According to Edward Hall, intimate distance is maintained when you are:

talking privately to someone

Intimate distance (upto 18 inches) : The distance you maintain when you are talking privately to someone, or interacting with a very close friend or relative.

Personal distance (18 inches to 4 feet) : The distance you maintain when you are interacting one-to-one with a close friend, relative, or even with someone not very close to you in a work setting or other social situation.

• Social distance (4 to 10 feet) : The distance you maintain when the interaction is formal, and not close.

• Public distance (10 feet to infinity) : The distance you maintain in a formal setting, where there is a large number of persons. For example, the distance of an audience from a public speaker, or a teacher in a classroom.