This is best accomplished by a professional service. Do not use green or treated wood. Air filters should be changed at least once a year and checked monthly when the furnace is in use. Check your fuel type. Check all settings and adjustments, including the wick type and height.
Larger heaters produce fewer PAH emissions than small ones due to greater burning efficiency.
Because air pollutants can reach high levels in the vicinity of their use, kerosene heaters should not be used to heat bedrooms at night EPA recommends four square inches of open window for each 1,000 BTU of heater capacity. Another suggestion is to use an electric heater instead of a kerosene heater. A portable humidifier may also add pollutants or microorganisms to the air. Use distilled water because minerals from ordinary tap water may become airborne during use. Change the water daily and follow the user's manual regarding cleaning products and disinfectants.