"We rely on the public to educate themselves and indicate if they want to opt out," Melendez said.

At this point, more testimonials from travelers are needed to gain public support for the process, he said.

Maryland resident Anita Khan on Tuesday morning flew into ONT, and said she was not pleased with the scanners. Khan, 26, said she travels at least 10 times a year and does not want to be subjected to the scanners.

"I think it's invasive and a potential harm to our health," she said. "I would opt for a pat-down."

The TSA contends

TSA agent Joann Vallin pulls up an image of a fellow agent's body scan in the screening room during a demonstration on Tuesday at ONT. (Jennifer Cappuccio Maher/Staff Photographer)
the screening is safe for passengers and meets all health standards.

Energy emitted from the millimeter wave technology is significantly less than from a cell phone.

But Khan is not alone. Lawmakers and the American Civil Liberties Union have also opposed the scanners, calling them a "gross violation" of the Fourth Amendment, which guards against unreasonable searches and seizures.

The images could create legal issues if transferred to a server where they could be viewed by more people, ACLU executive director Deborah Jacobs said.

The ACLU reported it has received more than 1,000 complaints in November.

However, the TSA has said the images taken by the machines are not stored and cannot be printed.

The move toward imaging scanners followed the release of the 9/11 Commission Report in 2003. The report found that the TSA was not doing a good job detecting explosive devices, Melendez said.

"We've changed the pat down and installed these machines," he said. "We believe we've done the best to our ability to detect non metallic and metallic threats."

The Associated Press contributed to this report.