Why no shoes? TSA demystifies airport security

It's no fun enduring the barefoot walk of shame as unsmiling TSA officers eye the underwear in your backpack while a leaky 3.4-ounce container of shampoo soaks your passport.

We get that, Transportation Security Administration officials said Friday at O'Hare International Airport. But protocols are in place for a good reason, they emphasized during a demonstration intended to explain why they do what they do.

“This looks like an ordinary laptop,” TSA spokesman Michael McCarthy said, gesturing at a computer and sounding like a magician. “But it's been altered. When you lift it up you can see there's a mock explosive placed inside.”

That makes sense. But why must shoes come off?

“These look like everyday shoes, but they feel a little bit heavier,” McCarthy said, indicating a pair of sneakers. “That's because if you peel back the tongue there's a mock explosive inside there and here's the ignition.”

The shoe explosive was similar to one unsuccessfully detonated by Richard Reid in December 2001 on an American Airlines flight from Paris to Miami.

TSA screenings are “based on real-life events that occur or when intelligence tells us we should look for those items,” McCarthy said.

On a recent trip, my 3.4-ounce container of shampoo leaked all over and my water bottle was confiscated by the TSA.

But I can't complain after McCarthy showed off a doctored soda can hollowed out at the bottom to fit a blasting cap, a small explosive device that triggers a more powerful one.

Why 3.4 ounces as the limit for liquids in carry-ons?

TSA experts have concluded that “something less than 3.4 ounces likely wouldn't cause catastrophic harm,” McCarthy said.

Here are a few more eye-openers:

It's understandable why children younger than 12 are exempt from removing their shoes, but what about those 75 and older?

The TSA has moved to a “more risk-based approach to screening,” McCarthy said. “Our intelligence tells us passengers 75 and older could be a lower-risk population.”

The government offers a PreCheck program where people can apply for a trusted traveler number that expedites screenings. That status expires after five years. Why five years?

McCarthy didn't give away trade secrets, but said experts had decided five years was the limit someone can be defined as a known traveler. Also, names on PreCheck are “continuously vetted against terror watch lists.”

You may have been at an airport and waved into a PreCheck line without having those credentials or been allowed to keep your shoes on. What gives?

The answer could lie in that friendly TSA dog you brushed past that knows the faintest scent of chemicals, McCarthy said.

“Their noses are refined tens of thousands of times compared to human ones. If the dog doesn't detect anything, you can be moved to the PreCheck line.”

Another reason could be a “risk-based analysis based on your name, date of birth, gender, the cities you're flying to.”

And the one you've all asked: Why can't I bring my inert grenade to the World War I re-enactors convention?

“Even a replica of a grenade is not allowed in carry-on or checked luggage,” McCarthy explained. “An item like this can cause quite a panic at an airport.”

Got a TSA question or story? Drop me an email at Or check out

<h3 class="leadin">One more thing

“What's the weirdest item you've intercepted?” we asked TSA Lead Officer Craig Vargas.

There was the time months ago when an “organic mass” showed up inside a DVD player in a carry-on. Turned out the organics were baby turtles concealed in a man's carry-on.

“He got the short end of the stick,” Vargas said. “He thought he was smuggling expensive turtles and they were just $5 turtles.”

The turtles were not detonated. Instead, U.S. Fish and Wildlife picked them up.

<h3 class="leadin">You should know

Chicago's overnight runway rotation test at O'Hare continues with a new lineup this week that will affect folks northwest and southwest of the airport if everything stays on schedule. If something changes, the city will shift to a Plan B that impacts people in Des Plaines and southwest of the airport.

<h3 class="leadin">Gridlock alert

Sorry Bloomingdale, IDOT will close one lane of eastbound Lake Street between Prairie Avenue and Glen Ellyn Road Tuesday and Wednesday from 6 a.m. to 6 p.m. for pavement repairs.

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