Abstract
Introduction
Hypothermia is often cited as the second most common cause of wilderness mortality, and no studies were found comparing efficacy of hypothermia prevention systems or survival blankets.
Methods
Five 0.5-gal number 7 plastic containers were filled with 108°F water and wrapped in a single layer Army combat uniform (ACU) consisting of a polyester t-shirt under layer and polyester rip stop outer layer material around the entire container. The container and ACU wrap was placed in a mylar blanket, Heatsheets® bivy, Blizzard® bivy, Goretex bivy, or no insulator (control) and subjected to ambient temperature for 10 hours ranging from 46.5°F to 52. 0°F. The system was opened every hour, containers were agitated, and water temperature was taken with a Fisher Scientific thermometer.
Results
Mylar 10-hour heat loss was 46.2°F, a loss of 43.0%. Mylar costs $1.50, weighs 2 oz, and its durability was poor. Heatsheets® 10-hour heat loss was 48.1°F, a loss of 44.5%. Heatsheets® costs $4.99, weighs 3.5 oz, and its durability was fair; Blizzard® blanket 10-hour heat loss was 42.4°F, a loss of 39.2%. Blizzard® blanket costs $36.99, weighs 18.5 oz, and its durability was fair; Goretex 10-hour heat loss was 40.4°F, a loss of 37.4%. Goretex costs $85.50, and weighs 39 oz, and its durability was good.
Conclusion
All survival blankets performed better than the control with Goretex and Blizzard® blankets losing half as much heat as Mylar and Heatsheets® blankets. According to this study, Blizzard® blanket is a superior balance between size, cost, weight, durability, and efficacy.