Call 911 whenever a situation requires immediate assistance from police officers, fire fighters or emergency medical personnel, explains 911.gov. Some examples of such situations include crimes, fires, car wrecks, difficulty breathing, injuries resulting in uncontrollable bleeding, chest pain and severe allergic reactions.
When unsure if a situation warrants dialing 911, proceed with the call, and allow the person who answers to determine if sending emergency assistance is appropriate, recommends the National Emergency Number Association. If the situation is not severe enough to send immediate help, the call taker can advise the caller on how to handle the situation instead.
It is illegal in most states to prank call 911 or call with the intent to harass the call taker, warns the National Emergency Number Association. The Association advises that people make sure everyone living in their home is aware that doing so can lead to legal consequences.
Try to remain as calm as possible when calling 911 while providing the call taker with the information necessary to dispatch assistance to the site of the emergency. Be ready to provide the phone number used to call and the location and nature of the emergency, explains 911.gov. In some cases, the call taker provides instructions to take until help arrives, such as to perform CPR or unlock the front door.