A friend just dissolved a whole 8mg sub a few min ago. Says he takes percs n shit all the time but idk bout tolerance. Wats the chance of od or resp failure?
We're not going to be able to tell you for certain without knowing the exact(ish) amount of "Percs n shit" that your friend takes.
As long as they've not taken any other CNS depressants such as Benzos or Ethanol then they're likely to be ok seeing as they're likely to have atleast a bit of a tolerance.
I must stress though that we can't be sure. Make sure that someone is keeping an eye on them at all times and if there's any symptoms of OD then get them to a hospital ASAP.