What You Need to Know
The iron powder in the scavenger reacts with residual O₂ to form iron(III) oxide (Fe₂O₃), following the reaction 4Fe + 3O₂ → 2Fe₂O₃. This reaction removes oxygen at a rate of ~0.1 mg O₂ per mg iron per day at 25 °C, and the rate declines as the iron oxide layer thickens.
The Science
Primary Reaction
4Fe + 3O₂ → 2Fe₂O₃