Dust is the enemy of 3D printing and steps must be taken to prevent this entering the extruder and passing through to the nozzle at the end of the hotend, Assuming that quality filament is used then preventing dust and contaminants from entering the extruder will remove the main cause of nozzle blockage.
This filament cleaner can be used in line or depending on the printer version, it can be secured to the printer by means of the holes in the body in which case it can also act as an anchor point for PTFE feeding the filament. to the extruder
The cleaner has a hole at each end for the filament to pass through. Inside the cleaner body "magic sponge" (recommended and supplied ) or some other cleaning material is placed so that any dust on the filament as it enters the cleaner is trapped as the filament passes through. the cleaning materiel should be cleaned / replaced as necessary.