A new Irish study shows it will be challenging for Bluetooth contact tracing apps to reliably detect when people are within two metres of one another.
In a series of tests researchers at Trinity College Dublin found problems with their ability to accurately measure social distancing.
Their study revealed that when people were sitting around a meeting table with phones in their pockets the bluetooth signal strength appeared very low despite them sitting side by side.
Dr Stephen Farrell carried out the research along with Professor Douglas Leith from the School of Computer Science and Statistics of Trinity College.
Professor Leith said the bluetooth signal strength "can vary substantially" depending on how people moved in relation to each other and where people kept the bluetooth device on their person.
He said: “We also found that walls, furniture etc could have a significant effect, especially metal objects such as the shelves and fridges in a supermarket shopping aisle or in a railway carriage or bus."
The professor gave an example of a supermarket trip where the signal strength detected between two people was nearly the same when they walked together or two metres apart.
The HSE's chief executive Paul Reid said it is planning on releasing a contact tracing app at the end of this month.