did a search, didn't find much.

Online resources suggest "one" 500cc packet per 5 gal bucket, ARCOM wizards suggest doubling up each back to ensure proper utilization.

These will likely be stored (long grain white rice) for years before I feed them to my kids in the following condition:

single large mylar bag (sealed) inside a home depot bucket and rubber-gasket lid, in a cool basement.  Expectation of 5 years.

Suggestions?   I have 500cc and 100cc 02 absorbers I havne't opened yet - going to do 4-5 buckets at a time.   I was planning on one 500cc per bucket and then checking for "vacuum" so to speak after a few days, before sealing the buckets.

I believe the general consensus is 1500cc of o2 absorbers for 5 gallon buckets (I could be wrong). There is a website that shows how many cc's per type of bag/bucket (I'll see If I can find it if someone else doesn't post a link). Also, If you seal the bags well with the proper amount of o2 absorbers - you can quadruple that 5 year anticipated shelf life.

ETA - http://www.sorbentsystems.com/o2absorbers_1.html

I  toss in a small hand warmer, it pulls a good vacuum, pulling the lid down concave.
With a couple of these, you could do a 55 gallon drum if you wanted to.

Hand warmers go on sale at Wally-world in the spring.

ETA:  The answer is....

2 500cc packets  

from the above link, their example was exactly what I was looking for (thanks!).   They calculated that a 5 gal bucket of rice would need less than 700cc of O2 absorption...  so 2 500cc'ers will be more than enough.

Ok, so handwarmers work on (absorb) oxygen, I get that. But are these a commonly acceptable substitute for O2 absorbers?

I'm just wondering because that seems like a pretty cheap source of O2 absorbers if you can find them on sale.

Any negative effects from the "burst" of localized heat that is trapped inside a bag that reflects the radiation back in? There is basically no convection or radiation to get rid of heat which are the 2 major heat dissipators in this situation; and rice/grain is a pretty decent insulator so very little conduction.

They don't get hot... they only get warm while it absorbs the oxygen, and should not affect the grain.
From what I understand, the 02 absorbers and the hand warmers are made of powdered iron and salt.

A reminder about 02 absorbers, if the packet is " stiff " ( not flexible with loose material inside )... it's probably shot.
I store them in an air tight jar.

There's more on this kind of stuff all the time, come on over to the survival forum -> http://www.ar15.com/forums/forum.html?b=10&f=17