a month or so ago, I decided to put some staple food goods into 5 gal buckets for some long term storage, primarily just to see what process worked, and at what cost...most of the videos I viewed showed the use of mylar bags to block light, and dedicated oxygen absorbers sealed in the bags, but seems like the quantity packaging of the O2 absorbers almost necessitate a 10 bucket string, not a few packages at a time I wanted to try (I know you can store the unused O2 absorbers in glass jars, but there was not a local vendor for the mylar/O2 absorbers outside of the internet) ....I picked up a couple of the gray opaque buckets from Lowes and lids from Home Depot (the Lowes lids did not have a gasket) I recently purchased a vacuum food sealer, and set about to repackage an earlier bucket into which I had dropped an iron powder hand warmer... when I removed the handwarmer it was cold...I vacuum sealed the contents, and when I went to throw the hand warmer away, it was warm again...evidently it had worked, and the reaction stopped when the oxygen in the bucket had been used up....I repackaged the two buckets, added a warmer to each of the buckets... today when I looked at them, the lids are concave, and a slight concave crease in the side of the bucket where the air pressure inside is less than outside...I didn't check the barometric pressure the day I sealed the buckets,but looks like the handwarmers work to remove O2... just thought I would pass on an observation

On the face of it it doesn't sound like a bad idea. Save some money and double-down on the utility of hand warmers. I loves me some cheap utility.

But I don't know as how I would use hand warmers for oxygen removal in long term storage situations. The ones that might sequester oxygen either burn something, charcoal or lighter fluid, or react oxygen with iron using salt water to speed it up.

I'm not sure that water in a sealed container is the way you want to go. It also has to be pointed out that one of the main products of combustion is water. Doesn't sound like a good idea.

The burning of any common fuel does indeed produce water, which is about the last thing wanted in sealed storage.
Common fuels are all mixtures or compounds of hydrogen and carbon, when burnt they produce water and carbon dioxide.

Chemical hand warmers come in various types, some slowly burn small amounts of lighter fuel or charcoal, these would not be suitable.
Other types contain iron powder in a sealed pouch or other container. These should be suitable, they react iron with oxygen to produce iron oxide, no water is produced.
Iron oxide can be corrosive in the long term, I would be inclined to place the handwarmer in a peforated rigid plastic container in order that it may not contact the stored goods.

One drawback of any oxygen absorber is that the removing of the oxygen from the air in the container reduces the volume of the air by about 20%.
This causes stress on the walls and lid of the container and in the long term may lead to cracks, fractures, leaks or distortion.
It might be worth briefly and slightly opening the container after a few days in order to eqaulise the pressures. This will of course admit more air containing more oxygen, but a large enough oxygen absorber should absorb this as well as the first lot.
After the second and final sealing of the container, the pressure within will again drop as the oxygen is absorbed, but this time by only about 4% rather than by about 20%.
The effects of this may be minimised by finally sealing the container on a very cold day, or after storage in a refrigerator.

adam2... I equalized the pressure when I noticed the differential(there was a definite air rush into the buckets), will check them again in a day or so... the goods were vacuum packaged inside the buckets...I'm going to reduce the amount of iron powder to decrease the volume of O2 consumed for future attempts (due to the irregular shape of the vacuum packs its difficult to determine the exact internal volume, or I could use the PV =nRT gas law formula to determine the amount of iron needed).. for future reference I'll try a bag and 1/2 bag on an empty bucket to satisfy my curiosity

If I did the calculations correctly... a 5gal bucket has about 3.8liters of oxygen contained in the 19L of volume of the air(O2 is about 20% of air)...corrected to 25C and 1 ATM that is .16mol of O2... assuming a mix of +2 and +3 oxidation state for the iron it needs about 15g of iron powder, assuming 100% reaction rate

Perhaps set off the heat pack and let it run for a while before you put in into the container ? If you let it run for (say) 2/3 of its rated hours before you seal it in, you may get less pressure.

[quote=Aussie
Perhaps set off the heat pack and let it run for a while before you put in into the container ? If you let it run for (say) 2/3 of its rated hours before you seal it in, you may get less pressure.
[/quote]

Dont think that would help.
The idea is to remove all the oxygen, or it at least as much of it as possible.
Since air contains about 20% oxygen, the removal of this will unavoidably reduce the volume of the remaining gas to about 80%.

To avoid a partial vacuum in the container, more air must be admited, and the oxygen in this additional air must also be absorbed.

If the handwarmer is partialy expended before the container is sealed, then it might still have sufficient capacity to absorb all the remaining oxygen, and produce a partial vaccuum as above.
Alternatively the partialy expended handwarmer might be able to only remove part of the oxygen, this would reduce the degree of vaccuum produced, but would be a bit pointless since the object of the exercise is to remove all/as much as possible of the oxygen.

Adam2 - Good point.

In winemaking we pump CO2 into tanks to exclude air and prevent oxidation, but generally we have special valves to allow the CO2 in and air out. Potentially you could mount a valve(s) on the lid of the container and pump CO2 in, air out ?

Seems a bit messy, but it depends what you want to do.

- Just a thought ...

I thought that when you used CO2, it was heavier than regular air and would settle to the bottom of the container, gradually expelling the oxygen? Would you really need to pump it out?

Sue

Yes you're correct, the CO2 is liquefied under pressure so it just flows in, its not actually "pumped".
It does settle to the bottom of the tank (or sits on top of the wine), which displaces the lighter air mix. Because there is a venting valve at the top of the tank, the air is pushed out and eventually the entire volume is filled with CO2.

A fancy setup can actually monitor the gas pressure and automatically top it up as needed.

Probably a bit fancy for a 5gal bucket, but I have heard of people using soda siphon bulbs to inject CO2 into smaller wine vessels, but I’m not sure exactly how.