Background radiation is less than 3.5 mSv/year, or less than 0.0004 mSv/hour. So if these tiles radiate 11.37 mSv/hour that would be 28 000 times more than back

Background radiation is less than 3.5 mSv/year, or less than 0.0004 mSv/hour. So if these tiles radiate 11.37 mSv/hour that would be 28 000 times more than background radiation !