How to Use Firefighter Protective Clothing Reinforcements
It makes good sense that some parts of turnout clothing are thicker and include additional materials than other parts of the garments. The collective term for these additional materials and layers is reinforcement. Garment reinforcements are used for a variety of functions that include providing additional insulation to heat transfer, absorbing shock, and protecting primary clothing layers from abrasion and other forms of physical damage. All firefighter protective clothing includes several types of reinforcements in their designs. Industry manufacturers offer a wide range of reinforcement materials, designs and placement. This article describes the most common make-up and use of reinforcements in turnout gear.
Additional layers of material must be sewn or attached to the knee area of pants. These layers are intended primarily to provide additional insulation from heat as the firefighter's knees are usually oriented forward towards the fire in a crouching position. The bent orientation of the knee results in the garment composite materials being pulled tightly against the knee. This action removes some of the trapped air between garment and skin or underclothing diminishing the insulation for this area of the body. Knee reinforcements also provide padding to physically protect the knee when kneeling on rough surfaces. The weight of the firefighter and his or her equipment will greatly compress this area of the garment. Moreover, as a firefighter crawls over a chaotic fireground environment, the knee areas of the pants will generally take some of the greatest physical abuse.
Garment manufacturers offer different types of reinforcements. In general, these reinforcements consist of an outer material placed on the shell of the garment and an additional layer of insulation material that is placed on the liner. Additional layers of different materials can be placed on both shell and liner. For example, insulation material can be placed directly beneath the outer reinforcement layer, while additional layers of insulation material are often used on the liner. The more layers of additional material used as part of the reinforcement, the more overall insulation is provided. However, the number of layers and the materials used in those layers have to be considered for their impact on firefighter mobility as affected by the overall stiffness of the reinforcement. Furthermore, different materials have different characteristics in terms in physical toughness (durability), retention of insulation properties, and comfort.
There are a variety of materials in use for both outer covering and insulation. Extra layers of outershell material may be used as the outside layer of the reinforcement. There are also a number of coated materials that can be used, which offer puncture and cut resistance and lessen effects of water absorption that may be associated with some textile materials. However, there is some concern that heavier coated materials may have the drawback of storing thermal energy due to their greater density. Leather has also been a commonly used outer reinforcement as a result of its relative toughness and resistance to abrasion, but can become stiff with use and may accumulate some types of fireground contaminants. For insulation purposes, extra layers of thermal barrier materials (the inner most layer on most turnout clothing) are used most often. Different manufacturers offer a variety of related padding materials and non-textile products, all with the goal of providing extra insulation. In addition to layering, some manufacturers offer different types of knee constructions that may create more trapped air or permit portions of the reinforcement to be removed for separate cleaning or replacement.
Areas of reinforcement
The knee reinforcement is usually sized such that the reinforcement will stay on top of the knee with all wearer movement, particularly when the knees are bent. NFPA 1971, the standard that governs the design and performance of turnout clothing requires that knee reinforcement measure at least 6 inches by 6 inches on each knee. However, it is not uncommon to see knee reinforcements range from 8 to 10 inches wide and 8 to 12 inches high.
Another mandatory reinforcement area is the shoulders of the coat. Like the knees of the pants, the shoulders are oriented towards the fire. Due to the weight of the SCBA on the firefighter's back, the harness straps compress the clothing materials against the top of the firefighter's body. Therefore, additional insulation is needed on top and to the front and back of the shoulders. Nevertheless, industry practice and NFPA requirements do not dictate the same levels of insulation on the shoulders as provided on the knees. In general, at least one additional layer of outer shell or thermal barrier is added to provide the needed insulation. Still, manufacturers offer a wide range of insulation designs and materials to meet the demand for more insulation, some with features that minimize the amount of compression that takes place between the multiple layers of the reinforcement. NFPA 1971 requires that this reinforcement measure a minimum of 4 by 4 inches square on each shoulder, though many manufacturers offer clothing designs that extend this insulation to greater distances along the crown of the shoulder and extending a greater distance down both the front and back panels of the coat. Some designs include extended insulation down the top of the arm as well.
Elbows, another juncture of the coat where compression takes place, can also be reinforced. There is no requirement for their reinforcement, but typically, an outer patch of leather, textile shell, or coated shell material is placed on the exterior. These outer layers may be further supplemented with an additional insulation layer added to the liner and aligned so that the reinforcement stays over the wearer's elbow went bent.
Reinforcing materials are typically placed in several other locations of the clothing, though these features are not mandated by the NFPA 1971 standard. The edges of pants hems and sleeve hems are generally reinforced as these hems face constant physical abuse during wearing and many textile outer shell materials will fray. Hem reinforcements are thus applied to extend the life of the garment and prevent tears and abrasion at sleeve and pant ends. Additional reinforcement materials are also used along closures such as the front closure of coats and the fly for pants to likewise keep materials from fraying. The waist area is often doubled or strengthened with different materials to provide an anchor point for suspender hardware. Reinforcements are also used underneath hardware, particularly hooks and dees that secure the front closure of the coat and pants. These extra layers, generally outer shell or leather pieces, provide a more stable surface for hardware attachment and prevent the hardware from ripping out of the clothing prematurely. Reinforcements may be used underneath pockets where tools might be carried, or in any area where there are concerns for additional wear and physical damage to the overall clothing.
How to use reinforcements
Reinforcements should be used judiciously. The addition of extra materials and layers, while increasing thermal insulation, also creates penalties in terms of extra weight, bulkiness, and stiffness, depending on the location and choice of reinforcement materials. Moreover, some combinations of materials may not have the desired effect. For example, the use of very dense materials in the creation of reinforcement for insulation purposes might actually have the opposite effect. It is also important that the reinforcement maintain its performance qualities. While the abrasion or physical damage for an outer layer may be readily apparent, the separation of reduction of thickness for an internally located padding material may not be readily detected and can lead to less insulative performance than expected by the firefighter.
The chief insulation test for determining the effectiveness of the reinforcements in NFPA 1971 is the conductive and compressive heat resistance or CCHR test. This test is used for evaluating the shoulder and knee areas of fire fighting protective garments. The test evaluates shoulder and knee areas under pressure (2 pounds per square inch for shoulder areas and 8 pounds per square inch for knee areas, simulating the weights of the SCBA on the shoulder and the pressure exerted by a kneeling firefighter on the knee). Testing is conducted with a sample representative of the reinforcement placed on hot plate set for a contact temperature of 536 F. Testing is performed under both dry and wet conditions. For the wet condition, the lining portion of the reinforcement is exposed to a mild wetting technique prior to testing to simulate the accumulation of moisture on the interior of the clothing. A calorimeter that is constructed to measure heat transfer in a manner similar to skin is then used to measure the time for a 43 F (24 C) temperature rise to occur (called the CCHR rating) after the sample is placed on the hot plate. NFPA 1971 requires that the CCHR rating be 25 seconds or greater. Unlike thermal protective performance (TPP) testing where the TPP rating is associated with a predicted time to burn injury under very specific conditions, the CCHR rating only provides a means for comparing different reinforcements and is not related to burn injury prediction. Consequently, higher CCHR times indicate better conductive and compressive heat resistance.
Although reinforcements are an important feature of turnout clothing, providing additional insulation at shoulders, knees, and elbows, the utility of reinforcements should be carefelly weighed on several factors. Namely, what are the effects of additional layering on the individual firefighter and what is the expected performance, durability, and overall impact on the clothing. Fire departments should examine reinforcement needs carefully, gaining an understanding from other departments' experience with particular reinforcements and examining how current clothing holds up in needed areas of insulation and physical reinforcements.