Emergency space blankets must be used correctly

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What should I know about emergency space blankets?

We were snowshoeing the other day with folks who did not seem to be prepared for an adventure even a couple of miles back into the snowbound wilderness. They used a small "fanny pack". I asked them what they would do to protect themselves during an emergency stop for an injured or lost companion, or if the weather closed down to hard wind driven snow with trails and ways disappeared. All of them said they had a "space blanket" to keep them warm.

There-in lies the danger!

I have heard this claim before, that "a space blanket can be used for warmth". I have always said the term space blanket is a misnomer, the thin plastic sheet is neither a miracle material nor a blanket.

It is well known that heat is lost from the body in 5 ways: Convection, Conduction, Radiation, Evaporation and Respiration. Excessive heat loss causes hypothermia.

"Blankets" trap air for insulation, the thicker the blanket the higher the insulation rating. Blankets do not add heat (unless the blanket is warmed in a hospital situation).

A thin plastic sheet has no insulating qualities, indeed, the plastic immediately becomes as cold as the snow or the wind blown air and will immediately conduct that cold through wet clothing to the body. A space blanket is not a blanket! If you lie down on a plastic space blanket placed on the snow the cold will immediately be conducted to your compressed clothing. You must carry extra insulating clothing layers and an insulating ensolite pad! Read the Essentials.

How heat is lost by the climber

"Convection
When wind blows against the skin, it helps speed up the processes of evaporation, making the person feel much colder (often known as the wind chill factor). The 'Life' Blanket forms an impermeable layer between the skin and the wind, helping to prevent heat loss through convection.

Conduction
Heat may be lost through contact with surfaces at a lower temperature than that of the body. Although the 'Life' Blanket's insulating properties help prevent this (particularly the thicker reusable blanket), the patient should always be placed on an insulated surface, if possible.

The blanket should not be wrapped too tightly, as the air trapped between the blanket and skin provides further insulation, helping to prevent conduction of heat to the outside environment.

Radiation
Heat is lost through radiation from all over the body. The 'Life' Blanket will reflect back over 90% of this radiated body heat, warming the patient in a natural and progressive fashion. It should be noted here that the hands, feet and as much of the head as possible should be covered by the blanket.

Evaporation
Heat is lost through the body's natural cooling system (perspiration) which evaporates from the skin. The Blanket, if used properly forms a closed tube around the patient. This increases the humidity of the air next to the skin, and slows down the evaporation process.

Respiration
The only other way in which heat is lost is through respiration (breathing), and this should be attended to with an inhalation re-warming unit where one is available, or by covering the mouth and nose area with wool or a handkerchief.

This is what the English manufacturer of the Kelvalite 'Life Emergency Blanket' suggests:

(Note: An emergency sheet of thin Mylar or Kelvalite plastic (an "Emergency Blanket"), properly used, minimally can help reduce heat loss a bit in four out of five heat loss categories. Carry one with your Personal Medical Kit). --Webmeister Speik

IMPORTANT
"It should be stressed here that the 'Life' Emergency Blanket should be used in conjunction with any other hypothermia/core warming treatments if available - however, in an emergency situation the 'Life' Blanket is far more efficient than traditional cloth or synthetic blankets.

Using the 'Life' Emergency Blanket couldn't be easier - just unfold and wrap around the patient.

To be at its most effective however, the points below should be observed:

Unfold the blanket completely and lay flat on the ground, preferably on as warm, dry and insulated a surface as possible.

Lay the patient on the blanket, leaving about 12 inches of blanket overlapping at the 'feet' end. The blanket is most effective when used directly next to the skin - if required material blankets may be wrapped on the outside of the Emergency Blanket.

Fold the end of the blanket over the feet, and bring the two sides up and over to overlap at the top.

If possible secure the blanket with some tape - the better the seal the more efficient the blanket will be.

Do not wrap too tightly as the air which is trapped contributes to the insulation - see Technical Information section for further details.

Be sure that the feet, hands and as much of the head as possible are covered. If necessary use another blanket (or a child size one) to wrap around the top of the head, leaving the nose and mouth uncovered.

Use an inhalation re-warming unit if available, or cover the mouth and nose with wool or a handkerchief to help slow down heat loss through respiration.

The patient may complain of feeling clammy or uncomfortable - this is perfectly normal and simply means that the blanket is working. The closed 'tube' means that moisture cannot escape - this causes the humidity levels next to the skin to increase, and slows down the patient's natural cooling system (evaporation via perspiration)."

Harrison Insulating Systems
The English manufacturer of the Kelvalite 'Life Emergency Blanket'

The "Emergency Bivy Sack" is the gear that we suggest:

My friends and I each carry an Essential insulating 12 x 12 inch "butt pad" in our daypacks year around and in winter we also carry a larger 24 x 48 inch Essential insulating pad such as the Cascades Designs Ridge Rest Short (only 6oz.) secured to the outside of the winter pack to insulate us from the snow. Our winter day packs are large enough to carry extra hats and gloves and enough extra insulating clothing such as puffy down or pile jackets (and sometimes down pants) and our light Gore-Tex jacket and pants to keep us protected from wind and wet.

A plastic space blanket should not be a substitute for your outer layer of Gore-Tex clothing or the Emergency Bivy Sack described below. (A plastic space blanket (2oz.) can be carried in the Group First Aid Kit to provide a clean area on which to tend an injured companion.)

My friends and I each carry a 9oz. "Emergency Bivvy Sack" sold by Adventure Medical Kits for about $30. This is a "bivy bag" made from a "tough, four-ply, waterproof, windproof fabric (Thermo-Lite®) sandwich", which is designed to keep the cold outside layer from conducting to the inside layer. It is designed to prevent Convection, Conduction, Radiation, and Evaporation. We will breath through our wool scarves and calm our breathing to limit heat loss from Respiration. These Thermo-Lite® Emergency Bivvy Sacks are sold at REI and Mountain Supply in Bend Oregon.

(This is about the size of a fat quart Nalgene bottle)