Maintenance Kit includes two filters, two fuses, 2 O-rings, one nozzle(1.0/80) and a nozzle wrench. 
The O-ring is found on the inside top of the filter housing.  Filters should be replaced every 300 hours of operation and every year. 

If unit is producing any smoke during regular operation the nozzle may be clogged and require replacement.
 (1.0/80 Nozzle)