Decal says: YOU MUST SERVICE AIR CLEANERS DAILY 1 UNSCREW PLUG, REMOVE DUST 2 REMOVE FILTER AND WASH IN KEROSENE USING UP AND DOWN MOTION 3 SWING VIGOROUSLY THROWING OUT SURPLUS KEROSENE 4 SUBMERGE AND SOAK IN NEW OIL 5 SWING VIGOROUSLY THROWING OUT SURPLUS OIL 6 REPLACE OIL SATURATED FILTER 7 TIGHTEN COVER SECURELY