You need to have your new snake in as close to a seperate airspace as possible. Ideally, it would be in an entirely different location than where your snakes are currently, but this is not always possible for everybody. We keep our collection in a closed room on one end of the house, and the quarantined animals go in a seperate room on the other side of the house - with no central air going in the summer, and in the winter the 'snake room' doesn't have any vents, resulting in minimal air transfer. We don't handle or interact with the quarantined animals unless absolutely necessary, and if we do, they are the last to be touched, and we don't go into the snake room afterwards unless a clothes change and thorough scrub-down or shower beforehand. The recommended time for quarantine varies for each person, but we like to do a minimum of 3 months, and try to only take in animals from trusted sources.