Tuesday, January 3, 2012

Survival Blanket Review

   For those who spend a lot of time out in the rugged areas of the world, hypothermia is one of the constant threats that we face. As a Remote Medic it is important to have the best kit available to treat hypothermic casualties.

   This research was conducted for the Wilderness Medicine Society by Doctors Beeghly &  Caudell from the United States Army. Further information can be found at the WMS website. It is definitely worth the time to look through all of the research and medical information found at WMS. 
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.
   Four survival blankets were tested:
        1. Mylar blanket

        2. Heatsheets Bivy

        3. Blizzard Blanket

        4. Gortex Bivy

Methods. 5 half gallon plastic bins were filled with 42.2°C (108°F) water and wrapped in a single layer Army combat uniform consisting of a polyester t-shirt under layer and polyester rip stop outer layer material around the entire container. The container 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 8°C (46.5°F) to 11°C (52. 0°F) . The system was opened every hour, containers were agitated, and water temperature was taken with a Fisher Scientific thermometer.
Mylar 10-hour heat loss was 7.9°C (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 8.9°C (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 5.8°C (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 4.6°C (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.
     Best: Blizzard Blanket
     Good: Gortex Bivy
     Okay: Heatsheet
     Worst: Mylar Blanket
Andrew Beeghly, DO, FAWM, Capt. USA MC Michael Caudell, MD, FACEP, FAWM Augusta, GA, USA
Additional information can be found at RemoteMedicine.ie


  1. Some good information right there - I wonder how the figures would look if there was wind factored in? I reckon the Goretex bivvy would lose less than the blizzard bag as there's only one opening, as opposed to the velcro closure. That said, it could be quite difficult getting a non responsive patient into a bivvy bag in the first place!

    What was the heat loss in the un-insulated container?


  2. Hi Gavin,

    I agree with you. The Gortex Bivy bag would handle wind a lot better. In Special Forces we were issued these. I have slept in -40 and had myself a long comfortable sleep.
    I have also woken up with an inch of ice on the bivy bag and never felt it.

    On the downside, they are heavy and bulky compared to the blizzard blanket.

    The study didn't include wind chill factor.

  3. Do you know of any other published data or information addressing the efficay of mylar blankets?

  4. Hi,

    No, this is the only study that I am aware of.


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