What safety equipment do you guys carry with you when you’re out in the nature? Whistle, orange survival bag, foil blanket, head torch, first aid…….check! How many of you carry a group shelter or “bothy bag”? Running courses in the Highlands of Scotland, we would put a conservative number of our clients turning up with one at 50%.
“But I always carry an orange survival bag with me, this does the same thing right?” Yes and No, we’ll come back to that argument in a second!
Cast your minds back to School (daunting I know), now remind yourself of the 4 main ways the body loses heat…..here’s a quick reminder;
Radiation – We are constantly radiating body heat to the external environment, the 2nd rule of thermodynamics states that “heat passes from a warm source to cold, to try and reach an equilibrium”. This is why we wear clothes right? The clothing basically stops the heat dissipating from our body quickly, and traps warm air against our skin.
Conduction – Same as above, if you lie, lean or make contact with a colder surface than your body temperature, you will lose heat to that cold source. Hence why we use sleeping mats/thermorests.
Evaporation – As we all know sweating is natures way of losing heat as quickly as possible when we are trying to achieve “Homeostasis”, the act of balancing our body temperature with the outside climate. This is paramount in hot climates or when exercising. However evaporation can be one of your biggest enemies when you are soaked with rain or sweat and are stationary. Your body warms the water particles against your skin, turning the water into vapour, and carrying heat and energy at quicker rate than air away from you.
Convection – In an outdoor setting convection is “wind chill”.We’ve all been there, hanging out your hoop, overheating going up a steep hill, then you get to the top you rest for 5 minutes all the while getting hit by the wind, you wish you were on the move again! The wind moves heat away from the body at a faster rate. (This shows the importance of the layering systems in clothing) Below is a wind/temp conversion chart.
This goes to show you that it can be 10 degrees, but with a 30mph wind, it’ll feel like -1!
The Gruesome Twosome
In the majority of hypothermia cases in the outdoors it’s very rarely just the one heat loss mechanisms that does the harm, usually a mix of two or more. The real problem is when individuals get wet, either through sweat or rain/snow (Evaporation) and there is a significant wind chill (Convection). Evaporation+Convection = Big trouble! This is when the “rule of three’s” comes into force, without adequate protection from the elements you’re going to last a maximum of 3 hours before the symptoms of Hypothermia are so bad…..it’s probably too late.
Group Shelters and the Fjallraven Windsack 3
Like most things in life it’s the simple things that can make all the difference. The fjallraven Windsack 3 and other Group shelters are basically a tent material that can fit individuals, or a number of you in and keep you sheltered from the elements. Group shelters aren’t just a survival piece of kit, but can also be used to have your lunch in, if you can’t get out of the wind.
So looking back at the 4 mechanisms of heat loss the Wind sack 3 and group shelters will stop;
Radiation – Fjallraven use the same materials as the outer on their tents (40D TripleRip nylon) , this means that any radiated heat is trapped in the bag itself and is allowed to freely circulate. This is even more evident when there are two or more of you in there, the temperature will noticeably rise quickly
Conduction – When using a group shelter, ruck sacks should be placed on the ground and sat-on to stop conduction to the ground.
Evaporation – Ok, so a group shelter won’t stop the act of evaporation, however the heated vapour will be trapped in the bag itself to avoid excess heat loss. The great thing about the wind sack 3 is the three individual zippers, which allow airing and stop excess condensation on the inside.
Convection – You’re still going to feel the wind if it’s strong enough in a group shelter, but it’s not going to be able to draw the heat away from you at the same rate.
As was stated above “an orange survival bag does the same thing”, yes it does, but can only really be used once and is a “one person shelter”. Don’t ditch the orange survival bag, just make sure you carry a group shelter with you from now on.
It’s worth noting that the orange survival bag should be pulled over the head, with an “air hole” made for breathing/avoiding condensation (pictured). This will assure radiated heat is trapped in the bag with you.
Most group shelters will come in bright colours, this is obviously so rescuers can spot you, should you need to deploy it “in anger”, the Wind Sack 3 comes in UN blue. The two colours that are unnatural and are picked up easiest by the human eye are Orange and UN blue, so when buying a group shelter bear this in mind.
Two other great features of the Wind sack 3 that we’ve noticed are the reflective tape around the outside….easily picked up at night, but also the carabineer on cordage (pictured) that you can attach to you in high winds (those of you who use a group shelter regularly will know all about the potential for the wind to rip it straight out your hands!)
Let’s be honest here, many of you will be on a budget and might not be able to afford the Wind sack 3 , however a trip to any reasonably reputable outdoor shop and you’ll be faced with a wide range and at a reasonably cheap price.