Test Overview

A breath alcohol test is an estimate of your
blood alcohol concentration (BAC). The test measures the amount of alcohol in
the air that you breathe out (exhale).

You can measure your own
breath alcohol level with a simple handheld device. If the device is calibrated
and used according to the manufacturer’s directions, it can provide an accurate
estimate of your blood alcohol level. There are different types of devices available. You can get simple devices meant for home use and professional devices like those used by police for suspected drunk drivers.

Within minutes after you drink alcohol, your blood alcohol
concentration starts to rise. Unlike food, alcohol is absorbed directly through
the walls of the stomach, goes into the bloodstream, and travels throughout
your body and to your brain. This allows blood alcohol levels to increase

The amount of alcohol in your blood reaches its highest
level about 60 minutes after you drink. But food in your stomach may
increase the amount of time it takes for the blood alcohol to reach its highest
level. Most of the alcohol is broken down in the
liver. The rest of it is passed out of your body in
urine and your exhaled breath.

You can buy breath alcohol devices
to measure your BAC at many pharmacies or through the Internet.

  • The manual device is a glass tube (or a balloon
    and a glass tube) containing crystals that change color when exposed to alcohol
    from your breath. This device is less expensive than electronic
  • The electronic meter shows your BAC in a digital
    display window after you blow into a glass mouthpiece attached to the meter.
    This type of meter is more expensive than the manual type.

Many bars and restaurants provide their customers with free
alcohol breath tests using one of these two methods. The devices are also used
to monitor people in an alcohol rehabilitation center or hospital.

Why It Is Done

The breath alcohol self-test is used to
estimate your blood alcohol concentration (BAC). The results can help you
decide whether it is safe to drive. This estimate of blood alcohol is not
intended to represent your actual driving abilities. Your driving may be
impaired even with a low BAC level, such as below 0.05.

The breath
alcohol test offers one piece of information to help you make a safe decision
about drinking and driving. The safest decision is always not to drive if you
have been drinking.

BAC is commonly used by police and other
legal authorities to determine whether a person is legally impaired and should
not drive. A blood alcohol concentration (BAC) 0.08 or greater is
considered legally impaired for adults in the United States. But the legal BAC limit for people under age 18 may be lower, such as 0.02.

How To Prepare

General instructions

  • Check the expiration date on the package.
    Don’t use the test if the expiration date has passed.
  • Store the
    testing device correctly. If the device should be stored in the refrigerator or
    kept in a cool place, make sure you place it in an appropriate storage
  • Follow the instructions exactly. All test kits come with
    detailed instructions. Carefully read the instructions that come with your test
    before using it. Many test kits include a toll-free number you can call for
    more information.
  • Note any special instructions you need to follow
    before you take the test. These might include avoiding certain foods or
  • Follow every step of the instructions carefully.
    • Prepare and handle everything exactly as
      the instructions tell you.
    • Follow all the steps in sequence. Don’t
      skip any steps.
    • If a step in the test needs to be timed, use a
      watch. Don’t guess.
  • Know your limits. If you are
    color-blind or have trouble distinguishing colors,
    have someone else read the test results for you. For some tests, you need to be
    able to see color changes in a test area or window.

Specific instructions

  • Wait at least 15 minutes after having an
    alcoholic drink before testing your BAC. Trace amounts of alcohol left in your
    mouth from a recent drink or the use of mouthwash or mouth spray, such as mouth
    sprays to relieve a sore throat, can give false results.
  • Do not
    smoke for 1 to 5 minutes before testing your BAC. Do not blow smoke into the
  • Take at least two separate readings 15 minutes

How It Is Done

Manual (glass tube/balloon) test

To obtain a
breath alcohol reading:

  • Blow into the balloon that comes with the kit
    until the balloon is almost full. Use one long breath, not several small
  • Attach the balloon mouthpiece to one end of the glass tube
    filled with bands of yellow crystals.
  • Let the air flow slowly out
    of the balloon and through the tube for exactly 1 minute.
  • Count the
    number of bands of colored crystals in the tube that turn from yellow to

If your test has only the glass tube, blow through the
tube for the amount of time in the instructions. Use one long breath, not
several small breaths. Then look at the colored crystals to get the

The amount of alcohol in your breath is based on the
number of bands that change color and on the intensity of the color

Electronic breath alcohol meter

Follow the
specific instructions that come with the device. With most meters, you:

  • Turn on the meter and let it warm up for
    several minutes.
  • Take a deep breath.
  • Place your lips
    tightly around the mouthpiece. Blow steadily and continuously into the machine
    for the correct amount of time (usually 4 to 6 seconds). Use one long breath,
    not several small breaths.

The results appear as a digital readout in a display
window. It may show a red or green “traffic light” or an estimated blood
alcohol concentration (BAC). After you obtain the first reading,
press the reset button and do a second test.

How It Feels

There is no pain from a breath alcohol


There is no chance for problems from taking this
test. You might feel slightly
lightheaded after taking the test.


A breath alcohol test is an estimate of
your blood alcohol concentration (BAC). The test measures the amount of alcohol
in the air that you breathe out (exhale). Results are ready right away.

Manual (glass tube/balloon) test

To read the glass
tube breath alcohol test, count the number of yellow bands of crystals that
turn green.

  • 1 green band roughly corresponds to a BAC of
    0.00 to 0.05.
  • 2 green bands roughly corresponds to a BAC of 0.05 to
  • 3 green bands roughly corresponds to a BAC of 0.10 to

Electronic breath alcohol meter

Some electronic
devices have a “traffic light” display.

  • A green light means a BAC below
  • A yellow light means a BAC between 0.04 and
  • A red light means a BAC above 0.08.

Some devices display the results as an estimated BAC
numerical value.

What Affects the Test

No home test is 100% accurate.
The results may not be helpful if you:

  • Have trace amounts of alcohol left in your
    mouth from an alcoholic drink or even a mouthwash.
  • Smoke. Do not
    smoke for 1 to 5 minutes before doing the test.
  • Have had a drink
    within 30 minutes of performing the test. Your actual blood alcohol level may
    continue to rise after the test.

blood alcohol level depends on:

  • The number of drinks you have and the strength of alcohol (proof or percentage) in the
  • How fast you drink the alcohol. As you increase
    the number of drinks per hour, your blood alcohol level steadily
  • Your
    weight. The more you weigh, the more water is present
    in your body, which dilutes the alcohol and lowers the blood alcohol
  • Your age. One drink raises the blood alcohol level of an
    older adult 20% more than it does for a young adult.
  • How fast your body breaks down
    (metabolizes) the alcohol. Different people metabolize
    alcohol at different rates.
  • Your sex. Women’s bodies typically have less water and more
    fat than men’s bodies. Alcohol does not go into fat cells as well as other
    cells, so women tend to keep more alcohol in their blood than men do. Also, a
    hormones may affect the breakdown of
  • The amount of
    food in your stomach when you drink. Food in the stomach absorbs some of the alcohol. So if you don’t eat before or during drinking, your
    blood alcohol level will be higher.
  • Other medicines or drugs. A person who drinks alcohol and takes certain medicines, such as antihistamines or sedatives (tranquilizers), may feel more of the effects of alcohol. Also, a person who uses other drugs, such as marijuana, will feel the effects of both drugs more than if the drugs were used separately.

What To Think About

A blood alcohol test is more
accurate than a breath alcohol test. To learn more, see the topic
Blood Alcohol.

Driving under the
influence of alcohol (DUI) can be deadly. Alcohol is involved in nearly half of
all fatal highway accidents. Even mild intoxication can impair your ability to
drive safely. At 0.06 BAC, your judgment and physical coordination are
impaired. At a BAC of 0.08, your muscle coordination and driving ability are
significantly impaired.

A person who drinks alcohol and takes
certain medicines, such as
sedatives (tranquilizers), or opioids, may feel more of the
effects of alcohol. Also, a person who uses other drugs, such as marijuana,
will feel the effects of both drugs more than if the drugs were used

Effects of drinking alcohol

Having any amount of
alcohol in the blood can cause poor judgment and slowed reflexes. BAC and the effects of
drinking alcohol vary from person to person and depend upon body weight, the
amount of food eaten while drinking, and each person’s ability to tolerate

Effects of drinking alcohol
Estimated blood alcohol
concentration (BAC)
Observable effects


Relaxation, slight body warmth


Sedation, slowed reaction time


Slurred speech, poor coordination, slowed


Difficulty walking, double vision, nausea,


May pass out, tremors, memory loss, cool
body temperature


Difficulty breathing, coma, possible

0.50 and


You can buy breath alcohol tests on the Internet,
either directly from the manufacturer or from a company that sells this kind of
product. If you have access to the Internet, you can find this information by
searching for the type of test or the name of the manufacturer.


Other Works Consulted

  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.


ByHealthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD – Internal Medicine
Adam Husney, MD – Family Medicine
Martin J. Gabica, MD – Family Medicine
Kathleen Romito, MD – Family Medicine
Specialist Medical Reviewer R. Steven Tharratt, MD, MPVM, FACP, FCCP – Pulmonology, Critical Care Medicine, Medical Toxicology

Current as ofOctober 9, 2017