Track 4 РDISPOSABLE FILTER 

Track 4 is an extension to track 3. Thee mentioned sequence is extended with collecting used masks, and clean them with dedicated equipment and or facilities.

Track 4 can also be used to absorb disposable masks from track 1 or track 2, so these can be cleaned 2x or 3x as long as new supply from track 1, 2 or 3 is insufficient.