Why is a fiber filter used in the third filter chamber?

The third filter in new devices, “meaning a dry membrane that has not yet been started”, must be of the fiber type. This is 100% fundamental and is to protect your membrane from the possible passage of carbon particles “even after the black water has been removed from the second filter” and its entry into the not completely wet layers of the membrane. Remember that whenever you try to replace the membrane filter, place the third fiber type filter in its chamber in the same way. It should be noted that when periodically replacing filters, it is okay to use a carbon block filter in the third chamber.