In my book, The Prepper’s Cookbook: 300 Recipes to Turn Your Emergency Food into Nutritious, Delicious, Life-Saving Meals, ” I go into a detailed explanation about how to use this essential food storage tool and how much is needed.
What Are They and How Do I Get Them?
Oxygen absorbers  are small packets that contain an iron powder. The packets are made of a material that allows oxygen and moisture to enter but does not allow the iron powder to leak out. Oxygen absorbers can greatly prolong the shelf life of stored food by inhibiting the growth of aerobic pathogens and molds. If you live in an area prone to high humidity, you may also want to consider adding desiccant packets to your food storage. When you receive your oxygen absorbers in the mail, they will be enclosed in vacuum-sealed packs. It is important to keep them in an oxygen free environment until you are ready to use them.
What Do They Do?
When using oxygen absorbers you need to be a bit methodical in your food storage planning. Once opened, they begin absorbing oxygen the moment they’re exposed to it, so it’s best to work as efficiently as possible. The best way I have found to use this storage tool is to pack all my food in the container and when they are ready to be sealed, I will open the oxygen absorber packet and grab the desired amount of packs then seal the remaining oxygen absorbers up for future use. Then, I will add the absorbers into my ready-to-be sealed food storage containers and seal.
How Do I Correctly Use Them?
To determine how many cubic centimeters your oxygen absorber should be, it’s important to consider the type of food being packed. Requirements vary depending on the volume of the food, the “void space” (the space between food particles), and the “head space” (the container space not filled with food). For example, if you fill a 5-gallon bucket all the way to the top with marbles, leaving no head space, the void space is the amount of air between marbles. Because marbles don’t pack as densely as, say, salt, your bucket will require a larger oxygen absorber than a 5-gallon bucket of salt.
This is the general formula for the cubic centimeters of oxygen absorption required:
Container volume – Food volume = Residual air volume
Residual air volume x 0.21 (because air is 21% oxygen) = Oxygen absorber size requirement
You want your oxygen absorber to meet or exceed the residual air volume in the packed container. Here’s how it works. If we’re packing 35 pounds of rice in a 5-gallon bucket, an online calculator tells us that 35 pounds of rice is equivalent to 15,875 grams (or cubic centimeters). Our 5-gallon bucket is equivalent to 18,942 cubic centimeters of air volume. Assuming the rice fills the bucket to the top, leaving no head space, we can calculate the void space (oxygen absorber size requirement) as follows:
Note* = 1 gram is equivalent to 1 cc, so the result will always be equal
This calculator  can be used to convert pounds to grams
This calculator  can be used to convert grams to cubic centimeters (cc)
18,942 cc (container volume) – 15,875 cc (food volume) = 3,067 cc (residual air volume)
3,067 (residual air volume) X 0.21 (oxygen) = 644 cc (oxygen absorber size requirement)
The following chart is a guide to the oxygen absorber sizes you’re likely to need for some food you’ll be packing. The chart assumes that containers are full and that as much air as possible has been removed. (Vacuum sealing is recommended when possible.) Oxygen absorbers are typically sold in 50, 100, 300, 500, 1,000, and 1,500-cc sizes. Since head space and void space can’t be calculated exactly, when in doubt it’s best to err on the side of caution and use a larger size, as has been done for this chart.
Oxygen Absorber Size Requirements
1-quart pouch (8″ x 8″)—947 CCs)
#10 can (0.82 gallon)—3,910 CCs)
5-gallon bucket—18,942 CCs
6-gallon bucket—22,730 CCs
|Flour, pancake mix, fine powders||50–100 cc||200–300 cc||750 cc||1000 cc|
|Sugar, salt, dry milk||50–100 cc||200–300 cc||750 cc||1000 cc|
|Rice, grains (wheat berries, oats, etc.)||50–100 cc||200–300 cc||750–1,000 cc||1000–1,500 cc|
|Dried beans||100–150 cc||300–500 cc||1,000 cc||1,500 cc|
|Pasta||100–200 cc||300–600 cc||1,000–1,500 cc||1,500–2,000 cc|
Keep in mind that some foods should not be stored with oxygen absorbers. Certain foods such as sugar and drink mixes in particular will become hard bricks or have significant clumping if oxygen absorbers are added to their packaging. This is because these foods need a certain amount of moisture in their environment in order to maintain their powder-like form.
Information in this article has been excerpted from the book, The Prepper’s Cookbook: 300 Recipes to Turn Your Emergency Food into Nutritious, Delicious, Life-Saving Meals  by Tess Pennington