1. Recently visited or passed through areas with high epidemic risk, and stayed for more than 4 hours. My health code may turn yellow at that time. 2. If I stay in the same space-time grid with the confirmed patient for * * * more than 10 minute within 14 days (usually 800 meters *800 meters as the detection range), then I will be judged as a space-time companion at this time, and the health code will also be included in the yellow code range.