CHICAGO (CBS) — The moment the World Trade Center towers were hit by hijacked passenger jets on Sept. 11, 2001, a wave of fear went through people living and working in skyscrapers across the United States.

The question: Could it happen here?

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CBS 2’s Audrina Bigos reports on how high-rise security has tightened since then.

To better prepare for future attacks, security consultants like Lauris Freidenfelds analyzed the security and emergency response on 9-11.

“We learned that there were some superhero security directors and emergency managers,” Freidenfelds said. “Their people knew how to get out of the building in a safe and quick manner because they drilled and exercised before that.”

Freidenfelds spent most of the last decade running security and emergency management at Rush University Medical Center and now works at Telgian, which develops fire emergency and life safety systems and anti-terrorism solutions.

One of the most important changes in the past 20 years?

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“Public law enforcement and private security need to share resources,” Freidenfelds said.

Chicago now requires high-rises to have an emergency evacuation plan on file with the city. And the tallest buildings must give the fire department their floor plans, so emergency responders know what they’re walking into.

“So we can know who’s the engineer, who’s in charge of security, if there are layouts that are associated with your building, you can upload it into our system,” said Rich Guidice, executive director of the city Office of Emergency Management and Communications (OEMC) said.

After 911, OEMC because Chicago’s liaison with the U.S. Department of Homeland Security, tasked with protecting the nation from threats.

William Sako, vice president of security risk consulting at Telgian, specializes in security risks.

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“The better the police and fire who are responding to a problem in the building can understand the condition of that environment,” Sako said, “the better that they’re aware of what’s going on, the better than can be prepared to save lives when they enter the facility.”