What substance consumes oxygen from atmospheric air
As mcole's comment suggests, it may be easier to do this by physical rather than chemical means.

There are two common approaches:


  Purge


In the purge method, the vessel is filled from a high pressure source of another gas. The air needs some way to escape. If the new gas is more dense, all the better, but even repetitive purges of less dense gases will eventually push all the air out.


  Pump and backfill


In this method, the vessel is connected to a vacuum pump, and the air inside is pumped out. The vessel is then refilled with an inert gas. Depending on your needs, you can repeat this process several times.