Survival rates of trapped wildfire firefighters could be increased substantially by using new fire shelters – prototypes of which have already been developed by North Carolina State University researchers.
Researchers have found that four new designs for shelters could increase the survival time inside the shelters compared with the current industry standard. While conducting wildfire burn-overs simulations in labs, temperatures inside the shelters remained within survival limits for longer, and the shelters took longer to break open. Based on these findings, researchers are optimistic that their field tests will yield far better results and eventually new improved shelters. In addition, they hope the findings will inform new standards for shelter design and testing.
One problem with the industry standard shelter is that the aluminum outer layer will melt in contact with direct flame. Researchers worked on improving the overall design of fire shelters by incorporating an inner heat-blocking barrier and additional thermal insulation into the construction. With that goal in mind, the researchers designed two leading prototypes and two lighter versions weighing less than 5 pounds. They added insulating materials, and experimented with different seam designs to keep them from falling apart.
Researchers tested the designs against the industry standard in a test chamber called the PyroDome Turbulent Flame Fire Shelter Test System. They blasted the shelters with direct flame from propane burners for 60 seconds, and measured how long it took the temperature at the floor of the shelters to reach 302 degrees Fahrenheit, the temperature threshold for survival. They also set up cameras inside PyroDome to see when the inner layer of the shelters would break open.
All of the prototypes had improved survival metrics compared to the standard, which reached the survival limit in less than 40 seconds. Meanwhile, the temperature in one of their designs was nowhere near the survival limit temperature at 60 seconds.
The researchers also tested the shelters’ performance in variety of conditions in controlled burns in Canada, California, North Carolina and South Dakota. However, they found the field tests were not reliable enough to draw statistically significant conclusions because of wind, fuel and fire conditions.
The two tests in southern California had the best burn conditions, and researchers saw one of their prototypes performed well in a burn-over. In a test in South Dakota, researchers witnessed shelter failures when grass roots caught fire to spread under the walls inside the shelter. That underscored the importance of fully clearing the area around the shelter, and even scraping down underneath them to remove all organic material.
The new findings could give manufacturers and people developing these shelters a new target to shoot for in terms of both how to test them and minimal performance requirements.