By Collin Hofschulte
After teaching a PPE and SCBA familiarization for a Firefighter I class, I realized that I needed to focus on a key question: What is the main purpose of our turnout gear?
Firefighters can think of turnout gear from a few different perspectives – limitations, capabilities or both. When I was a new firefighter, I considered my turnout gear only in terms of its limitations. But as I gained more experience operating in fire buildings, my perspective changed more to a more capabilities-driven mindset.
The oven mitt analogy
When a firefighter enters a structure fire, they are essentially mimicking a person wrapped in an oven mitt and placed into an oven set to broiler. The insulative material of the oven mitt reduces the transfer of heat from the outside of the mitt to the inside of the mitt. When we wear turnout gear, the concept is no different. If one purchases a thicker oven mitt, it will take longer to transfer the heat to the inside. If the oven mitt is thinner, skin will burn quickly.
With that as our backdrop, it begs the question: What type of burn does the fire service deem unacceptable? The answer is second-degree skin burns.
No matter what kind of turnout gear you have, it will have a thermal protective performance (TPP) rating. Think of TPP in the context of time. The higher the number, the more “time” one has inside of the oven mitt before becoming burned. As the TPP number increased, so does the insulative properties of the turnout material. A lower number means fewer insulative properties. If we placed two mitts into the oven at the same time, with the same temperature, both oven mitts will sustain burns if we do not remove them. But the mitt with the higher TPP number will not become burned as soon as the other.
What does this mean for firefighters? TPP ratings are equivalent to the time it takes to receive second-degree skin burns under flashover conditions.
Temperature vs. calories/BTUs
Taking this one step further, the question becomes this: How much heat causes a second-degree burn to humans? It’s easy to think in terms of temperature alone, but this could be misleading. Temperature is a momentary measurement of molecule vibration or invigoration, measured in degrees. Temperature gives no environmental context. We all know that it takes time to heat something up, so we must also consider heating in the context of time. Additionally, we must look at the size of material we are heating.
Calories and British Thermal Units (BTUs) are measured by the total amount of heat transferred to a specifically sized surface area. This is also known as heat flux. It takes 1.2 calories/cm2 to deliver a second-degree burn on bare human skin in about 1 second. When measured with a calorimeter, heat flux measurements are plotted on a graph, over time. Measurements are displayed as the heat flux curve. By cutting swatches of turnout gear, and heating them up, manufacturers can test the “human body side” of turnout gear in a controllable manner, revealing the burn injury time. The burn injury time is then translated to a TPP rating.
Bottom line: It is the speed at which temperature rises within the turnout gear that is of greatest concern.
Flashover math
In fire academy, we were all taught that flashover situations are the deadliest fireground hazards – but this is without context. Past research has found that flashover usually occurs at heat flux levels anywhere from 20-200 kW/m2. While this range is quite wide, the American Society for Testing and Materials (ASTM) chose a number somewhere in the middle, 84 kW/m2. When converted, this is the equivalent to 2.01 calories/cm2.
How does a firefighter know when the environment reaches 2.01 calories/cm2? Experience. The only way for firefighters to know what this level feels like in a fire environment is through the use of tried-and-true techniques, such as reading smoke and fire conditions and understanding one’s body amid heat conditions. Some math helps, too.
Calculation: Divide turnout gear TPP by calories/m2 to estimate the amount of time it will take to receive second-degree burns. If my TPP rating is 35, it will take me 59 seconds to receive second-degree skin burns at 0.59 calories/m2 or 25 kW/m2. If my TPP rating is 35, it will take me 17.4 seconds to receive second-degree skin burns at 2.01 calories/m2 or 84 kW/m2.
Perceived limitations and personal responsibility
Back to the original premise – how we perceive our gear. I believe that the uncertainty of time and temperature on the fireground has been translated to the fire service as a “limitation” of the gear. But the reality is that it’s up to us – the firefighters – to understand how much time in the heat is acceptable before it causes second-degree burns.
Furthermore, while my turnout gear may certainly protect me, I would like to believe that SCBA and turnout gear were invented so that victims could be given the highest probable chance of survival. We enter fire buildings, even under the most uncertain and punishing conditions, to rescue victims. This is because firefighters are sworn to protect and serve the community. After all, even before the invention of SCBA and turnout gear, firefighters would risk their lives to rescue victims from smoke and heat. Now we can just do so with better protection, at a greater distance into the hazardous environment, meaning more time to make a save.
Maximizing our capabilities – for THEM
When considering whether your turnout gear allows you to increase your capabilities in the fire environment, ask yourself these questions:
- Are firefighters spending more time standing safely on the outside of a burning building spraying water, with their turnout gear on, because the fire is dangerous to US? or
- Are firefighters entering occupiable spaces as soon as possible to search for victims, with their turnout gear on, because the fire is dangerous to THEM?
If turnout gear is simply accepting the energy given off by burning material in a structure fire, then by understanding heat transfer and TPP, we can guide firefighters in making crucial moves on the fireground, for THEM. Certainly, I am not advocating for firefighters to walk right into a room of fire; no victim will likely be alive here. However, at every fire, we must still look for areas of the structure to occupy because turnout gear and the human body gives us the capability to make entry. Turnout gear is only as good as its operator. As skin is heated under the protection of turnout gear, we must understand how to interpret these sensations and translate it to intelligent, critical action. Our training and level of skill follow.
Bringing it all together
Are we spending enough time understanding how our body operates on the fireground in turnout gear? Is the capability of my body in good enough shape for the citizens?
TPP standards are based off heat performance, not individual body capability. How heat affects my body will be different than yours. Understanding one’s body, and turnout gear, is a victim-conscious opportunity that must be seized.
Also, do not forget that SCBA facepieces and portable radios may fail earlier in the process than turnout gear, but many times, there are preceding signs to warn of this impending event (e.g. rollover, worsening smoke conditions, increased sensation of heat, distressing radio traffic, structural failure). I might only have 10 seconds or less to occupy a space before leaving, but that is 10 seconds given for potential victims as compared to not entering at all.
Speed and efficiency in various fire techniques will impact your time in dangerous fire environments. The time it takes to find a victim is essential to survival – we all know this. If I am assigned to search during a residential home fire, I will likely not use the protection of a hoseline because this would significantly reduce my speed. But, because I understand this, I know that I must protect myself with other means (e.g. staying low, isolating spaces, closing doors, using water cans). Just because I don’t have a hoseline doesn’t mean I’m limited; it just means I must understand my capabilities without it better. In these times, I understand how much heat energy my turnout gear and body can withstand when searching. And ultimately, faster and more thorough search techniques will limit my heat exposure.
Victims require firefighters who can make tactically appropriate choices based on our capabilities, not limitations. Experience and training in turnout gear, SCBA use, and fire environments will increase our comfortability to make these victim-conscious choices.
Be honest about your ability to maneuver inside of fire environments. It can make the difference for a victim.
ABOUT THE AUTHOR
Collin Hofschulte is a career firefighter and medical coordinator, providing EMS training and education to over 135 staff members with the City of Duluth, Minnesota. He has served in various educational roles since 2020, first as a paramedic preceptor for Mayo Clinic Ambulance and later as a fire instructor II for Fire Instruction & Rescue Education and the Duluth Fire Department. Hofschulte serves as a principal for the NFPA Technical Committee on Emergency Service Organization Risk Management. Hofschulte is an alumnus from Mayo Clinic School of Health Sciences Paramedic Program. He has an associate degree in liberal science from Riverland Community College as well as a bachelor’s degree in fire administration and a master’s degree in fire executive leadership with a concentration in human resource management from Columbia Southern University.