If a burglar breaks into your house, your neighbor keels over in her yard or you witness a major car crash, it’s a no-brainer: you call 911. But in cases of other emergencies, it’s not as obvious when — and when not to — dial those digits.

The general rule: Dial 911 any time there’s a threat to life or property — such as an accident, a crime, a fire or a medical emergency, says Ty Wooten, education director for the National Emergency Number Association, also known as the 911 Association.

A 911 operator can even tell you whether your problem merits a call to 911. So when in doubt, always call. “That’s why we’re here,” Wooten says. “It’s better to be on the safe side.”

Related: Emergency! Should You Drive to the Hospital or Call an Ambulance?

When to call 911

Don’t hesitate to dial 911 if:

1. A fire breaks out. Any fire — even a tiny grease fire in your kitchen — merits a 911 call, Wooten says. A fire can grow and spread rapidly, so call right away even if you think you can put out the flames on your own, he says.

2. A medical emergency happens. Call 911 immediately for any life-threatening medical problem, Wooten says. These include chest pain, choking, difficulty speaking, drowning, numbness, poisoning, sudden intense pain, severe burns, a suicide threat and other serious medical problems, according to the American College of Emergency Physicians.

3. You witness a crime or possible crime. If you see an assault, a burglary or even a suspicious person lurking, call 911, Wooten says. “Go with your gut feeling,” he says. It’s better to call for help now than to have police show up later to ask if you saw anything because they’re investigating a break-in up the street, he says. “If you call, an officer might catch the criminal in the act and foil the crime,” he says.

4. If you’re in or you see a car crash. Call 911, especially if someone is hurt or feels dizzy or unwell. For a fender bender where you’re 100 percent sure everyone is OK, you can call the police directly.

Related: 6 Things Not to Do in an Emergency

When not to call 911

Never call 911 for any situation that’s clearly not an emergency, Wooten says. That seems obvious, but the two 911 centers he ran in Indiana got callers who asked about the weather, current road conditions and even the number for the local pizza joint. Other reasons not to call:

  • A loud party or barking dog
  • A power outage 
  • Burst water pipes 
  • To ask about paying a ticket 
  • You have a cold or flu symptoms
  • Someone has a minor cut 

Many 911 centers operate with only a few dispatchers, so if you call for the wrong reasons, you could delay help for someone with a real emergency, Wooten says.

If you call 911

If you have to call 911, here’s what to do:

  • Know your location. “Where is your emergency?” is the first question dispatchers ask because location is the top piece of information they need to send help. That’s especially important if you’re calling from your cell phone because the dispatcher might not be able to pinpoint exactly where you’re calling from, according to the Federal Communications Commission. If you don’t know where you are, look for buildings, landmarks and street signs.
  • Answer the dispatcher’s questions. Dispatchers ask a lot of questions, but they have important reasons for each one, Wooten says. “It’s not because they’re nosy,” he says. Your answers help the dispatcher determine what kind of help you need, and how much, he says. For example, a dispatcher might send an advanced life support ambulance staffed with a paramedic and special equipment (compared to a basic life support ambulance with EMTs) for a possible heart attack. Or, she might send three squad cars if a suspicious person has a gun, he says.
  • Follow instructions. The dispatcher is trained to help keep you safe and explain how to do first aid while help is on the way. For example, he can instruct you on how to do CPR, walk you through the Heimlich maneuver to help a choking victim or tell you how to stop bleeding. 

Related: 5 Emergency Apps Everyone Should Have On Their Phone

Allie Johnson is an award-winning freelance consumer writer with a degree in magazine journalism. She lives in Georgia with her husband and two dogs.