These models are heated by wire heating elements protected from chemical and mechanical damage by a high quality, hard wearing alumina based liner. The graded winding and powerful double sided heating elements compensate for the heat loss, as well as preheating the air prior to it entering the chamber. Temperature uniformity within the chamber is therefore excellent, despite the higher airflow through the chamber. The AAF 11/3 and AAF 11/7 have a large floor area which allows many samples to be accommodated and because of the low chamber height the airflow is held close over the samples to promote burning. High airflow of between 4-5 changes per minute is ensured by use of an air inlet and a tall chimney, however it is not too high to disturb the samples in the crucibles, or chill them, as the incoming air is preheated. The AAF range is ideal for ashing materials such as food, plastics, coal & other hydrocarbons. The AAF 11/7 furnace complies with the following industry standards BS 1016 part 4, ISO 344 and 1171, ASTM D2361, D2795 and D3174. The AAF 11/18 has high grade heating wire mounted behind silicon carbide tiles to protect against carbon or corrosive atmospheres. A two tier shelf is supplied as standard, which doubles the furnace capacity. An optional temperature programer available.