in most circles it's only applied to Blunts or Joints and is classified (at least, by me) as two full exhales. However, when smoking with only a few (1 or 2) close friends, it is mainly overridden and you are allowed to 'hold on to it' for a decent amount of time (avg 1 minute to 1 minute and 30 seconds) but no more than 2 minutes, unless it's a fat blunt. The puff-puff-pass rule is chiefly applied at parties with a lot of people smoking, and only one or two joints/blunts being passed around to many people. remember, everyone else wants to smoke too! don't hold it for too long if you're in a large group!!!