I dont know about the limit percentage, but a cdl holder will be in more trouble even if off duty and in a car. The fine is higher and the license revokation time period is longer. I believe it may also be revoked on the first offense for the maximum period of time, but since I dont drink, I can only go by what too many of my friends that cant drive because their license is revoked, say. Kind of like an EMT. Even if you are not on duty, if you come upon an accident say, it is your responcibility to stop and administer aid. If you are caught not stopping, you will be in trouble.