You learn at a very young age that you should call 911 in an emergency. And, according to the National Emergency Number Association (NENA), people in the U.S. make approximately 240 million 911 calls every year. But not all those calls warrant emergency attention from police, fire department, or paramedics. So what, exactly, constitutes an emergency?

Only call 911 if a person or property is in immediate danger. A serious medical emergency warrants a 911 call, so don't hesitate if you witness a heart attack, stroke, anaphylaxis, broken limbs, choking, drug overdose, drowning, a psychotic episode, or uncontrolled bleeding. If you see smoke or flames, witness a crime being committed, or see a car accident in which someone has serious injuries, call 911. And note that most states are still not equipped to process texts to 911, so stick to using a landline (so the dispatcher has access to your location) or, if you can’t access one, a cell phone.

According to TQ Gaskins, the lead dispatcher at a college police department in Southern California, you should only call 911 to get help for an immediate threat. “If you are at home and hear someone in your house, this is the time to call 911. If you come home and find someone broke into your home while you were away, then you should call the non-emergency line,” she says. “911 lines really need to remain open for people dealing with life-threatening or potentially volatile situations.”

According to Gaskins, most people aren’t aware that every agency has a non-emergency or business line. Go online to your city’s government website to find the non-emergency phone numbers of your local police, fire, and information services, and save them in your phone.

Don’t call 911 to file a noise complaint, report a traffic accident without injuries, or notify the police that your car was stolen. To report a missing person, call your local non-emergency phone number rather than 911, unless the missing person is a child, elderly, or has developmental disabilities. (And it probably goes without saying, but don’t call 911 to ask about weather conditions, parking restrictions, or when your electricity will come back.)

Still not sure if your situation warrants a call to 911? If you’re ever in doubt, err on the side of caution and place the call, then follow the dispatcher’s instructions.