A Multi-Layered Issue: Double-layer PPE doesn’t protect against heat injury

A Multi-Layered Issue
Double-layer PPE doesn’t protect against heat injury

By Vaughan Miller

Over the past 40 years, most Southern California fire departments that regularly engage in wildland/urban interface (WUI) structure protection operations have improved wildland firefighting personal protective equipment (PPE), going from a single layer of cotton dungarees to the standard double layer of flame-resistant Nomex. Note: Typically, a double layer consists of a long-sleeved cotton T-shirt and Nomex station uniform pants worn underneath NFPA-1977-compliant PPE. Double-layer PPE has grown popular because the idea that “more layering is more protection” has proven effective in reducing some severe burn injuries when they occur on WUI and wildland incidents.

The trouble with wearing more layers on WUI fires is that when it comes to heat injuries, the uniform doesn’t provide more protection—it provides less. Wildland firefighting requires firefighters to work under extreme conditions—from the severe external heat loads found in extreme fireline situations, structure protection and structural firefighting situations, to the high internal heat loads generated by fireline construction. As a result, firefighter heat injuries due to physical exertion, combined with the inefficient cooling of the body due to thicker PPE, have increased among municipal fire agencies that engage in both structure protection and perimeter control operations. And when fire fatalities have occurred, numerous after-action reviews have concluded that, regardless of the number of layers, PPE did not protect the firefighter from fatal injury. In fact, in one case, a double-layer uniform worn per policy contributed to severe heat injury, resulting in a firefighter fatality.

It’s important to note, however, that the cause of fireline heat injury isn’t just thicker PPE; many factors exist that increase injury risk. Fireline heat injury can occur when firefighters are simply unprepared for the work environment, and/or when the wrong rules are applied to the wrong situation. Many cases of heat injury can also go unreported as signs of injury go undetected and ignored by firefighters or their supervisors.

Despite the growing number of fireline heat injuries, many municipal departments continue to inadequately prepare their personnel and provide inflexible policy regarding PPE in dynamic fire environments. This is wholly inappropriate because each mission presents different firefighter safety risks; therefore, we must ask ourselves several questions:

•Which PPE will work for multiple missions found on WUI fires: single-layer PPE, double-layer PPE or structural PPE? Do your firefighters understand which rules apply in each situation? If so, are they prepared to act on them?
•If PPE doesn’t reduce the risk of fatal injury on WUI and wildland fires, and double-layer PPE accelerates the potential for heat injuries, why do fire agencies double the minimum standard? To reduce the risk of burn injuries? If so, is a thermal, external skin burn the most significant risk to firefighters in a WUI fire situation?
•Can we mitigate the risk(s) for burn injuries another way so firefighters can remain safe and adapt to their environment and their mission?
•Are there other, more significant risks on wildfire incidents that receive less attention, such as inhaling superheated gases, poor hydration, inadequate rest, prolonged exposure to carbon monoxide or increasing internal core temperature to the point that cardiac output cannot support the body’s internal demand for cooling?
•Have we prioritized our risks correctly when preparing firefighters for their jobs?
•Is our wildland PPE a significant, purposeful mitigation against firefighter injuries? If it is, we should add it to our 10 Standard Fire Orders and 18 Watchout Situations. If not, perhaps some are giving Nomex PPE too high a billing
•Have we prepared our employees to act so they can prevent fireline heat injury from potentially accelerating due to PPE?

In this article, I’ll discuss the potential hazards of Nomex double-layer PPE in order to demonstrate how little it actually does to protect firefighters, and I’ll show how it can work against firefighters if improperly applied to WUI missions.

External vs. Internal

Although many municipal fire agencies have doubled the legal standard for wildland PPE, there’s no conclusive data that demonstrates a Nomex, NFPA-1975-compliant station uniform worn underneath Nomex wildland PPE is appropriate for WUI firefighting. With the “more is better” philosophy, attention is wrongly paid to how the fire burned the firefighter rather than how the firefighter got burned.

On WUI fires, a balance must be continually struck between protecting firefighters from external heat loads (the fire) and protecting them from internal heat loads (the metabolic heat generated by the body, which must dissipate through evaporative cooling). The migration of municipal firefighting agencies to a thicker PPE uniform has made it more difficult for firefighters to properly manage their internal heat loads, especially when those firefighters transition from a structure protection role to extensive perimeter-control operations.

Does your double-layer PPE policy cover burn prevention in lieu of adequate preparation through fitness, nutrition, hydration and baseline training? Or does it allow firefighters to make adjustments to their PPE in the field when their internal heat load is a greater risk to them than the external environment? Are they prepared to mitigate the risk for external burn injury without that extra layer?

Investigative Findings

Several investigation reports of incidents that occurred in Southern California and involved firefighter fatalities—including the Glenn Allen, Calabasas, Camuesa, Cedar and Esperanza fires—have found that WUI firefighter training and work practices are inconsistent with and irresponsive to recent changes in law, findings of after-action reports and currently available research. In other words, we keep making the same or similar errors in judgment in similar situations.

Independently, each investigation report calls for specific changes in the industry. Taken together, the researched material calls for an overhaul among structural departments that fight WUI fires. Regarding PPE, this means that during WUI firefighting operations, firefighters should have options given to them through improved preparation, training and flexible policy. The multi-mission firefighter must have the knowledge, experience and tools to act accordingly, adapt to any situation, recognize and apply conditional rules and work practices in a dynamic situation and always maintaining a high level of safety.

The Mannequin Doesn’t Lie
So I’ll ask the question again: Why are firefighters wearing double-layer PPE? According to OSHA, all protective clothing, no matter how many layers, must meet flame-resistance requirements. NFPA 1977 is more specific, stating, “The goal of this standard was to provide thermal protection for the wildland firefighter against external heat sources with flame-resistant clothing and equipment while not inducing an extraordinary internal heat stress load.” Both the OSHA and the NFPA standards mandate a single layer of clothing as a minimum. Note: The NFPA 1977 standard does recognize that two layers provide better thermal protection, approximately 30 percent, according to available tests.

Unfortunately, the impacts on firefighter physiology are largely untested. Have you ever watched a Nomex flame-resistant test? The engineers performing the test dress a mannequin in the given PPE, then gas jets are ignited, enveloping the garment and the mannequin for 2 seconds at temperatures reaching 1,800 degrees F. When finished, the engineers discuss how well the garment performed underneath the heat and flame load. That’s great, but what about the mannequin? The poor thing never survives the test! The point: PPE can most likely survive under high temperatures with little or no damage; the human body cannot.

Look at it another way: Think of Nomex PPE as ANSI safety glasses—they’ll protect your eyes from a small projectile or splash of liquid, but not from a large rock or other inundation. Do you usually think of your Nomex PPE as simple safety glasses? Or do you push the limit of your PPE, getting closer to the fire than you really should or need to? Perhaps all testing for firefighter safety gear should be performed with real people. If actual living firefighters were used, we’d be very hesitant to don safety glasses and fire a big rock at them. If we performed that test, and the glasses survived, but the firefighter’s head was crushed, would that be OK? Studies show that double-layer Nomex is 30 percent more heat-resistant than single-layer. If you’re the mannequin, would you think two layers of Nomex are any better than one? Is 30 percent buying you anything? The bottom line: If a firefighter is close enough to a WUI or wildland fire to suffer a severe thermal burn, they’re too close—PPE won’t save them.

Improvements Made

Over the past few years, some fire agencies have made changes, which are listed below, to their work practices to improve wildland firefighter safety and fireline heat stress mitigation. Important: If your department engages in WUI firefighting operations, and wears double-layer PPE as described, I strongly urge you to consider the following points as additional safety measures, because of the added demands on firefighters’ bodies.

These measures just might save your life and the lives of your brothers and sisters.

•Provide integral line gear that supports efficient hydration, fire shelter deployment and personal gear storage. Studies have shown that a firefighter will drink 50 percent more fluid if it’s immediately available at the mouth (bladder and tube system) vs. at the belt (canteen style).
•Make PPE policy changes that support adaptation to the multiple missions found on WUI fires. Firefighters must be prepared to transition from perimeter control to structure protection to structural firefighting and back again. Get into the weeds here—how will your personnel equip themselves in each situation? How and when or will they change PPE in the field?
•Encourage fire season physical fitness that supports WUI perimeter-control operations. Emphasize exercises, such as hiking or running over variable terrain and full-body exercises that use arms and legs at the same time.
•Enhance seasonal WUI/wildland refresher training to include heat stress management. Unscheduled breaks by fireline personnel are a key indicator that something is wrong. Evaluate your personnel in the field for heat injury when you see them taking an unscheduled stop and appear to be overly fatigued
•Add basic NWCG 310-1 (Wildland Fire Qualification System Guide) coursework to your wildland training curriculum. This is a challenge for municipal departments that occasionally fight WUI fires because the classes are typically delivered in a 40-hour format. Better support is needed to deliver this training to the majority of municipal firefighters. In the meantime, add what you can where you can. Each course builds on an invaluable skill set.
•Incorporate a fireline ALS capability, especially for protracted, distant operations. Firefighters love to work, live in denial about their own suffering and are late to recognize symptoms of heat injury. Having ALS available in remote locations will enable prompt treatment if injury occurs.
•Schedule rest periods into WUI and/or wildland incident management. (California state law now requires employers to give rest periods to their employees to prevent heat illness.) As an incident commander, it’s necessary to ensure that personnel have routine rest. But don’t leave it up to your personnel; clearly communicate your expectations for rest time.
•Incorporate planned heat stress mitigations for hot days. Will your personnel have that cup of coffee or other “energy drink” when it’s above 105 degrees F outside? Should they continue to do physical fitness training on a hot day? What about routine training? Should that continue? Studies demonstrate that firefighters report to work each day voluntarily dehydrated. When it’s really hot out, take actions to limit physical activity, break the morning routine and add mandatory rest so your firefighters are prepared to operate in the heat safely.

The cause of fireline heat injury isn’t just thicker PPE. However, one purpose of this article was to prove how little Nomex PPE actually does for you. The other purpose was to outline available options for successfully managing safety in a multi-mission WUI environment. Fire managers and firefighters alike should know what their PPE is for. They should understand its limitations. Don’t enforce a PPE policy just because “everyone else is doing it.” Prioritize your risks, prepare your firefighters and give them the latitude they need to make the right decision at the right time.

Nomex WUI PPE offers the same type of protection as your $5 safety glasses, so don’t push its limitations. If you do, you’re basically putting on those safety glasses and facing a really big rock coming at you.

Vaughan Miller has served 24 years with the Ventura County (Calif.) Fire Department. He has promoted through the ranks, specializing in urban search and rescue, as well as WUI firefighting. Currently an assistant fire chief, he also holds a Bachelor of Science degree in Architecture from California Polytechnic State University, San Luis Obispo. Miller also chairs a working group focused on heat injury prevention made up of WUI firefighting agencies in Southern California.

This article originally ran in the July 2008 issue of FireRescue magazine.

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Comment by Patrick Brown on July 20, 2009 at 12:25pm
PPE is not just a wildland firefirefighter problem. This is a problem that is affecting the industry as a whole. Stress related injuris account for 50% of all firefighter fatalities annually. Studies have shown that the PPE increases core body temps, increases heart rate, decreases stroke volume which decreases blood pressure and increases sweating which leads to dehydration. All of these stressors lead to strokes and heart attacks. In addition, PPE has proven to be more difficult to work in. Tasks like walking, climbing, advancing hose, raising ladders and chopping are more difficult in bunker gear plus it impacts our balance and gait negatively...these issues compound the other issues which further increases the stressors. A safe median needs to be developed. The industry as a whole needs gear that provides us a relative level of safety without over stressing our bodies. We need lighter more ergonomic gear. More is not better.
Comment by Mike Schlags (Captain Busy) Retd on July 16, 2009 at 4:40am
Santa Barbara City Fire Department lost one of it's rookie firefighters on a wildland fire. The cause of death was not from direct contact with fire but in fact there was no active fire involved at all. The firefighter had the full PPE and died of heat stress, with water in his canteens... he died in the black.

We have learned from this tragedy and have changed how we fight wildland fires. We have adopted the USFS policy for nomex cargo pants, short sleeve tee shirts and a long sleeve nomex shirt. The work is arduous enough without piling on more protective clothing. Training is key here as your article pointed out. Common sense should tell you that less is really more. Thank you for a well written and thoroughly researched post.


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