Static charge buildup In case of air coming from a fan, can the it develop static charge due to its rubbing with the frame material?(and also, there a way to ionize air without a spark?)
 A: The Air from the fan has developed some charges but the magnitude of charge is so small, that we don't consider it usually.
And there is no certain thing spark, the high voltage difference creates spark and ionizes the air around it.
See, air consist of many molecules and atoms of different elements so ionizing them basically means aligning those atoms or molecules in a certain direction creating voltage difference.
Hope you get my explanation.
Ps: I've answered on stack exchange for the first time.
A: 
In case of air coming from a fan, can the it develop static charge due
  to its rubbing with the frame material?

From what I know, an air flow can charge objects if it carries some particles, like dust, sand or droplets of liquid. Otherwise, at least for relatively low velocities like you expect from a fan, there should be no significant charging.

Is there a way to ionize air without a spark?

The simplest way to ionize air without a spark is just to rub a balloon against wool - the air around balloon will be ionized for at least several minutes.
If you need a greater duration and control, you can apply high voltage, on the order of several kilovolts (any Van de Graaff generator should do), to a sharp metal object, like a needle - the air around the tip will be ionized. There should be no grounded metal object too close to it - otherwise you might get a spark or an arc.
