Beans & LegumesWhat is an MRE heater and how does it work?
An MRE heater is a little bag designed specifically for heating MRE entrees. They are self-contained, and all you need is water (or any liquid for that matter)! It is an aluminum-lined polyethylene bag with a magnesium-combination filler at the bottom of the pouch. I’ve personally used these bags a many times and they are wonderful (and HOT!)! These heaters are perfect for heating entrees, and with how hot they get I’d say you might even be able to stretch it for 2 entrees or your side dish!
Now, how does the actual heater itself work? At the bottom of the MRE heater pouch is smaller sealed pouch that contains magnesium. The chemical reaction with the magnesium and the water starts to work immediately after you add the water. When metal rusts, the oxidation process generates heat. Usually this takes such a long time (years), the heat is not noticed. However, in this heater there is Magnesium dust(which burns, or rusts, much faster), iron dust, and salt. This combination of minerals creates a rapid reaction and generates a lot of heat when water is added. Think of it as an Magnesium and Iron bar in water rusting in just a matter of seconds rather than years!
Here’s how you get your Meal Ready to Eat nice and hot! You start by cutting off the top of the bag (there is a tear notch if you don’t have scissors). Next, you pour the water in the bag, making sure not to pass the fill line (it takes about 1 ounce of water). Then take the MRE out of the cardboard box and slide it in the MRE heater pouch. Fold the pouch so the open flap is on top and the heater is on the side of the entree. Slide the whole MRE pouch with the meal back inside the cardboard box, and let sit for the designated time, usually about 10 minutes, and enjoy a delicious and hot meal. It’s that easy!
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When I was in the Army we used to heat them up on the block of the old jeep motor (pre-hummer). This sounds alot easier!
March 18th, 2009 at 11:02 pmI have never tried heating up the MRE on an engine, but I have heard of that from many people. The great part about the MRE heaters is you can always have a hot meal regardless of wherever you are. Thanks for your comment.
March 19th, 2009 at 8:52 am[...] to know the different ways people have heated up there entree’s. In our blog post “What is an MRE heater and how does it work?“, we had a comment from Vince. He wrote “When I was in the Army we used to heat them [...]
March 12th, 2010 at 8:35 amI would change the order of a few steps. After tearing the pouch open, then you should remove the MRE from the box and insert it in the heater pouch. THEN, add the water, fold pouch, re-insert into box.
I make this suggestion because, as you stated, the chemical reaction is fast, i.e. the production of heat is fast. I can’t count how many MRE’s I’ve eaten in a lifetime, but I can tell you that you don’t want to fuss with sliding the meal into the heater while it is producing said heat!
August 31st, 2010 at 8:32 amI think you are mistaken about the content of mre heaters. First off magnesium doesnt rust it oxidizes. I believe that the heaters contain a mix of calcium carbide and iron.The steam emitted from an mre heater contains acetyline gas. Calcium carbide conbined with water produces acetyline, magnesium combined doesnt. When burning magnesium comes in contact with water it separates the hydrogen and oxygen and burns them both as fuel, thats why you get a violent reaction from putting water on (Burning ) magnesium. Unlight magnesum ; even in powered form will not react with water at all. You just get a grayish pile of mush.
November 21st, 2010 at 2:04 amMr. Walker has it right. It’s Calcium Carbonate, though. The “ate” gives it more electrons, making it less stable and more apt to reaction with the water. And, yes, Acytaline gas is produced, which is highly combustable (heck, it’ll self combust at over 15psi!) and no fun to get in your eyes while trying to jiggle an entre into the bag. Hmmm. Are you one of those “couch commandos”? Because I found a lot of sophestry in your article, but no real facts. Boy you SOUND like you know what your talking about, though. Giggle.
November 30th, 2010 at 5:05 pmThe latest in LA
January 17th, 2011 at 1:59 pmI don’t necessarily think Mr. Walker is right. While the reaction he explains reaction would create Acetylene, Calcium carbide has the dangers of containing toxic impurities. Especially since the production of calcium carbide requires a lot of heat, thus would be costly to pay for just the heater. Where did you get the info that Acetylene is created inside MRE bags? I believe it may most likely be a combination of citric acid monohydrate C6H8O7 . H2O and Calcium oxide CaO, creating an exothermic reaction when reacting with the water and then the acid works as a secondary neutralizing reaction to limit the amount of heat produced by the initial CaO reaction. It limits the heat of the reaction to the boiling point of water, which is about as hot as an MRE bag gets.
Sources:
U.S. Patent Office. United States Patent #3,550,578
EPA site on CaC manufacturing
http://www.epa.gov/ttn/chief/ap42/ch11/final/c11s04.pdf
February 22nd, 2011 at 4:46 pmI have a magnesium strip normal tap water sea salt and iron rust and mix in a glass pot but there are no reaction or heat in this mixture only a few bubble very slowly at a long interval how i can to convert this process to MRE heater tell me
January 17th, 2012 at 2:52 pmIt is commonly know among soldiers that mre’s have been used to build small ieds … Ranjeet, don’t blow off your fingers
January 25th, 2012 at 3:51 pm