SWEATY armpits had alarm bells ringing at Sydney Airport yesterday with controversial full-body scanners baulking at perspiring passengers.

The second person to use the new machine, part of a $6 million trial, triggered the alarm three times. Security staff blamed the passenger's armpits for upsetting the machine.

From today travellers will be able to volunteer to trial the scanner, which uses low-energy radio waves to detect items concealed under clothing, as the federal government assesses how best to roll out the new technology at major airports.

Transport Minister Anthony Albanese pitched the scanners as the "most advanced passenger screening technology available in the world".

However the device, which uses advanced computer software to detect miniscule differences in the radio wave radiation that is reflected from the body, has come under fire in Europe for being slow, inaccurate and ineffective.

Last week German police rejected the scanners for being too sensitive, saying in more than two thirds of cases the alarm had gone off in error, with the machine confused by multiple layers of clothing, zippers, and even a passenger's posture.

Mr Albanese said the trial aimed to simply highlight the position of suspicious objects on an empty outline of a person.

"There were, I believe, some legitimate concerns about privacy that had been raised," he said. "We know unfortunately that we live in an unsafe world, and in those circumstances this government will ensure that people's security is looked after."

Mr Albanese also said the cost of any broader roll-out of the machines would be borne by private airport operators, although a final decision would not be made until after a similar trial next month in Melbourne.