Humidifiers that run constantly benefit from weekly cleanings. Unplug the unit and remove the filter, rinsing or replacing as needed. Pour undiluted white vinegar into the base and allow to stand for 15 to 30 minutes. Scrub gently with a soft scrub brush and rinse with plain water. For warm-mist humidifiers, gently brush away any mineral buildup on the heating element. Dry and replace the filter.