File into Chest (Quarentine) are safe to stay there. There is no rush to delete anything from the Chest, a protected area where it can do no harm. Anything that you send to the Chest you should leave there for a few weeks. If after that time you have suffered no adverse effects from moving these to the Chest, scan them again (right clicking the file inside the Chest) and if they are still detected as viruses, delete them.
This is a precaution because:
a) system files (necessary to boot and use the computer)
b) false positives (clean files that was wrong detected as being infected) could happen from time to time and it's safer not to delete the file, but send them to Chest for further analysis.