What’s the difference? As you can see in the image, the materials prepared on the surface filtration block the particles on its surface, while those predisposed to deep filtration allow the penetration of the particles within its thickness. Frequently the accumulated particles behave as an additional filter element, and thus enable to increase the separation efficiency. It is important to point out that, compared to an increase of efficiency, there is also an increase of the pressure drop, which make necessary a cleaning or a replacement of the filter element. As you may have guessed, given the lower penetration of particles, the materials that promote a surface filtration are easier to clean and last for more over time. The materials that instead promote a deep filtration are more difficult to clean and, although presenting lower initial costs, require more frequent replacement, as the cleaning processes are likely to spoil them. Both the bags that the cartridges can exploit the mechanisms of filtration before described, in dependence on the microscopic shape of the material from which they are made. The materials used are typically polymeric, with treatments and additions which ensure certain performance in specific contexts. A difference that, instead, it is interesting to highlight is the different filtering surface. In fact, frequently the cartridges have a pleated conformation, which allows them to have a much greater filter surface area than conventional bags (compared with a greater risk of clogging).