A 30 day quarantine period is to ensure no one gets each other sick and to get the new chin settled without the added stress. This means separate cages in separate rooms. Please make sure before bringing the new chin into your house that they are of the same sex. If the older chin is a male and your new baby is a female they will try to mate and it would be terrible and detrimental if the baby would get pregnant at such a young age. There is no guarantees, even if you have 2 chins of the same sex, that they will get along after the 30 day quarantine. Please read up on Introductions (in the faq's). Also be prepared for them to be in separate cages if it doesn't work out.
ETA: I just reread your post about sniffing each other. Please do not let that happen within the 30 day quarantine period.