You don't. You design the intake or ducting with inertial separation. The inertia of any debris dense enough to cause damage can't make it to the fan.

In the PT6 turboprop engine, the system forces air to go around a bend, and also opens a trap door. It's actuated by the pilot for landing/takeoff.

https://aviation.stackexchange.com/questions/16206/how-do-in...