Does a stepper motor create a spark?

Stepper motors being brushless will not make sparks. Though brushes are abscent and this totally wipes out the chance of sparking as in other dc motors, being an electrical device, if faults like loose connection occurs, sparks might occur.

How to avoid it? Not quite sure, may be to seal the motor completely and do frequent maintenance to make sure there are no faults. Well, this is a risky condition, need to reconsider it's usage and right safety measures deeper.