they remove virtually all O2.https://en.wikipedia.org/wiki/Oxygen_scavenger#Mechanism wrote:Absorber technology of this type may reduce the oxygen level in the surrounding atmosphere to below 0.01%.
you can't pull a super hard vacuum when packaging tea. even with ball-rolled teas, there is still some air left in the bag because of void space between the balls on the interior. it works best on something like an individually sealed meat stick snack or strip of jerky where the packaging can make full contact with the contents (no free interior volume).
the thing that's nice about vacuum sealing though is it's visually obvious when the bag is damaged.