NPCs do not have to pay Zone Chips for upkeep, their Trading Outposts' Safe Zones never expire. Zone Chips are also required as component to build it. The owning faction must power their Safe Zone with Zone Chips. You can configure their force field in several ways, such as allowing neutral grids or faction allies to venture within, allowing or disallowing docking or tool use, up to even outright repelling unwanted players and grids. All NPC Trading Outposts are protected by Safe Zones as well.

Safe Zones can only be activated on station grids, and can only be built for large grids. You can set up a Safe Zone to prevent offline raiding damage when engineers play on a multiplayer server.