I've just got my hands on a packet of Meals Ready to Eat (MRE) chemical heaters. I have just tried one - they are pathetic. Followed the instructions to the letter. I might as well stuck the meal pouch under my armpit. Do these things have a shelf life? They appear to be dated US1992 NATO STOCK 8970-01-321-9153. Whats the point of them. I've now also read that these things can spontaneously catch fire when they get damp and have possibly led to the deaths of US military personnel when they were stored at an ammunition dump. They are very messy to use also.

The following is a true story written by a friend of mine(it's kinda long) but it will answer your question kinda.
THE STORY OF THE ORIGINAL HOT PANTS
ONCE UPON A TIME, WAY BACK IN THE 1990’S, TWO OL BOYS WERE HUNTING IN THE COLORADO MOUNTAINS. IT WAS A WINTERY DAY AND PRETTY CHILLY OUT, HOWEVER, THE SKY WAS CLEAR AND THE SUN WAS SHINING DOWN, BLESSING ALL WITH ITS TOUCH. AFTER AN UNSUCCESSFUL MORNING CONSISTING OF MUCH BAD LUCK AND WASTED EXERTION, THEY FELL HUNGRY AND DECIDED TO GO BACK TO THE PICKUP TRUCK TO FEED. NOW THIS WAS THE GET-STUCK-EVERY-TIME-YOU-DRIVE-IT-ANYWHERE-4X4-PICKUP TRUCK, BUT THAT IS ANOTHER STORY. ONE OF THE OL BOYS WAS RECENTLY FROM OKLAHOMA AND POPULARLY CALLED “OKIE” AND WAS BOISTERIOUS AND EXTRAVERTED AND WAS THEREFORE DELCARED TO BE A LITTLE TAINTED, TO SAY THE LEAST, AND THE OTHER OL BOY HADN'T BEEN BACK TO OKLAHOMA IN SO LONG THAT HE DIDN'T HARDLY HAVE ANY TAINT LEFT ON HIM AND HAD LOST ALL OF HIS HILLBILLY ACCENT AND WAS SHY AND TIMID AND QUIET AND UNASSUMING AROUND PEOPLE, SO THEY CALLED HIM “UN-OKIE”. NOW, FOR LUNCH, THEY HAD BOTH BROUGHT A BOX OF AUTHENTIC SURPLUS U.S. ARMY MRE'S, (BETTER KNOWN AS: MEALS, READY TO EAT), NOT BECAUSE OF THEIR CULINARY PROPERTIES, BUT BECAUSE THEY WERE A SEMI-NOURISHING HOT MEAL, SIMPLE TO PREPARE AND EAT WHILE HUNTING, FISHING, OR JUST PLAIN ENJOYING THE GREAT OUTDOORS. THE BOYS SAT IN THE PICKUP TRUCK PREPARING THEIR MRE’S USING THE HEATERS INCLUDED IN EACH FOOD PACKAGE. IF YOU HAVE NEVER USED THESE MODERN MARVELS, LET ME EXPLAIN HOW THEY WORK. IN THE MRE BOX, YOU GET A LITTLE FLAT PACKAGE THAT YOU TEAR THE TOP OFF AND POUR IN A MEASURED AMOUNT OF WATER. YOU FOLD THE TOP OVER ON ITSELF AND IT BEGINS A CHEMICAL REACTION - VIOLA- IT HEATS ITSELF UP. YOU PLACE THIS PACKET INSIDE THE SMALL BOX WITH YOUR ENTREE AND IT HEATS UP THE FOOD. THIS WHOLE PROCESS TAKES 3, 4, OR 5 MINUTES, BUT SOMETIMES THESE HEATERS WON’T WORK, SO YOU JUST DISCARD THEM AND GET ANOTHER ONE GOING. WELL, THE OKIE BOY TEARS THE TOP OFF HIS HEATER, POURS THE WATER IN, AND WAITS TO SEE IF IT IS GOING TO WORK. MEANWHILE, AS THE ENTREE IS HEATING, YOU HAVE TIME TO PREPARE THE REST OF YOUR MEAL, TEARING OPEN THE SMALL PACKAGES OF CONDIMENTS, ETC. SITTING IN THE PICKUP TRUCK, GETTING THEIR MEAL SPREAD OUT, THEY USED UP ALL OF THE SMALL SPACE ALLOTTED EACH OTHER.
THE UN-OKIE, WISE IN THE WAYS OF THE OUTDOORS, HAD HANDILY AND EASILY PREPARED HIS HEATER AND SITUATED HIS LUNCH. ALL OF A SUDDEN OUT OF THE CLEAR BLUE SKY (AND TO THE VAST SURPRISE OF THE UN-OKIE, AS HE WAS BUSY GAWKING AT THE LANDSCAPE AND PREOCCUPIED WITH THE QUIETRY OF THE MOMENT AND HIS THOUGHTS), THE OKIE LOUDLY AND BOLDLY EXCLAIMED (MALICIOUSLY AND WITHOUT CANDOR) “THIS (EXPLICITIVE) HEATER DOESN’T WORK, I SHALL JUST HAVE TO PREPARE MYSELF ANOTHER (EXPLICITIVE) ONE”.
SUBSEQUENTLY, THE OKIE, INSTEAD OF PROPERLY DISCARDING THE OLD, NON-WORKING HEATER (BECAUSE HE ALREADY HAD HIS LUNCH SPREAD OUT EVERYWHERE, AS PREVIOUSLY DESCRIBED) HE CARELESSLY AND WITHOUT USING EVEN A SLIVER OF GOD GIVEN, EVERYONE’S BORN WITH, GREY BRAINMATTER, PLACED THE NON-WORKER ON THE SEAT BESIDE HIS LEG. HE THEN RUMMAGED AROUND AND FOUND ANOTHER HEATER, TORE OFF THE TOP, CAREFULLY MEASURED HIS WATER POUR, AND FOLDED THE TOP OVER ON THE PACKAGE, IMPATIENCE TANGIBLE IN THE CLEAR MOUNTAIN AIR. AFTER THE INITIAL SHOCK AND SCARE ANTICS OF THE OKIE, THE NON-OKIE SETTLED DOWN AND WAS BUSY ENJOYING HIS DELICIOUS HOT BEENY-WEENIE LUNCH, KEEPING A WATCHFUL HUNTING EYE ON THE BEAUTIFUL COLORADO LANDSCAPE. THE OKIES SECOND HEATER STARTED TO BOIL SO HE PLACED IT IN THE ENTRÉE BOX AND LAID IT ON THE DASHBOARD AND JOINED THE NON-OKIE IN LETHARGICALLY LOLLYGAGGING AND COLLOBORATING THE STORY THEY WOULD TELL THEIR WIVES, CHILDREN, FRIENDS AND CO-WORKERS ABOUT THE BIG ONE THAT GOT AWAY THIS DAY. IT WAS A MORE OR LESS LAZY, UNASSUMING AFTERNOON, QUIET IN THAT SPECIAL WAY THAT ONLY THE HIGH COUNTRY CAN BE, WITH THE WARM SUN BEAMING DOWN AND THE MARMOTS CHIRPING IN THE NEAR DISTANCE. ALL IN ALL, A VERY PLEASANT EXPERIENCE, NOT KNOWN TO MANY CITY FOLK, OR OTHERS NOT ACQUAINTED WITH THE MANY AND VARIED WAYS OF NATURE. ALL OF A SUDDEN THE OKIE JUMPED STRAIGHT UP INTO THE AIR, FOOD FLYING EVERYWHERE AND UNLEASHED A FLURRY OF EXPLETIVES. HE CONTINUED HOPPING UP AND DOWN FOR A WHILE (BETWEEN THE SEAT AND THE ROOF), JERKING AND SLAPPING AT HIS LEG. HE THEN FLUNG OPEN THE DOOR OF THE PICKUP TRUCK AND BEGAN TO SLAP AND PULL AT HIS BRITCHES LEG, ALL THE WHILE YELLING AND CURSING SOMETHING AWFUL.
THE UN-OKIE WAS STARTLED AND VERY MUCH ALARMED AT THIS BEHAVIOR AND READY TO BOLT, UNTIL IT DAWNED ON HIM WHAT HAD HAPPENED, AT WHICH TIME HE SPILLED HIS LUNCH ALL OVER HIS SIDE OF THE PICKUP TRUCK, BENT OVER AND HEAVING IN GREAT FITS OF LAUGHTER. WHAT WITH ALL THE OKIE’S SQUIRMING AND FIDGETING AROUND, THE NON-WORKING HEATER HAD MANAGED TO WEDGE ITSELF UNDER HIS LEG AND HAD COME ALIVE AND THE STEAMING HEAT HAD PENETRATED SEVERAL LAYERS OF CLOTHING AND WAS SCALDING HIS LEG. HE COULDN’T SEEM TO PULL THE HOT CLOTHING OUT FAR ENOUGH FROM HIS LEG TO ESCAPE THE FURY. THIS SPECTACLE LASTED A WHILE, WITH THE OKIE HOPPING AND JUMPING AROUND THE COUNTRYSIDE, LOUDLY SCREAMING AND CURSING, SCARING AND SCATTERING ALL THE WILDLIFE SOMETHING TERRIBLE, AND THE UN-OKIE LAUGHING, SNIGGERING AND GAGGING UNINTELLIGIBILY, SNOT AND TEARS INTERMIXED AND STREAMING DOWN HIS FACE, LUNCH SPILLED AND MASHED TILL IT WAS PICNIC ANT FODDER. OKIE FINALLY CALMED DOWN, AND EMBARRASEDLY DELCARED “WEREN’T HUNGRY NOHOW” AND SULKED AND WENT HUNGRY THE REST OF THE DAY, KNOWING IN THE BACK OF HIS MIND AND WITH HIS HEART OF HEARTS, THAT EVEN THE SMALLEST DETAILS OF THIS DAY WOULD NOT BE FORGOTTEN BY THE (SOMETIMES LOOSE LIPPED) UN-OKIE, AND RUEFULLY AWAITING THE DAY THIS STORY WOULD COME TO LIGHT. SADLY, BEFORE THE SUN SET ON THIS DAY, WAY BEFORE THE HUNTERS ARRIVED HOME, THE UN-OKIE WAS TREATENED WITH MANGLEMENT AND/OR DEATH OR BOTH, FOR THE TELLING OF THIS TRUE COLORADO HUNTING STORY, WHICH HAS NOW BEEN PUT TO PAPER AND SHOULD NEVER BE FORGOTTEN NOR MALIGNED IN THE RETELLING. AYE, IT SHOULD BE HAILED AS AN EXCELLENT EXAMPLE FOR THE NEXT GENERATION OF OKIE HUNTERS TO PONDER AND LEARN FROM, SO THAT THEY WILL NEVER HAVE TO EXPERIENCE THE SAME TERRIBLE MISTAKES AS THESE TWO EARLY LATTER DAY PILGRIMS.

Used properly, it is my experience that they work pretty well. My son-in-law, former Marine, says that you can also dig a shallow hole, pour the water into the heater, fold the top real tight, place it in the hole, and then cover it with dirt. In a little while you will get a nice "explosion,", the dirt on top of the heater flying a little way into the air...

it's possible that you have the old-style heaters that take longer to get warm and it looks like the new ones have a shelf life of 5 yrs.... http://www.mreinfo.com/mre-frh.html

Made in 1992, and at 15 it still made some heat. Not bad for a product that has a 10 year shelf life. Get the recent production ones- they aren't as messy, and they won't suck becuase they are still usable for their intended purpose. At this point, any left over from 1992 are a cute gag for a chemistry class and that is about it.

As for going boom and catching fire, what happens is that the chemical reaction that creates the heat also releases hydrogen gas. If you are stupid and do something like break one of these in half and use it heat your ration, then put the other half in your pocket, you are going to get burned. If you are stupid and crush one up and put it in a soda bottle to make a heater bomb, you could be injured, blinded, deafened, or all the other things that can go wrong with improperly used fireworks. And if you store them improperly in a room without ventilation, particularly if they've been down checked due to tears in the packaging as in the version of the story I think you are referring to, then yes, you can drown on dry land from these, but it would take a lot of them.

Read and follow the directions, or you or someone else gets a visit from Mr Darwin and the Gene Pool Police.

I guess that explains why the MRE heaters did'nt work properly. Being chemical heaters I thought that such an item would have an unlimited shelf life. It must be that the active chemicals - food grade iron and magnesium and sodium slowly oxidize over time loosing its ability to get the chemical reaction going. I suppose I'll just stick with something a bit more reliable, a bit lighter, a bit smaller, a bit quicker, not messy, which has a longer shelf life and something that can brew up a nice cup of hot sweet tea as well at the same time.


Alpkit Mytimug

Optimus Crux Stove (Excellent Swedish design again)

Folding Titanium Spork

And a standard 110gm resealable Gas Cartridge which all fit into the Mytimug along with Teabags, Whitener and Sugar.

Its not so much that they have a shelf life as it is that completely gas tight packaging is really, really hard to make. And expensive. And heavy. Some water vapor gets into them over time, and slowly degrades the performance.

And I like that stove. Tiny. But I can't picture a 110g cartridge- how big is it assembled?

If you add a little hot sauce to it, before adding water, then seal it tight, you get a lice little tear gas bomb, thats quite effective clearing a tent. Boredom can be fun!

Re Ironraven - Gas Cartridge

Sorry, the gas cartridge is referred to as a 100gm Cartridge not 110gm - it actually contains 97gms of 70/30 butane/propane.



Total Weight for the whole package is as follows

Mytimug - 127 gms
Optimus Stove - 87 gms
Gas Cartridge - 160 gms (contains 97gms of Fuel)
Folding Spork - 15 gms

Total Weight - 389 gms or less than 14 oz (equivalent to about 8 or 9 MRE heaters)

This setup would last about 2-3 days covering all cooking requirements and is much more flexible than MRE chemical heaters in that tea, coffee, hot chocolate and soups etc can be prepared.

Total Package size - as the cartridge and stove and spork fit into the Mytimug the package is 100mm (4') high and 90mm (3.5') in Diameter (smaller than 8 or 9 MRE heaters)

A good discussion of fuel efficiency and the pros/cons or various types of fuel is available at http://www.bushwalking.org.au/FAQ/FAQ_Efficiency.htm

I may have to look for a US source for the stove, I know I can get the fuel.