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 quickly.
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 meters.
- 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
- 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 area.
- 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 medicines.
- 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.
- 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 device.
- Take at least two separate readings 15 minutes apart.
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 breaths.
- 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 green.
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 reading.
The amount of alcohol in your breath is based on the number of bands that change color and on the intensity of the color change.
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 test.
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 0.10.
- 3 green bands roughly corresponds to a BAC of 0.10 to 0.15.
Electronic breath alcohol meter
Some electronic devices have a "traffic light" display.
- A green light means a BAC below 0.04.
- A yellow light means a BAC between 0.04 and 0.08.
- 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.
Your blood alcohol level depends on:
- The number of drinks you have and the strength of alcohol (proof or percentage) in the drinks.
- How fast you drink the alcohol. As you increase the number of drinks per hour, your blood alcohol level steadily increases.
- Your weight. The more you weigh, the more water is present in your body, which dilutes the alcohol and lowers the blood alcohol level.
- 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 woman's hormones may affect the breakdown of alcohol.
- 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 antihistamines, 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 separately.
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 alcohol.
Estimated blood alcohol concentration (BAC)
Relaxation, slight body warmth
Sedation, slowed reaction time
Slurred speech, poor coordination, slowed thinking
Difficulty walking, double vision, nausea, vomiting
May pass out, tremors, memory loss, cool body temperature
Difficulty breathing, coma, possible death
0.50 and greater
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.
Current as of: March 28, 2019
Author: Healthwise Staff
Medical Review: E. Gregory Thompson, MD - Internal Medicine
Adam Husney, MD - Family Medicine
Martin J. Gabica, MD - Family Medicine
Kathleen Romito, MD - Family Medicine
R. Steven Tharratt, MD, FACP, FCCP - Pulmonology, Critical Care Medicine
Current as of: March 28, 2019