|It may come as a surprise but the majority of firefighters have not read a very important document in regard to their personal safety.|
It is the instructions that come with every set of firefighter personal protective equipment issued to them. Ask the following questions to another firefighter and wait for the awkward silence to end:Have you read the instructions on your turn-out gear (PPE)?
- Do you know the limitations of your turn-out gear? Your pants, coats, gloves, facepiece, and SCBA?
- What is the TPP of your gear?
- What is the THL of your gear?
- When was the last time your PPE was inspected for damage?
- Why is this important to firefighters?
There are defined limits to the protection a protective ensemble can provide. A firefighter’s P.P.E. reduces their risk of burns and injuries by absorbing and releasing heat. However, P.P.E are not indestructible shields from all fireground elements. FEMSA advises, “Be constantly alert to the possibility of exposure to radiant, convective, or conductive heat and other hazards.” (Within the PPE User Information Guide on page 2.) I
It is also recommended that you be consistently aware of your surroundings for exposure to radiant, convective, or conductive heat and other hazards (FEMSA User Guide p.2-4). For firefighters to be consistently aware of their surroundings for exposure to these particular elements; they must first understand how their senses have been deprived of being able to recognize these elements.
So, let’s pose the question: How well do firefighters understand their PPE? And more importantly how do firefighters measure heat?
Today’s modern fire environment consists of engineered materials in construction filled with higher heat release content fuels that demands a diagnostic tool that allows firefighters to prevent thermal insult, identify and locate the fire’s severity, and locate any victims or firefighters in danger more quickly than ever before. The victim trapped inside of a fire is not afforded the luxury of a SCBA and modern firefighter P.P.E to protect them. And in studying and training internationally, we have witnessed a common and disturbing trend.
Many firefighters base their need to flow water on whether or not they feel heat. When a firefighter crawls through a 300-degree Fahrenheit room on the way to the seat of the fire they would often say, “I didn’t open the nozzle because it wasn’t that hot.” However, an unprotected victim lying in that environment would beg to differ with a firefighter’s subjective definition of “heat.” Those who advocate that firefighters should wait to feel the heat to indicate their level of safety should read and remember the following:
A firefighter’s protection within the confines of their P.P.E is determined by many factors and variables. However, the ability of a protective garment to withstand a specific level of heat until it is saturated to the point of the individual receiving a second-degree burn is known as TPP.
What is TPP?
TPP stands for Thermal Protective Performance as it equates to our PPE’s ability to protect us to the point at which our bodies receive a second-degree burn. This is often associated with the thermal insult that occurs during flashover conditions but TPP is much more complex than this. It is the rating on how long a firefighter can operate in a specific thermal environment based on temperature, heat flux, and duration of exposure and the overall condition of his or her PPE.
Thermal Protective Performance is based on the work of Alice Stoll. In 1967 in a study performed by Alice Stoll and Maria Chianta, the women lined up and physically burned a group of young sailors on their forearms! They recorded the temperature and time at which the men responded to the pain. This was performed across a range of radiant heat fluxes, and the burns that developed blisters after 24 hours were recorded as second-degree burns. This is how second-degree burns became medical terminology, as they previously weren’t quantified.
Firefighter’s need to understand that when their P.P.E is saturated with heat or their TPP is exhausted, the heat will then transfer to their bodies resulting in the following:
- At approximately 131 degrees Fahrenheit, a firefighter will experience bee sting like sensations which is known as “Alarm Time.” This is the body’s way of warning an individual that they are being burned or about to be burned. It is important to note that this is when a second-degree burn occurs but the pain threshold is actually much lower than that. If this direct contact continues to a human body for more than 30 seconds, two-thirds of the burn damage will occur after the heat source is removed.
- At approximately 140 degrees Fahrenheit, a firefighter’s pain receptors are turned off as a protective mechanism.
- At 162 degrees Fahrenheit direct contact, human skin is destroyed.
Therefore, the old tactic of waiting until a firefighter feels pain is not an empirically adequate nor recommended tactic for gauging the overall thermal severity of the environment. As late as 2016, there are still fire service “textbooks” that recommend using their ears, their wrists, or penciling the ceiling to gauge thermal severity. All of which have been disproven as a means to gauge thermal severity. In addition to this information a firefighter’s P.P.E must be a minimum TPP of 35 which equates to 17.5 seconds of protection in flashover temperatures until they receive a second degree burn. However, even with TPP ratings as high as 60 in some firefighter gear, it is critically important for firefighters to understand the power of the following on how we reduce our PPE’s overall effectiveness by any of the following preventable factors:
- Dirty Gear: Dirt/Soot
- Wet Gear (Perspiration included)
- UV Damaged Gear
- Prior Burn damaged (thermal bruising to the moisture barrier)
- Saturated Gear (with thermal energy due to failure to properly cool the environment)
Dirty Gear vs Clean Gear
Firefighters across the nation are washing their gear regularly and even in certain departments these firefighters are issued two sets of gear. In the past, dirty gear was seen as a badge of honor and now it is seen as a badge of cancer. As FDNY’s new contaminant reduction program states “Clean is the new Salty.” Dirty gear not only continually exposes the firefighter to carcinogens and unknown chemicals absorbed from the incidents they face but it also greatly diminishes their level of thermal protective performance in a fire.
The contaminants found on PPE from various incident exposures can gradually break down the fibers in the gear. Dirt and contaminants should always be removed from PPE at the earliest chance possible to keep it from abrasive wear.
Dirty or contaminated gear therefore lessens the overall thermal protective performance of the garment which reduces the firefighter’s ability to withstand super-heated environments. Dirty gear also inhibits the reflective quality of any of the reflective stripes added to their PPE.
Wet Gear: From the Inside…
Fire departments who purchase firefighting turn out gear often choose higher TPP over many other variables, which in many cases comes with lower THL (Total Heat Loss). Lower THL comes at a price by added cardiac stress to firefighters. Why? Higher THL allows the heat from a firefighter’s body to be lost through the gear. In the past, firefighters could not purchase higher TPP gear with also high THL. With advances in today’s technology that is no longer the case.
Higher THL allows for less cardiac stress on firefighters. What is not often considered is the increase in moisture content due to firefighter perspiration in regard to reducing the amount of time a firefighter receives a second degree burn. Therefore, a high TPP test on a mannequin that doesn’t perspire isn’t truly indicative of how a human body would react. Water has the highest thermal conductivity of any substance (with the exception of helium and ammonia) which allows heat to be transferred to human flesh faster than dry skin. “Recent studies have shown that moisture, present in firefighter turnout systems, has a complex influence on heat transmission and potential for skin burn injuries [1, 2].” When firefighter PPE is exposed to sweat (between 1.5 liters to 3 liters per hour) there was an overall reduction in thermal protection in low temperatures by as much as 10 seconds or greater (p 31). In these tests, they also showed that “moisture negatively impacts protective performance most severely when the added amount of moisture at a comparatively low level such as 15 to 20 percent of the turnout system weight (p.31).
And the other issue that is overlooked is cardiac stress to firefighters. Heat stress contributes to heat stroke, cardiac fatigue, and cardiovascular failure. In addition to this data, heat stress is attributed to over 50 percent of firefighter line of duty deaths.
In many departments across the country, we see a common trend of a gross-decon or bucket washing of their turn-out gear after a fire due to lack of availability of gear washing system. Although this isn’t harmful to the gear and is recommended, what happens next is often detrimental to the TPP of the gear. Firefighters will hang their gear to dry outside in the sun. UV damage can diminish the level of thermal protection available to firefighters upon their next exposure to heat. This is due to photo-oxidative reactions which deteriorate the fabric.
Prior Burn Damage and Saturated Gear:
The Minimum Thermal Protective Performance of turnout gear provides 17.5 seconds of protection before a firefighter receives a second degree burn in flashover temperatures. This is the rating is for brand new PPE which is 35. What level of TPP does your PPE provide? And the proper care of our PPE extends our levels of protection or can diminish it if we fail to maintain it properly. If a firefighter’s gear has been damaged due to multiple exposures to fire, they are unknowingly facing an enemy that will have an even greater advantage upon them in the next battle. A firefighter’s gear needs to be inspected regularly and after each fire. A firefighter should look for damage to the outer shell, moisture barrier and thermal liner. Such damage is shown in photo number five.
In addition to this data, the human body receives a second degree burn at approximately 130 degrees Fahrenheit direct contact and at 140 degrees Fahrenheit; the human body’s pain receptors “are turned off” thereby preventing firefighters from feeling any pain or heat at above this temperature. The current TPP of today’s turn-out gear is often so high that firefighters do not feel any heat until their gear is saturated with energy. Firefighters can no longer completely determine the overall thermal severity of the environment based on their senses. As shown in photo number three, the firefighter’s gear is saturated with heat and will eventually transfer this heat to the firefighter’s body. Therefore, newer PPE that combines higher TPP and high THL offers the benefits of both worlds: overall good TPP and higher THL which reduces cardiac stress to firefighters. This also allows firefighters to feel heat again at lower levels whereas certain gear manufacturers over build their PPE to such a level that firefighters are completely unaware of how severe the environment they’re in.
As we mentioned, we cannot totally rely on our pain receptors to determine overall level of safety but our body has a natural warning system known as “Alarm Time” which begins to warn us of an impending burn. At approximately 113 degrees, our body feels pain. Higher TPP with Higher THL offer the best protection while still allowing firefighters to feel certain levels of heat. As a wise firefighter once told me, our senses should not be completely removed from us. If we ignore the information presented here and continue onward with ever increasing levels of TPP completely encapsulating the firefighter from their environment we will continue to see firefighters injured due to burns and overexertion.
As the FEMSA manual states: “Burns are a function of time and amount of heat transferred to the body. You can be burned in relatively low temperature environments. If your protective ensemble is exposed to heat or flames long enough. Similarly, you can be burned over a very short period of time if your protective ensemble is exposed to relatively high temperatures. Heat can build up and be stored in your protective ensemble element to the point that where your skin burns. Your skin burns at temperatures far below the burning point of your protective ensemble.” (FEMSA User Guide p. 2- 4).
Therefore, there has never been a greater need for firefighters to be trained in understanding fire behavior, thermal severity, and how to interpret this data through tactical thermal imaging, better understanding of their PPE, and by continually educating themselves on the challenges of the modern fire environment that we face today.
Firefighters need to understand that their fundamental skills are their foundation but when working in near zero visibility environments with the best gear produced to date, their senses are actually diminished. A thermal diagnostic tool in well trained hands that understand the advantages of proper interpretation can aid in preventing thermal insult to the victim, further damage to their property and lessen or prevent thermal insult to firefighters.
Keep learning and stay Intelligently Aggressive.
T&L Equipment Company. The Dangers of Unclean Firefighter Turnout Gear. Retrieved from: https://www.washcycle.com/dangers-uncleaned-firefighter-turnout-gear/
R. L. Barker,1 C. Guerth-Schacher, R. V. Grimes and H. Hamouda ( Effects of Moisture on the Thermal Protective Performance of Firefighter Protective Clothing in Low-level Radiant Heat Exposures. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/29283320/
Retrieved from: https://journals.sagepub.com/doi/pdf/10.1177/0040517506053947
Shonali NazarÃ©, Rick D. Davis, Jyun-Siang Peng, Joannie Chin (2012). Accelerated Weathering of Firefighter Protective Clothing: Delineating the Impact of Thermal, Moisture, and Ultraviolent Light Exposures. NIST Technical Note 1746. Retrieved from: https://www.nvfc.org/wp- content/uploads/2016/08/NIST-Report-on-Accelerated-Weathering-of-PPE.pdf
Definition: Alarm Time: This is the time between feeling heat (alarm) and the onset of a second degree burn. Feeling pain or heat on your skin does not necessarily mean that you are burned. You may still have time to remove yourself from the heat source or reduce the heat before getting burned. The time interval between feeling the pain or heat and getting burned is called “alarm time”.