I have questions about PFS

A good rinse and you can put it in, it is selected to be inert, and meant to be backwashed, which helps keep it out of filter machinery. It is also used as filter sand in drinking water purification plants, which should tell something about its condition of use.
When I rinse it, I use my siphon from the tank using old tank water to rinse, and thereby doing a water change at the same time, killing 2 birds with 1 stone,so to speak.