Final answer:
The legal BAC limit for drivers 21 and older is 0.08%. The Breathalyzer is used to measure BAC, and alcohol is metabolized by the liver at a rate of about 15 mg/dL per hour.
Step-by-step explanation:
The legal blood alcohol concentration (BAC) limit for a driver ages 21 and older in most US states is 0.08%. This limit is set to prevent driving under the influence of alcohol, which impairs motor skills and judgment, making driving unsafe. When BAC reaches higher levels, such as 0.20%, it can cause acute intoxication, and levels around 0.30% can lead to unconsciousness. A BAC of about 0.50% may even result in death.
The Breathalyzer device measures the ethanol concentration in a person's breath, which correlates with their BAC. It's important to keep in mind that alcohol metabolism rates vary, and the liver breaks down alcohol at a rate of approximately 15 mg/dL per hour. Therefore, planning enough time for the body to metabolize alcohol before driving is crucial to staying within legal limits and ensuring safety.