October 24, 2016

The Difference Between Oxygen Absorbers and Silica Gel

This post is by Bernie Carr, apartmentprepper.com

I was telling a friend who is new to preparedness about packing bulk foods for long terms storage, when she asked me if oxygen absorbers are the same thing as the little  packets you find in new purses and shoe boxes that say “Do not eat.”   This reminded me that I was confused about this at one time so I thought I’d do a quick post about it.

oxygen absorber
Oxygen Absorbers

Oxygen Absorbers

Oxygen absorbers are tiny sachets that contain iron filings, salt and clay.  The clay provides moisture, and works with the salt to activate the iron filings.  The process starts as soon as the oxygen absorber packets is exposed to oxygen.  What happens is the iron filings begin to oxidize, forming rust which then releases nitrogen.  Nitrogen helps the food keep fresher longer.  The lack of oxygen in the stored food will keep weevils and other insects from living in there.

Most oxygen absorber packs come with a little pink pill that turns blue if the oxygen absorber is no longer effective.  A few other notes about oxygen absorbers:

  • Sugar and salt for long term storage do not need oxygen absorbers as they will turn rock hard.
  • Once you open a pack of oxygen absorbers, take what you need and keep the rest in an airtight jar, not a plastic bag.  Keep their exposure to air as little as possible.  Otherwise they will all get activated and useless by the time you need them.
  • To be effective, you need to use the right number of oxygen absorbers for the food you are packaging.  This site has a handy chart on how much oxygen absorbers to use. (We have no connection to this site, just found the chart helpful.)
  • Oxygen absorbers cannot be reused.
Silica gel
Silica gel

Silica Gel

Silica gel is made of silicon dioxide, essentially, porous sand.  It is used to reduce condensation and allows the stored item to stay dry even during humid, damp conditions.  You find them in bottles or packages when you buy vitamins, purses, shoes, even computer equipment.  Because silica gel inhibits moisture, it therefore prevents mold to grow.

If you are packing a 5 gallon bucket with silica gel to keep moisture at bay, you will need a 10 gram silica gel packet.   Some items that can be packed with silica gel include:

  • photos
  • camera equipment
  • prescription and non prescription medicines
  • ammunition cans and gun cases
  • seed packets
  • tool boxes
  • luggage
  • important documents

Silica gel packets can be reused.

I haven’t tried it, but silica gel packets can be reactivated – see these instructions from eHow.

Can oxygen absorbers and silica gel be used together?

The answer is NO, they should not be used together.  The reason is, oxygen absorbers require moisture in order to work.  If the silica gel absorbs the moisture, it will halt the activation process of the oxygen absorber, rendering it useless.


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4 Comments on The Difference Between Oxygen Absorbers and Silica Gel

  1. Good morning sir; always liked your site, good article! A couple of notes if I may. The main way Oxygen Absorbers sequester oxygen is that the process of oxidation (rusting) requires oxygen. Nitrogen will be the main gas remaining in any Mylar bags after the oxygen is absorbed because it is 80% of air naturally, but absorbers don’t put off Nitrogen per se as part of their chemical reaction.

    While conventional wisdom has held that you shouldn’t use absorbers and desiccant together, our testing has shown they can be used simultaneously. However, we only recommend desiccant if you are storing at a humidity level above 30%, otherwise desiccant isn’t needed. Over that, and there is sufficient moisture to activate the absorbers while the desiccant removes the some of the remainder. As moisture is as (or more) damaging over time to shelf life, removing both is recommended.

    Great site!


  2. Great article. I haven’t used either in my food storage. I’m in Houston also. Humidity is a major menace for almost everything. As long as the A/C is on…. life is good. When it’s not…. it sucks.
    I need to take extra precautions…. there might come a day very soon when power is not available. Cheap packets of either product might just help keep some of that food lasting longer.

  3. Timely information for me! Thanks, very much. We use desiccant packs (silica gel) in all of our electronics storage, but I wondered about using them in food, since we live near the beach in California and the air is seriously damp here and mold grows everywhere. Now I know that the oxygen absorbers should be enough. Thanks again!

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