Elevator safety is moving up.

Thyssenkrupp Elevator has installed the first Occupation Evacuation Operation in a U.S. high-rise building.

The lifts are in the 800-foot 181 Fremont building in San Francisco, which has worked hard to distance itself from the sinking Millennium Tower by ensuring engineering was stable enough to survive an earthquake.

Now, the developers are focusing on internal building safety as well. More than 80% of the elevators installed in the tower are designed to continue operating even during emergencies, meaning occupants can escape quickly in the case of a disaster or attack.

The design was based on findings from a study conducted by the National Institute of Standards and Technology, which looked at building evacuation processes following the 9/11 attacks. The new design combines the use of stairwells and elevators while also providing accommodation for those with restricted mobility.

“The number of high-rise buildings has tripled since 2000 as more and more people gravitate toward living or working in cities," thyssenkrupp CEO Rich Hussey said in a release. "The implementation of OEO enabled elevators in U.S. high-rise buildings is a critically important step toward ensuring people’s safety in the event of an emergency, and it’s only the beginning. In the near future, hopefully many of the high-rise buildings being designed in major markets will incorporate OEO functionality for their elevators."

The elevators are also built to protect against elements like water, heat and smoke and can run on backup power in the case of a power outage.