Grain, pellet and multi-fuel appliances require regular maintenance. Grain, pellet and multi-fuel appliance manuals ussually recomend a "maintenance" schedule that should be used as a guideline for cleaning. You never should maintain your appliance less than what the manufacturer suggests. Depending on the fuel quality (ash content, moisture and inorganic material) and the amount of fuel being burned, more maintenance maybe required. Inadequate maintenance may result in inadequat draft which can cause the appliance to over fill the firepot, sooting, excess smoke and possible hopper fires. In a properly maintained appliance the flames should be yellow and or white in color. In an in-correct flame situation, the fire will have tall lazy flames that will be yellow / orange in color with black tips and or smoke coming off the flame. There should be no black tips or smoke coming off the flame.