| 摘要 |
A filter medium (11) comprises at least a first (12) and a second layer (13) . Both first and second layer have a layer volume VLq and a layer filtering surface SLq, where SLq is the accumulation of all mantle surfaces of the fibers present in this layer q. The first layer has a SL1/VL1-raio of less than 32500 m /m~, and the second layer has a SL2/VL2-ratio being more than 1.1xSL1/VL1. |
