When you’re in a public place and some weird string of letters or numbers comes over the loudspeaker, do you wonder what the authorities are really saying? Many organizations use response codes to communicate quickly—or to avoid alerting the public. Airports, police departments, and public transportation hubs all have their own special lingo, and it’s often purposely impenetrable if you’re not an employee.

Of course, we hate missing out on big secrets, so we looked into a few of the most common emergency codes. For instance…

1. Police Department 10 Codes

Decades ago, police departments developed codes beginning with the number 10 to quickly share information with each other. These codes covered most conceivable situations from a 10-44 (riot in progress) to a 10-68 (livestock in roadway). You’re probably the most familiar with 10-4, which means “okay” or “affirmative.”

Unfortunately, the codes were never completely formalized. The Association of Police Communications Officers made the most commonly used list. Still, local jurisdictions had their own idiosyncrasies, and that made communication with other departments and agencies difficult, which is bad news during major catastrophes.

In part due to communication problems during the events of 9/11, the Department of Homeland Security formally recommended that departments replace the 10 codes with plain language. Many state departments, like the Maryland State Police, have followed this advice, but some local departments are sticking with tradition. Considering that a 10-45 can mean there’s an animal carcass, bomb threat, or fist fight depending on which jurisdiction you’re in, that seems like a potentially bad idea.

“Just because something has always been done that way doesn’t mean it’s a good idea now,” says Paul Grattan, a sergeant with a large metropolitan police agency.

“While I haven’t had any incidents that led to confusion personally, the varied systems are ripe for communication issues,” he says. “Take for example three neighboring police jurisdictions: the New York City Police Department, Nassau County Police Department, and Suffolk County Police Department. In the NYPD, a 10-1 would indicate to call your command, though in Nassau—right next door, and often in communication with [New York]— it means that you’re in service. Worse, in neighboring Suffolk County, 10-1 is the highest level of priority indicating an officer needs immediate assistance.”

Still, Grattan says that, while communication is important, plain language probably isn’t the answer to the problem.

“While radio codes are far from top secret, they offer a level of protection against those looking to misuse police communications,” he says. “Some listening in with police scanners know the codes well, but many citizens don’t. … The radio jargon and incorporated codes are a language unto their own, and this benefits police agencies. However, nationwide consistency is a wise idea. There would be a learning curve, but it would be fairly quick.”

2. Operation Bright Star on a Cruise

When you’re chilling on the deck of a cruise liner, the last thing you want to hear is that a fellow passenger is sick or injured. If you hear staff talking about Operation Bright Star, though, that means there’s a medical emergency on board.

This code is usually associated with a lot of running around and looking concerned. Stay out of the crew’s way if you hear it on a cruise ship.

The related “Operation Rising Star” means that a passenger has passed away, according to The Telegraph. However, it’s also the name of a talent show for members of the United States military, so as with many of the other codes on this list, context is key.

3. Codes 1 to 7 on the London Underground

The London subway system is one of the largest and most heavily used in the world. When you’ve got that many people running around in an enclosed space, anything can happen. In most cases, people just make enormous messes.

That’s why Transport for London, the city agency that oversees the Tube, came up with numbered codes to describe a cleaning job to custodial staff. Code 1 means that there’s blood—maybe not on the tracks, but somewhere in the underground station. Code 2 is reserved for “bathroom incidents,” if you catch our drift.

Code 3 warns staff that they’ve got some vomit to clean up (you’d think that “Code 2” would cover that, but apparently not), and Code 4 refers to anything spilled on the floor. Code 5 covers broken glass, Code 6 describes regular old litter, and Code 7 is a stand-in for any other type of cleaning job.

We imagine George Orwell wouldn’t approve the euphemisms for bodily fluids, but commuters trying to scarf their breakfast sandwiches surely appreciate them.

4. The 7000s Aboard an Airplane

Airplanes in flight are the last places you’d want to hear an emergency code, but the flight crew has them (they’re often called squawk codes). If you’re 32,000 feet in the air and you hear the captain warn his crew of a 7600, don’t freak out too badly.

That one just means that the crew has lost communications. They’ll probably be able to get them back up and running soon.

General emergencies are covered under 7700, so it’s hard to recommend the appropriate level of freaking out for that one. It could be cause for full-fledged, Nicolas Cage–level freaking out, or it could simply mean that the plane ran out of pretzels. Actually, the latter could be a big deal. Airline passengers are usually this close to mutiny anyway.

If you hear 7500, though, genuine concern is appropriate. That’s the code airline crews use to convey that someone has successfully hijacked the plane.

5. Speak to Angela at the Club

In 2016, posters began showing up at clubs across the county of Lincolnshire in England.

“Are you on a date that isn’t working out?” one of the posters reads. “Is your Tinder or POF date not who they said they were on their profile? Do you feel like you’re not in a safe situation? Does it all feel a bit weird?”

The posters go on to recommend asking staff about “Angela.” When the staff hear that, they know that you’re in trouble or uncomfortable, and they’ll discreetly call a taxi and sneak you out of the place.

A Hooters restaurant in South Africa developed a similar system and posted it on social media. Their system allows women to ask for more specific aid in code. Asking for an “angel shot” with ice alerts the bartender to call an Uber while asking for an “angel shot” with lime alerts staff to call the police.

These codes are great, but they may not be widely known. That means if you need help, ask the bartender or other staff person in plain English for the assistance you need. Chances are, they’ve dealt with similar situations, and they’ll be more than happy to help get you safely out of a jam.

6. Code Bravo at the Airport

Airports can be unsettling places. There are all kinds of people milling around, the place is super crowded, and all the security makes it seem like something bad is bound to happen at any moment.

That’s why it makes a lot of sense for airport authorities to communicate problems in code. The one to listen for is Code Bravo.

That’s the general security alert that airport staff will use in the event of a threat. They’ll probably also yell, “Freeze!” They figure that legitimate travelers will all obey, and any bad actors will take that cue to run, thereby alerting security staff whom to target.

If you do hear this at an airport, though, it doesn’t mean you’re about to be in the middle of a storm of lead. Usually it’s just a drill. Airport security staff members have to run drills to stay ready to respond to legitimate threats.

7. Code Adam

Another code that airport security staff might use is Code Adam. This one shares the news that a child is missing in the airport. It got its name from the tragic case of Adam Walsh, the late son of America’s Most Wanted host John Walsh.

Code Adam actually extends way beyond the airport, too. Many large retailers have a procedure called a Code Adam plan that will go in place if a parent reports a lost child.

Rich Mellor, a loss prevention expert for the National Retail Federation, told Parents magazine about the Code Adam procedures. Staff will guard all exits, and “during a Code Adam, no child leaves the building without someone from the store questioning the adult and the child,” he said.

While some staff members are guarding the doors, others check through areas like bathrooms and dressing rooms. This can help reunite lost children with their parents and prevent abductions, so it’s a vital program.

8. Walmart Codes

While we’re on the subject of retailers, it’s no surprise that one of the world’s largest has its own set of secret codes used to inform staff of various situations in the store.

If you are ever at Walmart and hear “Code Red” over the loudspeakers, you’ll probably want to head for the nearest exit. That means there’s fire somewhere in the store.

You’ll also want to cut your trip short if you hear “Code Blue” at Walmart. That’s what security uses to spread the news to the store’s staff of a bomb threat. A Redditor shared this photo of a Walmart employee’s badge with the rest of the emergency codes.

The other codes:

Keep in mind that a bomb threat doesn’t necessarily mean that there’s actually a bomb in the store, and security personnel will let you know what to do. Never panic or run.

Still, now that you know Walmart emergency lingo, no one will judge you if you ditch your cart when you hear “Code Blue” come over the loudspeakers. You can feel like you’re some sort of a retail spy.