Starting Wednesday, Canadian travellers to the United States could be subject to "heightened screening" of their electronic devices when passing through airport security.

The new measures were announced at the end of June by the U.S. Department of Homeland Security, but offered few details about what exactly the "heightened screening" might entail.

Homeland Security declined to answer specific questions. But a spokesperson for the Canadian Air Transport Security Authority (CATSA), the group that handles security checkpoints at Canadian airports, explained how their officers will carry out those measures.

What's changing?

Not much.

The way it works now, travellers going through airport security might be randomly selected for additional screening, or you might also undergo additional screening if you or your belongings trigger a metal detector or X-ray alarm.

That might mean letting a screening officer physically search through your bag, or swab your belongings for traces of explosive materials.

The difference now, according to CATSA spokesperson Mathieu Larocque, is that travellers might also be randomly selected to remove electronic devices larger than smartphones — think tablets and e-readers — from their carry-on baggage and present them for additional screening, too.

That would involve removing any protective casing around devices to allow for a more thorough physical inspection and proving to officers that the device can be turned on.

"All of the rest of the screening process remains the same," Larocque said. Laptops will still have to be removed from bags and placed in bins individually as before.

Is the data on my device at risk?

No more than usual.

The contents of your devices can still be searched by U.S. border agents, for those attempting to enter the U.S., and by Canadian border officers on your way into Canada. But that would typically be separate from a security screening.

Refusal to unlock your device or give a U.S. border agent your password could deny you entry into the country. And while Canadian border officers can't deny Canadian citizens entry into Canada, refusal to co-operate could result in the seizure of your device.

Security inspectors, on the other hand, are tasked with examining the physical integrity of the device itself — looking for signs that a tablet or laptop has been modified or tampered with, with the intent to cause harm.

"They're not going to be looking at the content of the device," said Larocque. "They're not going to ask you to input your password or look at files. That's not the intent."

What should I expect at the airport?

Larocque says that all travellers — even those flying within Canada — should be prepared to have their devices examined. That means charging devices before arriving at the airport, and ensuring that protective cases can be easily removed, or even better, removed ahead of time.

"Electronic devices that cannot be taken out of their cases or powered on when requested during enhanced screening will not be permitted beyond the screening checkpoint," according to CATSA's site.

If all this sounds familiar, it's because there was a time when screening officers could ask travellers to power on devices such as laptops, but Larocque said the practice was discontinued for several years — until now.

And don't forget that airlines are advising travellers to get to the airport two hours before their scheduled flight to the U.S., to allow time for the screening.

Here's what border agents can search for on your phone (and more):