These machines are very easy to use and require little maintenance. Other than the occasional wipe-down to remove excess dust and debris, there are two filters within the concentrator. The first filter you’ll see on the back is the pre-mesh filter. This can be removed and rinsed as needed with warm soapy water and allowed to dry completely before putting it back on the machine (much like your vacuum’s sponge filter). Behind the pre-mesh filter is the Box filter, which does not need to be replaced until you’ve reached 5,000 hours (the hour-meter is the small digital display on the side of the unit) or one year of steady use. The Small and Medium Oxygen Cages require a flow rate of at least 5 liters per minute. The Large Oxygen Cage requires a flow rate of 10 liters per minute.