"Your Fire Shelter" Pamphlet (Review Annually!!)
(Campaign to remind firefighters about proper use
of the fire shelter.)
The following is a report on the preliminary findings of
direct flame contact to fire shelters.
(These findings were distributed to DOI employees on 9/10/99)
Fire Shelter Technical Alert
Fire shelter training has for years stressed the importance of deploying fire shelters where there is no direct flame contact. However, the results of recent tests by MTDC have shown us that avoiding flame contact is far more important than was ever realized. New technology in video recording equipment has allowed us to see how flame contact causes the fire shelter to break down. When flame or any convective heat touches the shelter, the glue used in the shelter material produces gas, filling the shelter with smoke. This smoke is flammable. When a flame enters the shelter, through a pinhole or under the edge, the gasses can ignite causing a flashover. After the flashover the shelter material continues to burn. This fire is inside the fire shelter. Damage ranges from small holes in the aluminum outer layer to large holes in the aluminum and fiberglass cloth to total destruction of the shelter, depending on the amount of convective heat involved. We have seen this damage caused by grass and ground litter fires as well as by intense flame fronts. For example, a shelter placed well away from an intense flame front was burned by light ground fuels that were left after the area was cleared by a dozer.
The limiting factor on the shelter's durability appears to be off-gassing and ignition of the adhesive. We do not yet know the exact temperature or heat flux that causes this, but have found that is much lower than previously thought. The ignition inside the shelter causes rapid delamination and flaking of the aluminum foil. It has been found that once the heat load outside the shelter is removed, the shelter material stops burning in a matter of seconds. If the intense external heat load continues, offgassing and combustion also continue.
Firefighters have survived entrapments in shelters with areas of delamination and missing foil. They may have experienced fire within their shelters. We still believe that the conditions inside the shelter will be better than those outside the shelter, but that flame contact radically reduces the protection offered by the shelter.
We have always known fire shelters have their limitations. In light of these new findings, it is highly important that firefighters recognize the importance of deploying shelters in as large and fuel-free area as possible. Gravel or paved roads, areas cleared by dozers to mineral soil or black areas with no residual fuel are suggested as deployment sites. Remember that small brush, ground litter, grass or firefighting equipment have the potential to burn the shelter. These precautions are in addition to those suggested in the pamphlet, "Your Fire Shelter, 1995 Edition," particularly those related to situations that would expose the shelter to flames or convective heat (chimneys, steep slopes, draws, etc.).
First and foremost, remember that all firefighting tactics must be selected to ensure firefighter safety at all times. Escape routes and safety zones must be known by all and must be continually reevaluated. It is important also to recognize that the fire shelter has limitations. It is not a guarantee of your safety. It is a last resort. However, if you must deploy a fire shelter, it is extremely important that you deploy in an area where flames will not contact the shelter.