In a recent study of Finnish drivers who owned breathalyzers, a large majority used their breath testers the next day or morning out of concern that their BAC had not yet fallen below the legal limit (Drinking and Driving Safely: Who uses Breathalyzers and When).
This may seem surprising until one realizes that it can take up to one hour for the body to rid itself of the alcohol in just one standard drink. A night of heavy drinking can easily find you in the morning with a BAC over the legal limit. This level of impairment combined with a lack of sleep makes for a deadly combination on the road and possibly at work.
Never hit the road the morning after a night of partying if you are unsure about your BAC level.
I use my LifeGuard for family and personal use especially the morning after a celebration (i.e. a wedding) to see that I and others are safe to drive. Since the stakes are high it is essential that I can rely on my breathalyzer. I have used the cheaper silicon oxide breath testers and found them unreliable and inconsistent. LifeGuard gives very consistent and accurate results and could not be easier to use. From my personal experience I highly recommend it.
-JR Bingham, United Kingdom