Abstract: A blood-alcohol content (BAC) tester for use at a facility serving alcohol. The BAC tester includes a breath-sampling unit having an air-chamber unit defining a closed position and an open position. The air-chamber unit has a first air-chamber block and a second air-chamber block, the first air-chamber block and the second air-chamber block defining an air chamber for receiving air exhaled from a user. The breath-sampling unit also includes a drive unit coupled to the second air-chamber block and an alcohol sensor. The BAC tester also includes a sensor circuit communicatively coupled to the drive unit and the alcohol sensor. The sensor circuit is configured to cause the drive unit to move the second-air chamber block relative to the first air-chamber block so as to cause the air-chamber unit to be in the closed or the open position.