The idea emerged after several recent high-rise fires left the family deeply troubled about how residents could safely evacuate.

Speaking to Tuoi Tre (Youth) newspaper on December 15, Nguyen said he and his daughter, Nguyen Ha Hai Nguyen, an 11th grade student at Ly Thuong Kiet High School, dedicated months to developing a practical, affordable solution.

How the system works

Their design integrates a diagonal cable with a controlled descent device that includes an auxiliary brake, a dual shock absorption system made of a spring and a float, a self-adjusting wall anchor that compensates for multi directional drilling angles, and a cable tensioning tool.

Nguyen explained that a person inside the building first secures one end of the cable to a fixed anchor point, then throws the opposite end to the ground along with the shock absorber.

A person on the ground fixes that end in place and installs the spring and float.

The user above then attaches the controlled descent device to the cable, puts on a safety harness, and moves downward along the cable.

When they reach the ground, the shock absorber reduces impact.

Once the first-person lands safely, the cable can be re tensioned if needed, allowing the next person to descend immediately.

This continuous flow, Nguyen noted, helps evacuees avoid hot smoke near the base of the building and lowers the risk of injury.

There are two versions. The dual cable system uses two cables and a lightweight device that weighs just over one kilogram. It is more affordable but slower to install. The single cable system enables quicker setup and evacuation, though the device is heavier at three to six kilograms and more costly.

Nguyen said he conducted real world tests at his home, lowering heavy objects and people from heights up to 12 meters.

"Everything performed reliably, exactly as the calculations predicted," he said. "I find this solution truly effective."

Hoping to contribute to the community

In September 2025, Nguyen filed four patent applications with the Intellectual Property Office of Vietnam, listing Hai Nguyen as a co-inventor.

The filings cover a self adjusting wall anchor, a controlled descent device for diagonal cable escape systems, a ground impact shock absorber, and an evacuation procedure using diagonal cables.

All applications have been accepted as valid in form and are now under substantive review.

If the patent is granted, Nguyen said he intends to waive exclusive rights to the evacuation procedure at his daughter's request, allowing the method to be shared widely.

"My daughter and I hope this solution can reach as many people as possible so it can serve as another viable escape option," he said.

He added that Hai Nguyen played a meaningful role throughout the development. Her questions helped refine the device and the full evacuation process.

Hai Nguyen described herself as an adviser, often raising concerns about potential risks.

"I apply what I have learned in physics about friction and impact, along with my experience from rope swing rides at amusement parks, to suggest ideas," she said.

"I believe losing loved ones takes away much of life's joy. I hope this solution can help reduce suffering in society," she said, explaining her motivation for contributing to the project.