Electric ignition stoves use electric sparks to ignite the surface burners. Two sherds have charcoal deposits indicating that these were once charcoal burners or stoves. Chemistry laboratories use natural-gas fueled Bunsen burners. HID burners give higher efficacy than halogen lamps. Candles or small oil burners are commonly used. Ceramic sculpture also includes incense burners and burial urns. Specialty equipment may be used, including salamanders, French tops, woks, tandoors, and induction burners. In 1904 the lamps were replaced with incandescent oil vapour burners. They have also been used as incense burners. C2 is for vaporising or atomising burners in appliances connected to flues. They often depict traditional Saudi items such as coffee pots, incense burners, palm trees, etc. Number 1 fuel oil is a volatile distillate oil intended for vaporizing pot-type burners. The flame is between the front and back burners. The transition required the adjustment of burners and airflow valves on 1.75 million appliances. This consisted of adding incense burners, candles, dimmed lights and pornography on the walls.