More than four million people have already downloaded the Australian government’s COVIDSafe app, but there are concerns about the accuracy of its tracing capabilities.

Prime Minister Scott Morrison has urged millions more Australians to download the app, in order to facilitate the easing of social distancing restrictions, but a signalling expert has warned there will be many false positives as app uptake increases.

Biomedical signal expert from RMIT University, Professor Dinesh Kumar, said the accuracy of results in high density areas is likely to be a problem.

“Bluetooth, which is the technology behind this app, goes through walls and through glass, and things like that, and the ceiling,” he told 3AW’s Neil Mitchell.

“What that means is people who are in different rooms, or different shops, or different offices, or different apartments, could be considered to be together.”

At one student apartment complex in central Melbourne, Professor Kumar said it was possible for one person to register as a connection with more than a dozen others while they were in separate residences.

“You can have 16 apartments at one time giving connection with one person who may have the disease,” he said of the student accommodation.

But Professor Kumar urged Australians to download the app.

“We should not discount the app, he said.

“We need such a thing because it will help people, however … there are certain limitations which we should be aware of so we don’t freak out because there are so many false positives that may come,” he said.

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