Oxygen Absorbers are small packets that contain an iron powder. These packets are made of a material that allows oxygen to enter but does not allow the iron powder to leak out. When an oxygen absorber packet is removed from its protective packaging, the Oxygen molecules & moisture in the surrounding atmosphere begins to permeate into the iron particles inside of the absorber packets. Available moisture activates the iron, and it oxidizes to form iron oxide. Typically, there must be at least 45% relative humidity in the surrounding atmosphere before the rusting process can begin. To assist in the process of oxidation, sodium is added to the mixture. Sodium acts as a catalyst, or activator, causing the iron powder to be able to oxidize even with relatively low humidity.