9-1-1 is only to be used in emergency situations. An emergency is any situation that requires immediate assistance from the police, the fire department, or an ambulance. If you are ever in doubt of whether a situation is an emergency you should call 9-1-1. It's better to be safe and let the 9-1-1 call taker determine if you need emergency assistance.
Do not call 9-1-1:
If you call 9-1-1 by mistake, do not hang up. Tell the person taking the call what happened, so they know there isn't an actual emergency.