From a filter media suppliers webpage:
Wool felts are naturally flame resistant. Although they will burn when exposed to an open flame, when the flame is removed the felt will extinguish itself
Wool felts remain unchanged in physical properties as it wears
Can be hard enough to turn on a lathe and also soft enough to be sewn
Wool felts do not ravel or fray
Highly absorbent and uninjured by continued oil/lubricant saturation
Wool felt is an excellent insulator against cold, heat, sound and vibration.