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BY BOBBY HALTON |
Every now and then, there’s a topic that comes up in the fire service that you absolutely have an ironclad position on; sometimes you’re the majority, and sometimes you’re in the minority. We have all been asked questions about our opinions in conversations that went something like this: “Our gear is too good; it allows us to get into places that we shouldn’t get into, and that’s the reason firefighters are getting hurt.” A derivation on that theme is, “I don’t think we should wear hoods because if it gets too hot, we can’t feel the heat on our ears.”
Officially, the unequivocal editorial position of Fire Engineering magazine is that our current bunker gear is good and we look forward to it improving. Also, we absolutely endorse wearing all personal protective equipment (PPE) correctly all the time when engaged in firefighting. That includes wearing hoods. The argument that we should be wearing gear that has less thermal protection than our current gear is flawed for several reasons. It’s important that we understand fire behavior, how our gear works, and the temperature limits a person can reasonably withstand and still be able to perform.
According to the National Fire Protection Association (NFPA), thousands of firefighters sustain burn injuries every year at a cost of between $2.8 and $7.8 billion. But, the cost is not the real issue. The real issue is the incredible amount of pain and suffering that these burn victims must endure and the shared suffering of their friends, family, and loved ones. Our bunker gear, or PPE, the official designation, is designed using a series of air gaps and layers of insulating materials to protect us from the fire environment. These protective materials store tremendous amounts of energy and, when compressed, can transfer that energy to the firefighter with catastrophic results.
Much of our gear has been designed to protect us from direct flame contact, recognizing that the most devastating burns are often the result of sudden dynamic fire behavior encapsulating the firefighter. Our gear is designed to protect us from these sudden dynamic outbursts for a very brief period of time in which the firefighter is expected to facilitate his escape.
Our thermal protection is achieved through four basic layers and air gaps: the outer shell, which absorbs most of the energy and protects us from abrasions and radiation; an air gap; a moisture barrier, to prevent the exchange of moisture between the layers and lessen the transfer of energy; another air gap; a thermal barrier, which, again, is designed to reduce heat flow and moisture from the environment to the firefighter; another air gap; and, finally, a cotton T-shirt or its equivalent.
All our gear is tested to reach what is called “a thermal protective performance number.” This number is achieved by taking our gear-clean, dry, and brand new; placing it on a thermal coupling; placing a Bunsen burner and direct flame against the gear; and measuring the temperature on the thermal coupling up to 128°F, the temperature at which skin burns. A minimum rating of 35 thermal protection performance (TPP) must be achieved for the gear to be NFPA compliant. This means that a firefighter exposed to direct flame contact in a flash fire or trapped in a dynamic fire event should have 17 seconds roughly to escape before serious burns result.
One of the problems with arguing for gear that is less thermal resistant and thereby theoretically preventing us from entering into hostile environments is the nature of hostile fire events. Most hostile fire environments are fueled by smoke, predominantly carbon monoxide, which has an ignition temperature of about 1,128°F. Second, most of these hostile fire environments do not happen incrementally or gradually; they happen suddenly and dynamically. An unexpected breaking of a window or the sudden availability of a heat flow path could raise the temperature in a compartment from 200°F to 1,200°F almost instantaneously. Wearing gear that is less thermal resistant would be catastrophic if a firefighter were caught in a hostile fire event.
The argument for not wearing hoods is flawed for basically the same reason. Incidentally, hoods are rated only to 20 TPP or about 10 seconds of exposure to direct flame. Those who would argue that our ears, which are not pop-up thermometers, are good indicators of hostile fire environments are assuming that the fire grows incrementally. This assumption came from teaching the old fire behavior model in which we had the fire growing incrementally: the growth stage, the free burning stage, and ending with the smoldering stage. Today, we know that most fires we enter are oxygen deprived until we open the front door, creating a cool air gravity current that supplies the oxygen needed by the fire. This causes the temperature to dramatically and rapidly increase, often without any warning or adequate time for escaping or preventing serious injury to that exposed skin.
The second part of the story is our ears themselves, which are predominantly cartilage and can be slow to register pain. We can all remember old-timers with the tops of their ears missing from repeated burns.
Studies are underway now to see what amount of energy or heat a firefighter can withstand and still function within our technologically superior gear. We need to know the point at which the amount of energy we are absorbing becomes too much to withstand. We must also keep in mind that our PPE is an ensemble and the weakest links are our face piece and hood, the Houston Reed hood notwithstanding. Our gear will continue to improve, our understanding of fire behavior will continue to improve, and our training will continue to improve. Our body’s ability to withstand temperature will not.
