Checking the Capacity of Oxygen Absorbers

The following test was made with Fresh Pax D750 absorbers.

How do you know when an oxygen absorber is spent???

Generally, oxygen absorbers have a greater capacity than is listed on the package. This is intentional to allow for some exposure of the packet to air during your packaging process. None of this is necessary if you have a new, sealed bag of oxygen absorbers. However, if for any reason you want to check them, this is one way to get it done.
It’s impossible to see how much life is left in an absorber by looking at it or feeling it. The only sure way is to actually see how much oxygen it will absorb. One way to do this is to tape the absorber to the bottom of a bottle. The larger the bottle the better. In my tests I used a gallon pickle bottle. Put the bottle upside down inside a pan of water being careful to set it straight down so no water enters the bottle. As the days pass and the absorber takes in oxygen, the water level will rise in the bottle. When it stops rising, use a magic marker and mark the water level, then take the bottle out of the water and fill it with fresh, new air. I did this by blowing 5 or 6 full breaths of air into the bottle. Then sit it back down into the water. When the water level stops rising again, mark the level again then fill it with new air and repeat the process until the absorber won't pull any more water up into the bottle.
In my tests it took 3 1/2 cycles for the D750cc absorber to get loaded using a 1 gallon bottle.
The next step is to see how much air was absorbed. Pour some water into the bottle, put on the lid, and turn the bottle over. Add/remove water until the level lines up even with the top line you made with the magic marker. Turn the bottle right side up, remove the lid, and pour it into a container. Now, repeat the process for each of the other water level marks and add this water to the first water in the container. After you have finished, measure the amount of the total water you poured into the container and this will give you a pretty good estimate of the cubic volume of oxygen your absorber absorbed.
Realize this is not 100% accurate if you take the atmospheric pressure and air temperature into account. As the barometer or room temperature fluctuate, they will make the water level go up or down in your bottle independent of how much oxygen has been absorbed. If you have a barometer, you may also wish to record the barometer reading each time you finish a cycle. You can correct for temperature by making sure the room temperature where you are doing your test is the same temperature each time you complete a cycle. Altitude will also have an effect on how much water gets into the jar. The higher the altitude the higher the water will rise for the same amount of oxygen being absorbed. This is because the air is thinner the higher you go in elevation. If you wish to remedy this, use the following table to correct your reading for sea level.

Your Multiply absorbed Altitude volume by... Sea Level 0.0000 1,000 ft. 0.9706 2,000 ft. 0.9411 3,000 ft. 0.9160 4,000 ft. 0.8866 5,000 ft. 0.8613 10,000 ft. 0.7395 15,000 ft. 0.6203
In one of my tests a 750cc absorber displaced 2425cc water at 2,000 feet. Corrected to sea level, that’s 2,282cc water displacement. For that particular absorber, there was an actual capacity of 304% of it’s advertised rating, more than I expected.
A thanks to LDS Welfare Services who gave me this idea in the first place.

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