The little sachet is the part of long term food storage that people understand least and worry about most. It arrives in a vacuum packed bag of a hundred, the instructions say to work quickly, and the number on the front is in cc, which is a unit nobody uses for anything else in a kitchen. Then you are standing over an open bucket wondering whether one is enough.
Oxygen absorbers are simple once the units make sense. This guide explains what cc actually measures, gives the sizing that suppliers publish for common containers, and covers the foods that should not get one at all.
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Quick Answer
What size oxygen absorber do you need?
- The cc rating is the volume of oxygen the sachet can absorb, not the size of the container it fits.
- Absorber suppliers publish roughly 300cc per gallon of container volume, and 2000cc for a filled 5 gallon bucket liner.
- Going over is harmless. The iron simply stops reacting once the available oxygen is used up, so err upward rather than downward.
- Dry foods only. USU Extension warns that removing oxygen increases the ability of botulism bacteria to grow, which is why moist products stay out.
Bottom line: work from container volume, round up rather than down, and keep them out of salt, sugar and anything moist.
What cc Actually Means
The number is capacity, expressed in cubic centimeters of oxygen the sachet can chemically absorb before it is spent. It is not a container size and not a weight of food. A 300cc absorber will handle roughly the oxygen in a gallon of air, which is why the standard guidance works from container volume rather than from what is inside it.
Inside the sachet is iron powder. It oxidizes, which means it rusts in a controlled way, and in doing so it takes oxygen out of the sealed space. That reaction generates a little heat, so a sachet that feels warm in your hand is working rather than faulty.
Why Food Volume Does Not Change the Math Much
A bag of rice is not solid rice. Air fills the gaps between the grains, and that trapped air is a meaningful share of the bag volume, which is exactly why sizing is done on the container rather than on how full it looks. It is also why an oxygen absorber outperforms a vacuum on dry goods, since no pump reaches the air between individual grains.
The Size Chart
| Container | Common absorber size | Typical contents | Note |
|---|---|---|---|
| Quart mylar bag or jar | 100cc | Spices, seeds, dehydrated vegetables | One is plenty at this volume |
| Half gallon jar or bag | Around 200cc | Portioned grain, snacks | Two 100cc sachets work equally well |
| 1 gallon mylar bag | 300cc to 500cc | Rice, beans, oats, flour | Suppliers often recommend the higher figure for packed food |
| 5 gallon bucket liner | 2000cc | Bulk grain and legumes | Suppliers list 2000cc to 2500cc for a filled liner |
These figures are the sizing that oxygen absorber suppliers and mylar bag manufacturers publish for their own products, and they are packaging guidance rather than a food safety standard. When a listing gives its own recommendation for the sachets you bought, follow that listing.
Oxygen Absorbers by Container
The Everyday Gallon Size
300cc is the workhorse, because gallon bags are the size most households actually pack. Buying a hundred at once is normal, since they come vacuum packed together and you cannot open the pack for one sachet and expect the rest to keep indefinitely.
Bucket Liners
2000cc sachets are made for a filled 5 gallon bag inside a bucket, and one per liner is the usual guidance. If you are packing several buckets in a session, count out exactly what you need before opening the pack, because the clock starts as soon as air reaches them.
Small Bags and Jars
100cc sachets suit quart bags, spice jars and portioned snacks, and they let you pack many small containers from one bag of absorbers. They are also useful for topping up: two small sachets in a gallon bag do the same job as one larger one.
When the Problem Is Moisture Instead
Desiccants remove water vapor, absorbers remove oxygen, and they are not substitutes. If you are storing something already dry in a humid climate, a food grade silica gel packet alongside the absorber protects against moisture creeping in from handling and packing. Do not use a desiccant instead of an absorber.
What Should Not Get an Absorber
Salt and sugar are the two obvious exclusions. Neither needs oxygen removed, and an absorber inside a sealed bag of granulated sugar can leave you with one solid block. Bag them for pest and moisture protection and skip the sachet entirely.
Moist foods are the serious one. Utah State University Extension states plainly that vacuum packaging increases the ability of the botulism bacteria to grow by removing oxygen, which is why reduced oxygen packaging is limited to genuinely dry, low moisture products. Home dehydrated food that is still pliable or tacky does not qualify.
Oily Foods Are a Partial Case
Removing oxygen slows the rancidity that ruins nuts, whole grain flours and brown rice, so an absorber helps. What it does not do is make an oil rich food keep like white rice, because the fats degrade over time regardless. Store oily items in smaller portions you will actually get through.
Handling Them Without Wasting the Pack
An absorber starts working the moment it meets air, so the sequence matters. Fill all your bags first, line them up, then open the absorber pack, drop one in each bag and seal as you go. Do not open the pack and then start filling bags.
Whatever you do not use goes straight into an airtight jar, ideally a small canning jar with a lid you can close in one motion, or a resealed vacuum bag. Left on a counter they quietly exhaust themselves and are then just sachets of rust.
Checking That They Worked
Come back to a sealed mylar bag after a day. If the bag has drawn in tight against the food and the corners have pulled in, the absorber consumed the oxygen inside and atmospheric pressure did the rest. A bag that is still loose and puffy after a day points to a leaking seal, a spent absorber, or one that was too small for the volume.
Frequently Asked Questions
I have no idea which cc size to buy, how do I choose? Work from container volume, not food weight. Suppliers publish roughly 300cc per gallon of container and 2000cc for a filled 5 gallon bucket liner, with 100cc suiting quart bags. When in doubt, go up a size.
Can I use too many oxygen absorbers? Not in a way that harms the food. Once the available oxygen is used up the iron stops reacting, so extra capacity simply sits idle. The waste is your money rather than your storage.
What is the difference between an oxygen absorber and a desiccant? An absorber chemically removes oxygen; a desiccant removes water vapor. They solve different problems and neither substitutes for the other. Dry goods in a sealed bag usually want the absorber, with a desiccant added only where humidity during packing is a concern.
Do oxygen absorbers work in glass jars? Yes, provided the lid actually seals. A canning jar with a fresh two piece lid or a good gasketed lid holds the reduced oxygen environment, and you will often hear the lid pull down as the absorber works.
My absorbers got warm, is that a problem? No, that is the reaction. The iron oxidizing produces a little heat, which is one of the few visible signs that a sachet is live rather than spent.
Can I put an absorber in with brown rice or nuts? You can, and it slows oxidation, but do not expect the same longevity as white rice. Fats degrade over time whether or not oxygen is present, so keep oily foods in portions you will use.
The Bottom Line
Size an oxygen absorber to the container volume, not the food, using the figures suppliers publish for their own products: around 300cc per gallon and 2000cc for a filled bucket liner. Going over is harmless and going under is the one mistake that quietly costs you the batch. Keep them out of salt and sugar, keep them out of anything moist, and store the unused ones sealed. Next: the mylar bags guide for the bag that goes around them, and the food storage buckets guide for what goes around that.