Breathalizer test

OK, so my brother and I were in Brookstone looking for gifts for our mother. We found a Breathalizer test and I used it. I was drinking the night before - up until 3:30am. I got home, went to bed, met my brother at 11am. We were in the Brookstone store at 1pm and I saw a hand held Breathalizer test. So I decided to see how much it could still detect the alcohol from my breath after about 9 hours after I drank. The reading was:

0.05

Technically, it would have been illegal for me to drive a car with that much alcohol in my system...even though it was 9 hours after the fact. Jeez...