In 1990 on the Wenatchee Heights Fire in central Washington, the local fire chief attempted to ride out a burnover in the cab of an engine. Rick West thought he knew the fuel conditions, but he was unaware of the woody component. That fuel resulted in a high-intensity, long-duration flame front that compromised his safety in the cab of the engine. When the heat became so intense that it blew out the engine's front windshield, he was forced to leave the engine and run through open flames, suffering third-degree burns over much of his body.

Five years later, two volunteer firefighters were burned to death on a fast-moving fire outside of Boise, Idaho: They were in a converted military 5-ton vehicle and had structural fire PPE but no fire shelter.

In recent years firefighters have been entrapped in their engines during a number of incidents. They have been forced to make instantaneous decisions about their best chances for survival: in an engine or in a fire shelter. As recently as 2003, two Idaho firefighters were killed when a wildland fire spread quickly and trapped them.

Such incidents were looked at by the U.S. Forest Service Technology & Development Center in Missoula, Mont., a decade ago when it was asked to conduct a study comparing conditions in a vehicle versus inside a fire shelter during a burnover event. While the specific focus of the study dealt with just measuring conditions inside the vehicles and shelters, the lingering question remains: What, if anything, can be done to increase the survivability of firefighters when they are trapped by a burnover in their vehicles, or when no fire shelters are available?

MEANS AND METHODS

It has been standard practice for federal firefighters to carry a fire shelter for more than 25 years, but many state, rural and volunteer departments couldn't afford to equip their firefighters with full wildland PPE, including the fire shelter. In case of an entrapment, their vehicle often became the only refuge available to them. In Australia and Europe, fire shelters are not used, so the fire vehicles again become the firefighters' last hope for survival in an entrapment or burnover.

The MTDC study was designed to quantify the conditions that existed inside the cab of an engine and inside a fire shelter — at the same time — during a wildfire burnover. The specific factors to be measured included air temperatures in the immediate vicinity of the engines and shelters and within engine cabs and shelters, radiant heat flux levels in the immediate vicinity of the engines and in fire shelters, surface temperatures on the outside and inside surfaces of the standard fire shelters and prototype stainless-steel fire shelters, and gas compounds released by heat and burning in the engines and fire shelters.

Vehicles were positioned in or adjacent to fuels as they would be configured normally in a typical wildland setting. For the grass-fuel type, they were placed in the middle of the fuels with no clearing; in the brush and timber fuel types, engines were placed on roads, immediately adjacent to the fuels but not in direct contact with them.

Fire shelters were erected in front of or behind an engine, using tent framing to keep them erect. Weights along the inside edge of the shelter simulated a firefighter holding the edges to keep them from rising during the burnover. These shelters were adjacent to the fuels, rather than in a preferable deployment site as far from the oncoming fire as possible. This ensured that the data gathered were fully comparable to that obtained from the engines.

Both the engines and fire shelters had gas collection devices placed inside to measure gases that could be harmful or fatal to an entrapped firefighter. The breakdown of materials inside the engine cab, such as petroleum-based plastics and sound-deadening materials inside the door panels, was a special concern, as was the off-gassing of the fire shelter adhesive that bonds the aluminum foil to the glass cloth.

Personal protective clothing, equipment and other items commonly used by wildland firefighters were laid out near the fire shelters to visually evaluate their protective value during an entrapment. Items included the standard Forest Service Nomex shirt and trousers; leather firefighter gloves; hardhat; military-issue flight suit; and various outer garments such as brush coats, FR coveralls from Canada and Australia, and shirts from various cooperators. Clothing was tested as though it were on a firefighter. Five-gallon water bladders were filled with water and covered with 100% cotton undershirts. The shirts and jackets were placed over the undershirt. The bladder filled out the garments and simulated a heat sink, not unlike that of the human body. While some of these items were not instrumented, we felt visual observation of damage would offer valuable lessons for firefighter training. Specialized fireproof video photography equipment was developed to take closeup shots of the fire's effects on the engines and shelters.

GOALS AND OBJECTIVES

This project's primary purpose was to gain quantifiable data on conditions in engine cabs and fire shelters under identical, real-life conditions. However, a number of observations are relevant to survivability in an entrapment.

In most fuel types besides grass and light brush, the temperature and radiant heat flux generally increase with the height above the ground. This is consistent with the principle that heat rises. This observation has special relevance considering the height of an engine cab compared to the height of a fire shelter.

Heat from the passage of the fire front appears to be retained in the vehicles longer than in the fire shelter or other items of PPE, indicating that the metal in an engine may act as a heat sink.

When fire comes up a steep sideslope, it appears to go over the top of an engine and under the chassis, creating an eddy on the back side that draws heat and flame. A firefighter taking shelter behind an engine parked on a steep slope would not be protected from heat or flame. This effect was demonstrated in October 1996 when an engine was burned over during the Calabasas Incident in Southern California.

Video footage shows that a large volume of smoke seeps into the engine cab even when the windows are tightly rolled up. This occurred under low-temperature conditions when the cab might appear to be survivable.

When the outside doors of an engine cab are subject to high radiant heat loads, the petroleum-based plastics and sound-deadening materials in the door dashboard volatilize. The smoke generated by this volatilization may cause both short- and long-term health effects on firefighters without respiratory protection, and will create conditions that force them from the cab into the fire area.

During moderate-intensity, short-duration exposure, exterior components of the engines either caught fire or experienced some melting. Under higher-intensity or longer-duration exposures, the engine could catch fire and continue burning when conditions outside would be harmful to a firefighter attempting to leave the engine.

For these tests, both the engines and fire shelters were placed in the area most likely to receive the highest exposure to the flaming front and the radiant heat flux. In a real-world fire entrapment, moving just a few feet back from the oncoming flaming front — especially on a road cut on steep slopes — appears to significantly reduce the effect of temperature and radiant heat flux on both the individual firefighter and an engine.

Because of safety concerns during testing, the gas tanks on all the engines were empty. In an actual fire operation, damage to the fuel tanks during a burnover could increase the danger to firefighters in or near an engine.

Observation of the exposed PPE indicated that under experienced radiant heat loads, the protective characteristics of the clothing and personal protective equipment appear to offer adequate levels of protection for an entrapped firefighter who has neither a shelter nor an engine for protection. Experience during the Calabasas entrapment showed that an engine became “oxygen starved” and quit running in a burnover situation. Firefighters hoping to escape a burnover by driving away in an engine should consider this possibility.

Under high heat loads, tempered glass in the cab's windows may break out. This may occur when the difference in temperature inside the cab and the temperature outside is only 4°C. Consideration should be given to using safety glass for greater levels of protection.

In a real fire entrapment or burnover, the human dimension is a critical factor. What is the experience and training of the individuals involved? Does their frame of reference allow them to recognize the situation they are in, and make the appropriate response?

How much time is available for the critical decision? Can you get all the exposed firefighters into an engine cab safely in less than the 20 to 25 seconds needed to deploy a fire shelter? Have firefighters considered the need for an adequate safety zone early on during the fire suppression, or do they consider their engine or fire shelter to be their “survival zone”?

GLOBAL LESSONS

Over the past three decades, recurring burnovers around the world have resulted in an ongoing effort on numerous fronts to improve the safety of firefighters in engines and tankers. Because the problem is common to so many regions, an improvement developed in one area may have a direct and immediate application half a world away.

In Australia, the majority of bushfire suppression activities are tanker-based, usually staffed by volunteer fire brigades in the various states. They have a long history of tanker burnovers that have resulted in numerous fatalities, and so in the late 1990s began an effort to study the dynamics of radiant heat from bushfires on their tankers.

An original study was jointly conducted by the Country Fire Authority in Victoria, and CSIRO, the Australian National research organization. This study was prompted by the survival of five firefighters on the Linton Fire in one Geelong City tanker, which had water left in its tank to supply its emergency sprinkler system; a second Geelong City tanker was out of water, and its five firefighters perished. The Aussie study was intended to look at sprinkler systems, protective curtains, and modifications to the interior of the tanker cab that would reduce the toxic off-gassing from plastics and other manmade materials.

About the same time that the two firefighters were killed in Idaho on the Point Fire and the five Aussie volunteers were killed on Linton, there was the beginning of activity around the world to develop protective systems and equipment for fire engines/tanker and other fire apparatus used on wildfires.

At a manufacturing plant outside of Seville, Spain, engineers from the Grupo Industrial Iturri have been working on a tanker protection system that creates a continuous flow of water over the outside of the tanker in an entrapment situation. They have plumbed tubing from the main water tank onto the external frame of the tanker body, with small holes along the tubing that allows the water to cascade out rather than coming out in a spray. They believe that this system is superior to a spray system, because the water particle size in a spray is more susceptible to evaporation from the fire's heat and being blown away by fire-related winds. The Iturri system is controlled from within the tanker's cab by the operator, eliminating the need for the operator to exit the cab area under burnover conditions. This system is widely used throughout the province of Andalucia and by other fire agencies throughout Spain.

The United States also has a long history of engines involved in burnover events in many geographically diverse parts of the country. In 1995 on New York's Long Island, five engines were destroyed on a single day in a fast-moving timber fire. Fortunately all the firefighters were able to escape and there were no injuries. Other engine entrapments and burnovers have occurred in California, Wyoming and Nevada.

In spite of those recurring events, little work has been done in the United States to develop specialized equipment for protecting firefighters trapped in engines. There's one company, however, that has developed products for use with both engines and firefighting dozers. Storm King Mountain Technologies was founded in 1995 by Jim Roth, whose brother Roger was one of the smokejumpers who died on the South Canyon Fire on Storm King Mountain in Colorado. An engineer by trade, Jim has been using his talents to develop a series of radiant heat — reflecting curtains that can be used both inside the cab and also for the crew compartment of engines. A modified version also can be fitted for fire dozers. These protective curtains are being used by some departments in Southern California and on tankers of the Country Fire Authority in Victoria, Australia.

Dick Mangan is the president of the International Association of Wildland Fire. He previously served as the fire and aviation program leader at the Missoula Technology and Development Center, where his major responsibilities include developing equipment for wildland firefighters, primarily personal protective equipment and equipment for smokejumpers. He serves on the National Wildfire Coordinating Group's fire equipment and safety and health working teams, and is chair of the National Fire Protection Association's technical committee for wildland fire personal protective equipment. Mangan has a bachelor's degree in forestry and more than 20 years of experience at ranger districts and national forests in Oregon and Washington.