Balancing footwear function with protection
Footwear must not only protect against hazards, it must also allow for appropriate levels of agility and comfort
In our previous article, we addressed issues related to gloves and how tradeoffs exist between performance and functionality. In this column, we examine the same concerns for firefighter footwear. Generally, there are fewer issues for footwear than there are for gloves, primarily because it is easier to achieve more robust protection of the feet compared to the hands (it is not necessary to insulate each toe the way each finger must be insulated for gloves). Nevertheless, there are still aspects of footwear use that must be considered, not all of which are addressed in NFPA 1971, the standard that covers protective footwear for structural firefighting.
Currently, a number of performance requirements are applied to firefighter footwear in NFPA 1971. Whole footwear is tested for heat resistance, flame resistance, overall liquid integrity, and electrical insulation.
Footwear seams are evaluated for liquid penetration resistance (against fireground chemicals like battery acid, gasoline, and hydraulic fluid) and viral penetration resistance (for assessing leakage of blood and body fluids that may be contaminated with pathogenic organisms such as Hepatitis).
The upper portion of the footwear is tested for radiant heat resistance, conductive heat resistance, cut resistance, and puncture resistance.
The toe section is evaluated for impact and compression resistance.
Footwear soles are tested for puncture resistance, abrasion resistance, conductive heat resistance, and slip resistance or traction (the puncture and heat conduction tests are different than those applied to the footwear upper).
The shank (a metal or composite piece providing stiffness between the front of the heel and the back of the forefoot in the sole) is tested for bending resistance.
Hardware is tested for corrosion resistance, and eyelets and stud hooks, if present, are tested for detachment strength.
Thread is tested for melting temperature.
Footwear labels are evaluated for legibility and durability.
There are also several design requirements for firefighter footwear. Footwear must have a sole with a heel, an upper with a lining, an insole with a puncture resistance device (a metal plate or composite layer set above the outer sole) and a permanently integrated impact and compression resistant toe cap (may be metal or composite). As of the last edition, the footwear must be at least 10 inches high as measured from the inside of the footwear with the insole in place to the highest point on the boot where there is continuous liquid protection.
NFPA also specifies that a certain range of heel breast angle be used (this is the interior angle formed between the heel and the sole), that no hardware penetrate from the outside of the footwear to the lining (to act as an avenue for heat conduction or liquid leakage), and that nails or screws must not be used for attaching the sole to the boots.
Lastly, NFPA 1971 requires that manufacturers make available an extensive set of footwear sizing with unique sizes for men and women including half sizes and a minimum of three widths over the range of sizes 5 to 13 for men and sizes 5 to 10 for women. This sizing design requirement is the most extensive footwear requirement outside of the military for work-based footwear.
Range of options
It is well established that the firefighting protective ensemble takes a variety of forms with each of the available products offering different advantages and disadvantages. Even with the design requirements, manufacturers have the latitude to pursue different designs and choices of materials. Conventionally, there are rubber boots and leather boots. There are also some boots that combine different materials such as leather and durable fabrics.
There are a number of different lining materials, barrier materials, closure options, and methods of construction. All of these attributes provide the fire service with a multitude of choices for footwear that conform to the NFPA 1971 standard; but this does not mean that all types of footwear protect firefighters to the same level or even offer the same levels of functional use. Further, there are different preferences for footwear by individual firefighters with some aspects of NFPA 1971-based performance being addressed well, some not so well and others not at all.
Generally, there are no complaints about the levels of insulation provided by footwear, which in turn are affected by the tests in the standard that set minimum protection requirements. While a slip resistance is applied to footwear as part of NFPA 1971, there are concerns that the test and criteria do not do what they are supposed to do — ensure appropriate levels of traction for firefighters on slick surfaces.
Consequently, some work is ongoing by the responsible committee to identify a more suitable test that better ranks footwear for its traction consistent with field observations. As an example of footwear attributes where there are no requirements, nothing in the current standard addresses the functional performance of footwear as is done for gloves (such as dexterity and grip testing).
Functional footwear performance is a legitimate concern for firefighters. Footwear must not only protect well against different fireground hazards (heat, flame, electrical shock, liquids, pathogens, and the physical environment), but it must permit firefighters to be active with appropriate levels of agility and comfort.
Footwear that does not fit well or is not comfortable will create problems. Many firefighters do not wear their footwear continuously over long periods of time, but some responses may require wearing footwear for an extended duration. It goes without saying that footwear should not chaff firefighters' feet or legs and should not cause blisters. This is one of the reasons why NFPA dictates a diverse range of sized footwear be provided to the fire service. But like regular shoes, various firefighter footwear products fit individual firefighters differently.
An important aspect in the fit of footwear is ankle support. Good ankle support helps to alleviate potential injuries caused by stepping on uneven or sloping surfaces, activities that are a routine part of firefighting (stains and sprains remain the highest proportion of all firefighter lost time injuries). Different footwear types provide different degrees of ankle support based on the inherent design of the footwear and its ability to properly fit the firefighter. Yet, prescribing ankle support in footwear is not easily done.
Footwear weight is another factor. As expected, heavier footwear will put a strain on the wearer, potentially leading to earlier fatigue and changing the gait of firefighters as some recent studies have suggested. Still, the specification of weight alone cannot address this issue as there are several factors that can affect footwear imposed stress and firefighter agility. For example, the flexibility of the materials, the actual footwear height, traction as imparted by the outer sole and tread design, and individual firefighter coordination can all have a bearing on this aspect of functional performance.
Finding the right fit
Short of each fire department field testing footwear choices, one way to address functional footwear performance that captures some of the factors affecting footwear performance may be through a repeatable laboratory test. A proposal has been put forward to create an "agility test" for footwear in a manner similar to the "dexterity test" that attempts to capture functional aspects of glove design and performance. The test involves test subjects wearing firefighter footwear and running an agility course. The times for completing the course are compared with the times that the same subjects gain on the course while wearing running shoes. Larger percentage differences in the times mean that the firefighter footwear being tested causes a loss of normal agility that would be provided with a well-fitted, lightweight athletic shoe. Thus, in comparing one type of firefighter footwear with another type, the footwear exhibiting the higher percentage change would be considered to having the least desirable impact on firefighter agility.
While this test approach in no shape or form represents fireground activity, nor is intended to, it is an attempt to find a repeatable and controllable means to discriminate footwear design issues that contribute to firefighter agility consistent with the experience of firefighters. Preliminary attempts at using this test have shown that the test ranks footwear consistent with how firefighters perceive differences in different product agility and functional performance on the fireground. These results further show measured differences between products to be significant. If further proven out, this test as a possible requirement in the NFPA 1971 standard could become a tool when combined with practical aspects of footwear performance that helps manufacturers improve footwear design towards more form fitting, comfortable, and functional boots.
No test can replace direct assessments of the product under the conditions of actual use. Fire departments and firefighters should judge for themselves which products provide the right combination of performance and functional use. Nevertheless, the requirements in NFPA 1971 are intended to set the minimum requirements for footwear that guarantee baseline protection and functionality. By setting minimum requirements in NFPA 1971, fire departments and individual firefighters are then free to choose the products best meeting their needs. Moreover, it helps those organizations that simply don't have the resources or ability to run their own evaluations. An attempt to address functionality as part of footwear requirements in NFPA 1971 will help in this regard as it provides a consistent measurement technique to help assess footwear impact on individual firefighters.
In closing, we want to thank our readership for their thoughtful comments and insight. We do appreciate your continued interest and suggestions on the many issues we raise in our column.