Official guidelines is 3-4 days. We got our own Geiger counter so we could monitor the progress of the half life deterioration. They are only about $100 on Amazon. Out of an abundance of caution and not wanting to inflict "collateral damage" on anyone, and based on the radiation readings, my personal protocol is to isolate for one week, then be cautious about any prolonged contact for a second week. After that, no problem resuming "normal" prostate cancer life.