Our field experience with these things basically rates them as ‘the cat’s ass’ when it comes to giving us an edge in inclement or cold weather in the task of staying functional by being warm or recovering from hypothermic symptoms.
Our NPT members always carries a minimum of 3 pairs of hand warmers in our rucks in ‘warm’ weather, and 6 during fall, winter, and spring (this year, that’ll mean till about late May, the way things are going…) and a like number of toe warmers for some very good reasons:
- They are great when working in very cold weather without gloves for detailed tasks. Holding on to them for 30 seconds to a minute brings your hands back to full dexterity, and then when placed back in your pockets, help warm your torso.
- They are phenomenal when setting up a shelter at night to throw into your sleeping bag while you’re doing other tasks because they help warm the batting (we also have been known to use toe warmers on our sleeping socks if it’s really cold). Then, while sleeping, keeping one near your torso and one near your feet helps, especially if you don’t have an arctic rated bag and you’re in the north country, like we are, where it’s routine for temps to drop well below zero and winds to reach 35mph sustained with even higher gusts.
- They are a great first aid item for dealing with hypothermia that is safe and won’t cause burns. We place one under each armpit and one in the crotch of the victim will help core temperature come up more quickly when used in conjunction with other core temp raising methods. Optionally, we might take the 4th (as they are in pairs) and place on the chest, depending on the situation and the condition of the person.
- They are extremely light, and provide a superb ROI (Return On Investment) when balanced against weight, bulk, and cost.
We carry them year round because hypothermia can happen in a great majority of environments (having lived in states like Texas, Idaho, Nebraska, Upstate New York, Michigan and other regions, I can vouch for how cold can get in so-called ‘warm’ regions at night) and conditions, and it’s better to have them and not use/need them, than the reverse. In a GOOD situation, or during a sustained rain when you’re outside of a warm, dry location, they can make a world of difference in personal warmth and comfort without having the tell tale signs a fire will provide, such as wood smoke and light. When someone is warm, the body recuperates more quickly from exertion than when cold, and much energy is used to keep core temperatures up. We also try to get the longest lasting models available. Bang for the buck and all that.
As they’re air activated and come in air ‘resistant’ packaging, we extend their shelf life by vacuum sealing them. Doing so puts another impermeable layer of protection around the unopened package. YMMV.
The toe warmers do have a drawback if you wear them while walking a good distance. They will harden as foot perspiration penetrates them, causing the wearer mild discomfort after a time.
http://www.warmers.com provides the information on how they work:
Warmers operate on a chemical reaction with air similar to rusting. The warmer ingredients are iron, water, cellulose, vermiculite, activated carbon and salt. The heating process takes place in this fashion:
- The iron in the pouch, when exposed to oxygen, oxidizes and therefore produces heat (aka, “Air Activated”).
- When iron oxidizes it produces iron oxide, more commonly referred to as rust.
- The salt acts as a catalyst.
- The carbon helps disperse the heat.
- The vermiculite is used as an insulator for the purpose of retaining the heat and the cellulose is added as a filler.
- All of these ingredients are surrounded by a polypropylene bag.
- Polypropylene allows air to permeate the ingredients while holding in moisture.
They are non-toxic, so no worries there, but they’re not edible. Pets and small children will eat anything, so a word to the wise.
When it comes to discarding them in the field, we do the same thing we do with food wrappings: stuff them in your ruck and take them with you. Don’t leave a trail for others to follow, as they may not mean you ‘good things’, just sayin’.