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