The baghouse filter is step 3 in the purification process. These filters each consist of 768 long, plastic sleeves which are suspended from a frame. This results in a fabric with a surface area almost as big as a football pitch. The flue gases enter the filters at the bottom and leave the bag filters at the top, cleansed of dioxin, furans and heavy metals. After this step, over 99% of the dust particles will also have been filtered out of the flue gases.