When someone’s been drinking and then decides to drive, they may know that they need their blood alcohol concentration (BAC) to go down. They shouldn’t finish off a beer at the local bar and immediately walk out to get behind the wheel. If they wait, their BAC will drop so that they may not fail a breath test, as the legal limit is 0.08%.
But how long do they have to wait? Some people will just spend a half hour checking messages on their phone or drinking a cup of water, and they assume that that’s enough for their BAC to go down. But would there actually be a substantial change?
0.015% per hour is the average rate
The way a person’s body metabolizes alcohol can be a bit different from one person to the next. But as a general rule, researchers note that it is around 0.015% per hour.
As you can tell simply by looking at this number and comparing it to the legal limit noted above, it’s not a very fast rate of decline. It would take a full six hours for a person’s BAC to return to zero if they were just at 0.09%. If they were significantly over the legal limit, it could take them much longer.
As such, a person who spends a half hour drinking water before getting in their car hasn’t really changed their BAC very much at all. If they were over the legal limit, they may not be back under it yet. Plus, their BAC could still be increasing after they finished their last drink, so the decline may not have even begun – let alone dropped far enough to be under the limit.
This can sometimes lead to DUI arrests when people think that they waited an appropriate length of time, but they still have an elevated BAC. If you find yourself in this position, it’s time to look into your defense options.
