Disposable Heat Packs and Staying Warm
Author: Derrek Sigler
That magical time of year is here again and you’re all set for opening day of deer season. But Jack Frost has been working overtime and has whipped up a brutally cold November morning. Do you stay inside? Of course not, but how do you keep warm? Disposable heat packs can make a miserable day quite tolerable, even dare I say, comfortable?
What are they?
Disposable heat packs come in many shapes and sizes directed at a specific application. They create heat for a given amount of time and then you dispose of them. They are inexpensive and to most are worth every penny.
How do they work?
Most disposable warmers work via a chemical reaction with air. Just as with a fire, they have to have air to operate. The ingredients to the reaction are iron, water, cellulose, vermiculite, activated carbon and salt. When the iron in the pouch is exposed to oxygen, it oxidizes. When iron oxidizes, it produces iron oxide, commonly referred to as rust. The reaction creates heat. The salt in the pouch acts as a catalyst for the reaction. Think of a piece of bare metal that gets exposed to saltwater. Carbon, also in the pouch helps disperse the heat, and the vermiculite is used as an insulator for the purpose of retaining the heat. The cellulose is added as filler. With most disposable heat packs, a polypropylene bag that allows air to permeate the ingredients while holding in moisture surrounds all of the ingredients.
If you’ve ever used one of these heat packs before and had a bad experience, you may want to look at how you used it. The number one mistake when using these packs is not giving them time to complete the reaction. All too often, one will take the packs out of the packaging, give them a shake, and then toss them into boots or pockets. It is far better to shake them up a little and then leave them on your dash or table until you’re ready to go into the field.
If you’re using them and want to stop for a while, but don’t want to waste the pack, a technique you can try is cutting off that supply of oxygen. Let’s say you’re hunting and have a warmer that is good for twelve hours. You’ve hunted the morning and want to go out again in the evening, but don’t want to use another warmer. A zip locking-type bag, such as you’d use for a sandwich can be used to slow down the reaction. Simply toss in the heater and squeeze as much air out of the bag as possible. Without air, the reaction slows. Open the bag before you want to go back out and give the heater time to warm back up, and you should be good to go. If you have one, a vacuum sealer will do an excellent job of this, but isn’t the cheapest route due to bag material cost. While the heaters are not reusable, slowing down the reaction will extend the life of the heater, saving you money.
It is important to note that you also need to keep them dry. Just like tossing a bucket of water on a campfire, getting one of these heater packs wet will extinguish the reaction. Staying dry is such an important part of staying warm anyway. Your boots need to be waterproof if you’re using toe warmers in wet conditions. Your gloves need to be as well if you’re using them near water or in wet conditions such as duck hunting. You’ll also want to have breathable layers to keep sweat from extinguishing them as well. A hike into a deer stand might make you sweat a bit, which can bring down your temperature when you get to your blind and sit there all day.
How do you use them?
Toe packs are designed to go into the toe of a boot and keep those tootsies nice and toasty. They should always go between your socks and the liner of your boots, and be sure to let them get fully warmed up before tossing them in your boots. If you’re boots are tight, try going to a thinner sock as they still need air to work.
Hand warmers can go in your gloves but direct contact with skin is not advised. Try using them in your pockets or with a pair of liner gloves. One of my favorite uses is tossing them into a fleece muff hand warmer. The heat from the pack will make the muff very warm, and much of the time allows me to wear a thinner glove for added mobility when I need it. Grommits are another option worth looking at. They offer plenty of room for a liner gloves and a heat pack without being too binding.
The larger body-warmer packs are very versatile. For placement, think about where your blood is flowing. All the blood in your body flows through your kidneys so placing heat packs accordingly can go a long ways toward keeping your core temperature where you want it. If you want to keep your legs warmer, place a pack near your lower back. Your femoral arteries branch off near your tailbone so placing heat there will allow your blood to carry that heat down into your legs. The same can be said for placement of a pack between your shoulder blades to keep arms warmer. The neck is a near ideal location as it receives blood from the heart first. My personal favorite location for warmer packs is my head. You have quite a bit of blood flowing through your scalp. I will warm up a pack and toss it into a fleece hat on a cold day. The fleece breathes enough to let air in and keeps enough of the heat to keep me quite warm.
Another great use for the larger heat packs is warming up the sleeping bag when you’re out camping. Remember the old stories of heating a rock in the campfire then putting it at the foot of your sleeping bag? I’d sure hate to accidentally put my foot on it! A heater pack will do the same thing, but be much safer. Your feet will thank you, and you won’t end up with soot from the fire getting all over everything.
I went off to college in Michigan’s Upper Peninsula, a place known for big deer and bitter winters. I was going to a small state university in Sault Ste. Marie, at the eastern end of Lake Superior. Winter came early that first year and with it record bitter temperatures. It was not uncommon to see temps drop below the negative twenty-degree Fahrenheit mark.
Now being a college kid and always looking for fun, I started playing hockey with some friends in the evenings. We’d go to an outdoor rink to play when it was so cold, water in a bottle would freeze before you could drink it. This was a perfect environment for disposable heater packs and thankfully, I had a good supply.
I would use toe warmers with heavy socks, and hand warmers in my hockey gloves between a liner glove and the actual glove. I would also wear a fleece hat with a pack underneath, and a fleece neck warmer with one. I’d throw on a turtleneck shirt so there was material between my skin and the warmer. I’d then have one on my lower back. This set-up with a good set of thermal underwear, and a couple layers of not-too-heavy-clothing kept me warm with modest physical activity (I usually played goalie). I’ve used the same basic set-up for hunting, fishing, and other cold weather activities ever since.
At the Core of the Issue
Keeping warm is a matter of keeping your core body temperature at a reasonable level. Once that core temp drops, getting it back where you need it to be can take a great deal of energy. A lowered core temp combined with loss of energy can spell disaster in the wild, or even your backyard. Disposable heat packs offer an inexpensive solution to staying warm.
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