intumescent coatings are typically epoxy-based, Williams says, offering good corrosion resistance and less weight than cementitious coatings. Epoxy intumescents are used in the petrochemical industry for exterior applications on refineries and offshore platforms. Because they are known for their impact strength, adhesion and resistance to humidity, they are also being looked at for some interior applications, such as swimming pools, clean rooms and high-rise structures, Williams adds.
Epoxy-based intumescent coatings require a thick-film application, usually by licensed applicators. They are typically applied at 100-500 mil thickness, typically use fabric or steel mesh reinforcement for longer ratings and have a more textured surface finish than thin films, Williams says.
Interior thin-film intumescents can be vinyl- or water-based and provide a paintlike finish. Some are designed to be used on exposed interior structural steel where a paintlike finish is desired. Others are designed to protect interior wood, drywall and other substrates. You’ll find these used in many commercial environments, such as office buildings, health care facilities, multifamily housing units (such as apartments and condominiums), hotels and restaurants, and schools.
Thin-film intumescents can be spray-applied using airless equipment. The specific coating thickness depends on the product being used and the specified fire rating.
According to Jim Raby, who’s in charge of technical service sales at Flame Control Coatings LLC, different localities set their own minimum requirements for fire ratings. A municipality can’t set a rating lesser than the state-mandated rating, he says, but if it meets or exceeds the state regulations, a municipality is free to set its own.
Much testing has been done relating to fire and flame spread, and there are a variety of laboratory tests that flame retardant coatings must pass in order to be rated. ASTM, Underwriters Laboratory and other industry-specific agencies generally conduct the testing.
Fire retardant coatings aren’t used very often in single-family homes, but it wouldn’t be a bad idea.
Jake Clark, owner and president of Armstrong-Clark Co., a California-based exterior stain manufacturer, has developed an exterior flame-retardant stain he has confidence in, but he faces a challenge. “There is no test criteria for the aftermarket in California for exterior products,” he says. So he has created his own tests, using roof shakes, wood siding, wood fences and a wood deck, with the goal of having burning embers burn out in place without spreading.
Bill Hendricks, owner of Safer Building Solutions, does a lot of work concerning wildland-urban interface and agrees that there are no fire retardant testing parameters for exterior paints and stains. He says the problem with using interior flame retardant products on the exterior of a home is that they don’t hold up to weather. (As far as he knows, no interior flame retardant product has passed the accelerated weatherization test.) Some possible remedies are to use an oil-based product or encapsulate it; still, “a product may be flame retardant, but how long it will last is the uncertainty,” he says.
Beyond thin-film fire retardants are products that provide fire resistance. More than a matter of semantics, fire resistance relates to penetration of flame versus spread.
Steve Beck, president of International Fire Resistant Systems Inc., explains the difference: At the lower end of the scale, flame retardants generally need to pass a flame spread test. At the high end they pass what is referred to as the room corner tests, where they also test for flashover and smoke. But, not only do flame resistant products need to pass the room corner tests, they need to pass a fire penetration test, too. The added protection of preventing fire penetration for up to two hours preserves the structural integrity of a building, he says. Beck already offers an interior fire resistant product that applies like paint, and he is working on an exterior-use version.
The important thing to remember when selecting a fire retardant or fire-resistant product is to make sure you are getting one that does what it promises. Ask the product manufacturer for the testing certification documentation. If they won’t provide it, look elsewhere. And make sure the tests passed measure up to the fire rating standards you need to meet. “There is a lot of misconception out there,” Hendricks says. “You really need to look at how the testing is done.”