'First off, what is zeroing a hit? Well, for the uninformed, after you hit a pipe, joint, blunt, whatever, rather than exhale, you just let the smoke fester in your alveoli until you can’t stand it anymore and either cough, or just smile and go about your day. I was always under the impression it got you more stoned.'
The Stoner Jesus Show
Mythbusters: Zeroing a Hit Gets You More Stoned
HAILMARYJANE.COM: Mythbusters: Zeroing a hit gets you more stoned