Humidity from the packaged food causes the iron while in the oxygen absorber to rust. Mainly because it oxidizes, the iron absorbs oxygen. Oxygen absorbers rated for three hundred cubic centimeters (cc) of oxygen perform well for adequately packaged dry food in containers of up to one-gallon potential (four liters). http://dryfoodlyrics61594.collectblogs.com/22235256/facts-about-dry-food-bags-revealed