The removable metal columns provide a way to self-service your Inogen Rove 6 or Inogen One G5. Sold and used as a pair, the columns contain the sieve beds that convert normal air with lower levels of oxygen concentration to a high concentration of oxygen. These sieve beds wear down after prolonged use. The “replace columns” alarm will alert you when the (sieve) columns need to be changed, typically once a year. In certain operating conditions, earlier replacement may be required. The Inogen Rove 6 or Inogen One G5 will let you know when it is time for replacement. Step-by-step instructions enable you to switch out the column pair without tools – without having to send the Inogen system in for repair.