Breath alcohol test

Alternative names
Alcohol test - breath

A breath alcohol test roughly quantitates the alcohol content of the blood by measuring the alcohol content of exhaled air.

How the test is performed

The test can be performed after waiting at least 15 minutes since the last drink of an alcoholic beverage (at least 1 minute after smoking).

Breath alcohol testing can be done using either an electronic or manual meter. There are various brands of breath alcohol testers that use different methods to test the level of alcohol in the breath. Carefully read the instructions before using the test to assure accurate testing.

An example of a common tester requires you to inflate the balloon enclosed with the test in one continuous breath until it is full. Attach the balloon mouthpiece to one end of the glass tube. The tube is filled with bands of yellow crystals. Release the air slowly through the tube for 1 minute. Then count the bands in the tube that have changed from yellow to green. If an electronic alcohol meter is used, follow the instructions that come with the meter.

How to prepare for the test
Wait 15 minutes after drinking an alcoholic beverage and 1 minute after smoking before starting the test.

How the test will feel
There is no discomfort.

Why the test is performed
After consuming a drink containing alcohol, the blood-alcohol concentration rises. When the percent of alcohol in the bloodstream reaches .02 to .03%, you may feel a relaxing “high.” When the percentage of alcohol reaches .05 to .10% you have reduced muscular coordination, a longer reaction time, and impaired judgment. Driving is hazardous at these levels. A person with alcohol levels of .08% and above is considered legally drunk in most states (some states have lower levels than others). The alcohol content of exhaled air accurately reflects the alcohol content of the blood.

The test helps you to know how much alcohol it takes to raise the blood-alcohol level to a dangerous level. Each person’s response to alcohol varies. The test may help you make better decisions about driving after drinking.

Normal Values
Normal is when the blood alcohol levels are not elevated, and the bands in the tube stay yellow.

What abnormal results mean
When one band is green, it means that the blood-alcohol levels are between .00% and .05%. Two green bands mean levels of .05% to .10%. Three green bands mean levels between .10% and .15%.

What the risks are
There are no risks.

Special considerations
The test does not take into account the driving abilities of the test subject. Driving abilities vary among people with the same blood-alcohol levels; driving abilities may be impaired in some people with blood-alcohol levels below .05%.

Johns Hopkins patient information

Last revised: December 4, 2012
by Amalia K. Gagarina, M.S., R.D.

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