Why must empty radioactive packages that previously contained Class 7 goods be inspected and monitored before being returned as UN 2908 (Excepted Package - Empty Packaging)?

1. To check whether the box can be used for packing groceries
2. To verify that internal and external non-fixed contamination levels are below excepted package limits and surface dose rate is under 0.005 mSv/h
3. To make sure no water is inside
4. To paint the outside box red