The protection offered by your turnout gear is predicated on the ensemble being worn by itself. NFPA 1971, the standard by which the minimum design and performance of the turnout clothing is established, does not account for what clothing or undergarments are worn in conjunction with your ensemble.
In fact, it assumes that you may be wearing nothing underneath your ensemble. This is a clear departure from the historical consideration of work uniforms and other clothing that was, at one time, included as part of the protective package.
Certainly before most fire departments adopted full bunker clothing in the late 1970s, firefighters relied on their uniform pants to complete part of the protective envelope in addition to long coats and hip boots.
There were even earlier versions of NFPA 1971 where the uniform pants could be considered part of the overall lower torso and leg protection for the purposes of meeting some requirements. However, even as the fire service protective clothing standards have evolved, it can and in some cases does matter what you wear under your turnout clothing.
So, if turnout clothing is designed and certified to protect firefighters by itself, then why does it matter what you wear underneath this clothing? After all, there are some parts of your body that will generally not be covered by anything else but your protective ensemble.
These areas include your arms if wearing a short sleeve shirt, your lower legs if wearing shorts, your neck depending on the style of shirt you are wearing, your face, head and your hands.
The protective ensemble elements that cover your body in these regions are the sole difference between your being protected or not. However there are those that raise the concern that what you do wear can be a problem, and it is possible and sometimes has happened that clothing items have contributed to injuries subtained by the firefighter.
This is why many believe that garments worn under your turnout clothing can create problems if not properly selected.
The question of what to wear beneath your turnout clothing has been a perennially debated issue in the fire service. When the NFPA 1975 standard on station/work uniforms first came out, it mandated the use of flame-resistant fabrics in the construction of uniforms.
Originally, while uniforms were not primary protective clothing, it was believed that in some circumstances firefighters could be exposed to flame and heat and should always be in some type of flame-resistant clothing.
However, back in 1999, NFPA 1975 was revised to permit either 100 percent cotton, 100 percent wool, or materials that were flame resistant as demonstrated by flame resistance testing.
The rationale provided for the change at the time was that the non-melting characteristics of fabrics were considered more important than overall flame resistance, but that interior clothing should not add potential danger in the event of an extreme thermal exposure.
Soon afterwards, the committee responsible for the 1975 standard found that it was more desirable to use an actual test that demonstrates safety from melting, rather than specifying cotton and wool, and eventually developed a thermal stability test that is now part of the standard.
In NFPA 1975, materials cannot melt, drip, or ignite when exposed to high heat. The new test evaluates if fabrics will stick to surfaces or potentially to skin. Flame-resistant garments remain an option, and are still specified by many departments that have determined that flame resistance is an important uniform attribute for their firefighters.
The basic sentiment is that firefighters should not wear any uniform clothing that contains thermoplastic materials such as polyester and nylon because these are capable of melting and contributing to burn injuries
It is argued that this should not matter, because if the temperature at the uniform level reaches the temperature needed to melt polyester or cotton (above 450 F), then the turnout clothing is severely compromised anyway.
While that may be true, we have noted in some post-incident clothing evaluations that polyester-based fabrics underneath turnout clothing does melt if it takes a large localized heat exposure. There are plenty of fabric alternatives which will not melt under these conditions.
The design requirements of NFPA 1975 specifically exclude its application to underwear. Nevertheless, some departments have instituted the same practices for using products that do not melt and are recommending that their members not wear nylon, polyester, or materials with high contents of thermoplastic materials.
Requiring members to wear 100 percent cotton gets around the issue of discerning the safety of blends and other materials. This would seem a reasonable approach but is very limiting, and it is expected that cotton this year will be ramping up in price to nearly 80 percent over its current cost.
When it comes to general clothing materials, some fire departments and individuals are intrigued by the new material technologies that promote good moisture management.
The thinking is that moisture under the garment in some circumstances can also contribute to burn injuries since wet gear can be more conductive than dry gear.
We have learned that the role of moisture in clothing is very, very complicated and there are no easy answers. When it comes to the role of moisture in clothing, its effect on protection depends heavily on the conditions of use, including the type of heat exposure, the length of the exposure and exactly where the water is located in the material system.
In some instances, water can provide a degree of cooling; however water can also act as a conductor and as a heat sink, so the level of heat transfer and its rate are critical in determining whether there will be adverse effects or not. Unfortunately, there are just no definitive answers to this issue.
We do believe that 100 percent polyester, nylon, and other fabrics with relatively high thermoplastic fibers should be avoided and should be part of standard operating procedures until additional information becomes available.
What we do not know is what percentage of these fibers constitutes a hazard, other than relying on the current NFPA 1975 test, which at this time only addresses uniforms.
Our hope is that future research will begin to shed light on these issues and help direct the fire service to better understanding of what should be worn with full confidence underneath your turnout clothing.