Tools · buyer's guide
The Best Oxygen Absorbers for Long-Term Food Storage (2026)
Oxygen is what makes stored food go bad. It turns fats rancid and lets weevil eggs and other pantry bugs hatch and live. Oxygen absorbers are small iron packets that pull that oxygen out of a sealed container, so dry staples like rice, beans, and wheat can keep for 20 years or more instead of one or two. Here is how to size them, how to use them right, and two picks worth buying.
Photo: Photo: Shixart1985 (CC BY)
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What oxygen absorbers do (and what they are not)
An oxygen absorber is a little packet of iron powder. Once you open the bag, the iron starts rusting, and that reaction eats the oxygen in the sealed space around it. Drop enough into a Mylar bag or food-grade bucket of dry food, seal it up, and the air inside drops to almost no oxygen. With no oxygen, fats do not go rancid and insect eggs cannot survive.
They are not desiccants. A desiccant, like the silica gel packet in a shoebox, pulls out moisture. An oxygen absorber pulls out oxygen and does almost nothing for moisture. Your food needs to already be dry before you seal it, because an absorber will not dry it for you.
How to size them: the cc rule of thumb
Oxygen absorbers are rated in cc, which is how much oxygen one packet can soak up. A common rule of thumb is about 300cc of absorber per gallon of dry food. So a standard 5-gallon bucket or bag holds roughly 5 gallons of food and needs about 1,500cc total. That can be one 1,500cc packet or a few smaller ones added together.
Going a little over is fine and gives you a safety margin, so people often round up. Going under is the real risk, because leftover oxygen means shorter shelf life and a chance for bugs to survive. When in doubt, add more.
Use them fresh and reseal fast
The moment air hits an absorber, it starts working, and it does not stop. So the packets you are not using right now have to go back into an airtight container within a few minutes, or they will use themselves up on the room air and be dead when you need them. Many people reseal the spare packets in a small jar with a tight lid.
A simple tell: good absorbers usually come with a small pink or blue indicator pill, or the packets feel soft and loose. Once they have soaked up all they can, the iron inside turns hard and warm to the touch. If a packet is rock hard before you use it, it is spent. Buy in a sealed, air-tight package and only open it when you are ready to fill containers.
When NOT to use them
Oxygen absorbers are for dry, low-fat food only. They are not a cure-all, and using them on the wrong food can be unsafe or just wasteful.
The big danger is high-moisture food. Removing oxygen from a moist, sealed, room-temperature container creates the exact low-oxygen condition where botulism can grow. That is why absorbers are for dry storage, and why wet food gets canned by a tested recipe or kept in the fridge or freezer instead.
Our picks
- Best overall for sizing to any container
Oxygen Absorbers (300cc), Bulk Pack
Best overall
- 300cc packets are the easy building block: one per gallon, five for a 5-gallon bucket, so you can dial in almost any size.
- Usually shipped in a sealed, air-tight bag with an indicator so you know they arrived fresh.
- Downside: once you open the master bag you have to use or reseal every packet fast, so buy a count you will actually go through, not a giant lot you open and let sit.
- Best for the airtight barrier the absorbers need
Mylar Storage Bags (with absorbers to match)
The other half of the job
- An absorber only works inside a real oxygen barrier, and Mylar bags give you that in a 5-gallon size that drops into a bucket.
- Thick, light-blocking film protects grains and beans for the long haul when heat-sealed shut.
- Downside: you need a hair straightener or an iron to heat-seal them well, and a weak seal lets oxygen creep back in and ruins the batch.
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Questions, answered straight
Use about 300cc per gallon of dry food. A 5-gallon bucket or Mylar bag needs about 1,500cc total, and a quart jar needs one 100cc packet. Round up if you are unsure, since extra capacity does not hurt the food.
An oxygen absorber is iron powder that pulls oxygen out of a sealed container so fats do not go rancid and bugs cannot live. A desiccant, like silica gel, pulls out moisture instead. Absorbers do almost nothing for moisture, so dry your food first.
Not really. Once a packet has soaked up its oxygen the iron inside is spent and turns hard. Spare unused packets can be saved only if you reseal them in an airtight jar within a few minutes of opening the bag, before they use themselves up on room air.
Skip high-moisture food (fresh produce, soft jerky, anything not fully dried), because removing oxygen from moist sealed food creates a botulism risk. Also skip high-fat food like nuts and brown rice, which go rancid on their own and keep better in the freezer.