Fire-resistant garments are provided to the select few who voluntarily risk life and limb and go into harm’s way. They do it to ensure the safety and security of the rest of us. In this group are members of the all-volunteer military and first responders, from firefighters to the riot control units and SWAT team in any local police force.
A government agency sets requirements for the use of fire-resistant clothing (FRC) in most established industries. For instance, workers in the oil and gas industry are governed by standards for the use of personal protective equipment (PPE) established by the Occupational Safety and Health Administration (OSHA). Its policy (29 CFR 1910.132(a)) criminalizes the failure of employers to provide and use flame-resistant clothing for personnel in production-related operations.
However, the need for fire-resistant garments is not limited to those who fight fires, do police work, or have jobs in specific industries. The need for this protective gear extends to professionals in more unusual positions such as race car drivers and movie stunt performers. In other words, any enterprise where a person faces the possibility of being severely burned in a mishap benefits from the use of fire-resistant garments.
The effectiveness of fire-resistant garments is determined by a combination of factors, including the three most important ones: the material’s physical properties, the material’s thermal properties and the structure of the total ensemble that the individual is wearing in a potential fire situation.
First, let’s get what a fire-resistant garment ensemble should not be out of the way. For example, no part of an ensemble should be composed of highly flammable or highly intumescent clothing. In the former case, the user is likely to become a walking incinerator should an undergarment or outer garment catch a spark and ignite. In the latter case, the user is likely to be squeezed into suffocation should the undergarments expand beyond the capacity of the outer garment to accommodate the increased volume induced by extremely high temperatures. Obviously, these types of garments undermine the designed functional merits of the fire-resistant outer garment.
So what are some of the features of fire-resistant clothing? Surprisingly, one of the most valuable properties of fire-resistant garments is their ability to channel moisture away from the wearer’s body; this is known as “wicking” or moisture management. A review of patents granted or applied for over the last decade reveals an emphasis on enhanced and sustained wicking effects for fabrics.
Additionally, because of advances in nanotechnology that have improved textile structural design and manufacturing, fire-resistant garments can now function as a ventilator in situations where the temperature normally causes a flash fire situation. Previously, the capillary tubes in natural fibers were placed somewhat chaotically within a fabric; today, these capillary tubes can be aligned so that fluids flow across the thickness of the fabric, causing a cooling effect for the wearer.
In an ideal world, fire-resistant fabrics need to be porous enough to allow effective ventilation but dense enough to not readily suffer structural degradation under high temperatures. They need to have sufficiently high heat capacity to absorb as much heat as possible before their molecules are rearranged; however, they also need to have low thermal conductivity to afford the user sufficient latitude to endure exposure to the widest possible range of high temperatures.
But there is no such thing as an ideal world. So given the state of the art in textile technology, it becomes all the more important that any fire-resistant material is deployed in conjunction with other fire-resistant materials so that the components of the total ensemble reinforce one another’s strong properties rather than mutually cancel one another out.
It is common knowledge that extreme heat degrades a material’s properties. Melting and complete combustion are the result of the complete physical destruction of a material. Therefore, certain safeguards must be in place to prevent the complete degradation of fire-resistant fabrics.
Moisture management is very important to fire-resistant materials. Given that most fire-resistant materials are designed to enhance the movement of fluids transverse to the surface of the fabric so that fluid is channeled away from the body of the user, it does not make sense to use non-fire-resistant garments beneath fire-resistant outerwear. Obviously, the undergarment would deteriorate under high temperatures and potentially undermine the structural design of the outerwear.
Even if the undergarment does not structurally deteriorate, the fact that it does not reinforce the designed functionality of the fire-resistant outerwear bodes ill for the ensemble. It’s important to be cognizant of the fact that in any assemblage of materials, an ensemble’s effectiveness is defined by the weakest component.
A non-fire-resistant base layer worn under a fire-resistant outer garment has the definite potential to clog up the works. In this case, the strength of the chain is truly determined by the tenacity of the weakest link.
About the author:
Carolyn Kidd is the Marketing Manager of DRIFIRE® in Chicago, IL. DRIFIRE is a leading provider and developer of flame resistant (FR) fabrics, FR garments and protective apparel to the government, industrial and consumer markets.