Before going out into the field to stop a wildfire, firefighters must get their gear together. Temperatures are going to be high, visibility will be low, and a lot of debris will get in the way. Firefighters must have the right gear, but how does this gear actually work and protect them? Read on to learn more about the three different layers of firefighter turnout gear.
What Is Turnout Gear?
Turnout gear, also known as bunker gear in some instances, is the PPE firefighters wear when working with fires. These fires are so high in temperature that firefighters must wear specially designed clothing that can stand up to the heat. Within the turnout gear, there are three different layers: the outer shell, the moisture barrier, and the thermal liner. This three-layer composite was invented over 100 years ago, and while the technology has improved, the principal function of each layer has remained the same.
The Materials
Before going into the specific layers of firefighter turnout gear, it’s important to emphasize the different materials the layers comprise. You can’t use fabrics that will melt and burn you in the heat, but you also don’t want to be suffocated when out in the field. The manufacturers behind this gear tried to find the right balance between breathability and safety, and they’ve found the perfect materials to do so. The flame-resistant fiber blends that these manufacturers work with are:
- Flexible
- Sturdy
- Not too heavy
- Abrasion-resistant
- Durable
All the materials that a manufacturer would use in their turnout gear are also certified by the National Fire Protection Association (NFPA). There are strict regulations that the manufacturers must follow to ensure that the wearers are safe when out in the field with these fires, and they achieve that safety with a blend of fabrics like KEVLAR, PBI, and PBO.
The Outer Shell
The first layer of defense from fires is the outer shell. This barrier protects the wildland firefighters from the direct flames and heat they’ll be working around. What’s most important about this gear is its thermal protection and high limiting oxygen index (LOI). If the LOI was lower, the polymers in the outer shell could potentially combust as it only takes a small concentration of oxygen. High LOIs will protect the wearers in the field from having their turnout gear catch on fire.
This outer shell also protects firefighters from cuts and abrasions, which is a common hazard of working in the field. When firefighters are around a wildfire, they can get cut by a variety of debris, like tree branches. If any part of their gear gets cut and opened up, it could lead to disaster. That’s why protection from cuts can sometimes be just as important as the fire resistance in a piece of turnout gear.
Most of these outer shells are made of a PBO, KEVLAR, and PBI blend, all of which have very high LOIs. Depending on the function, there are different kinds of outer shells with different fiber blends, weights, and weaves, impacting their ability to work in higher temperatures, flexibility, and durability. These shells are incredibly protective, but they suffer wear and tear after every trip out into the field. They will eventually break down from flame exposure and suffer embrittlement, potentially exposing the wearer to the flames.
Thankfully, you can look out for some signs to protect yourself before this occurs. Dye sublimation occurs when the dye in the shell dissipates, typically at around 450°F. The shell is not compromised at this point, but it is a good warning sign that you should check your layers to ensure everything is still intact.
The Moisture Barrier
In addition to the outer shell, the moisture barrier does a lot of work at protecting the wearer when putting out these fires. Because wildland fires can be so unpredictable, firefighters find themselves in a lot of weird places and situations, and they need to be protected from everything. This moisture barrier is the second layer of protection and can protect the firefighter from all kinds of liquids, including the following:
- Chlorine
- Battery acid
- Gasoline
- Fire-resistant hydraulic fluid
- Antifreeze
Firefighters won’t encounter some of these too often, but protection against any of these liquids is important. In addition to protecting from these dangerous liquids, the moisture barrier allows firefighters to perspire freely. This breathability arises by wicking the moisture away from the wearer, something incredibly important when working around such extreme temperatures. Sweat is a common side-effect of working in these extreme temperatures, but the moisture barrier helps to keep that under control.
The moisture barrier is a Polytetrafluoroethylene (PTFE) permeable film barrier and is laminated to a flame-resistant substrate material. It is a critical barrier to protect the firefighters in the line of duty, but this layer is also one of the more fragile ones. In addition to going out and combatting these fires, the firefighters must also spend a lot of time inspecting their gear, like the moisture barrier. They do this to ensure it works as it should and provides the proper support needed when in the field.
The Thermal Liner
The thermal liner is the final layer in turnout gear, but it is just as important as the other layers. This layer does the most in terms of providing thermal protection from the fire heat. It does this by trapping air between layers of material. If the liner were the only part of the turnout gear, it wouldn’t be the most effective, but with the other layers, it can protect the wearer in even the harshest conditions.
These liners typically consist of a face cloth and non-woven batting that are comfortable and flexible enough for the wearer to move in them easily. The face cloth is normally made of fibers spun like cotton, a fishing line, or a combination of the two. When the fibers are composed of mainly filament, like a fishing line, they can slide easier against your body, whereas the cotton form can bunch up easier.
These three layers of firefighter turnout gear all work together to protect the wearer from even the hottest flames! However, while this equipment is important, it’s not the only thing that wildland firefighters wear. They also need to wear wildland fire hard hats, masks, gloves, pants, and boots. We have all the equipment you could ever need here at The Supply Cache!
