How Does A Breathalyzer Detect Alcohol From Your Breath? (2023)

Table of Contents (click to expand)
  • Effects Of Alcohol On The Brain
  • Evolution Of Breath Alcohol Analyzers
  • How Is Alcohol Detected?
  • Is Alcohol In The Breath The Same As Alcohol In The Blood?
  • Conclusion

Robert F. Borkenstein’s breathalyzer was a remarkable invention in the field of road safety. It used a simple color-changing chemical reaction to save many lives and keep the roads safer.

Drinking and then getting on the road home wasn’t a major issue during the 1800s. How badly could drunk bicyclists or pedestrians hurt themselves or others while making their way home?

However, Carl Benz introduced the world to the first commercially available automobile in the 1880s, and within a decade, the situation of drinking and driving had turned into a problem.

Then, in the summer of 1954, from the depths of Robert F. Borkenstein’s basement, rose our hero—the Breathalyzer™.

Breath alcohol analyzers are brilliant pieces of equipment that use simple chemistry to save thousands of lives every year. So, let’s get give them their due by getting a bit more acquainted with their origin story and functionality.

But first, we should understand why alcohol makes people menacing drivers in the first place.

How Does A Breathalyzer Detect Alcohol From Your Breath? (1)

DUI accident after drinking and driving (Photo Credit : AntonioKalini/Shutterstock)

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Effects Of Alcohol On The Brain

Driving requires us to multitask, be alert, remain aware of our surroundings, process information, and act with minimal reaction time. To sum up, a driver needs to have complete control over their senses, but alcohol undermines those senses.

Alcohol, instead of getting digested like food, diffuses into the bloodstream through the walls of the stomach and intestines. Once in our body, it goes wherever blood does and gets absorbed anywhere that water is present (since alcohol is highly water-soluble). Thus, all the major organs, including the heart, brain, lungs and muscles, will reach the same concentration of alcohol as that of our blood.

(Video) How Do Breathalyzers Work?

After entering the brain, alcohol enhances the effects of an important inhibitory neurotransmitter, GABA. As a result, our brain cells show delayed response and communication. Alcoholalso dampens the efficiency of the cerebellum, thereby impairing clear vision and motor skills. Read more.

How Does A Breathalyzer Detect Alcohol From Your Breath? (2)

Also Read: How Does Alcohol Change The Brain?

Evolution Of Breath Alcohol Analyzers

In the early 1900s, the only way to detect drunk drivers was to look for the tell-tale signs of drunken driving, such as swerving, excessive speeding, bloodshot eyes, etc. One could also conduct field sobriety tests, which are still in practice today.

However, this system was completely dependent on a cop’s intuition or perception. There were no scientific standards to determine the level of inebriation.

Scientists and authorities eventually came together to find a way to standardize when a person could be charged for “driving under the influence” or DUI.

How Does A Breathalyzer Detect Alcohol From Your Breath? (3)

Roadmap to the invention of the breathalyzer™.

There are many compact and accurate breath alcohol testers available on the market today, but we are going to look at the one that went on to become synonymous with breath alcohol analyzers, the Breathalyzer™. The inventor of the breathalyzer, Robert F. Borkenstein, was a captain at the Indiana state police’s laboratory services, and he later became a professor at Indiana University. He collaborated with Hagner during his work on the Drunkometer and was trained on how to operate it.

This training piqued his interest in breath alcohol analyzers. Since he worked with the police force, he wanted to build something more precise and easier to operate, something that could prove to be a more convenient successor to Hagner’s Drunkometer. After years of trial and error, in the year 1954, he came up with a form for the revolutionary breathalyzer™—the technology that started it all.

Also Read: Why Is Alcohol So Obvious On A Person’s Breath? How To Get Rid Of It?

How Is Alcohol Detected?

The subject (person suspected to be drunk) is asked to blow through a tube into the contraption. They are asked to provide a deep exhale, in order to obtain alveolar or deep lung breath. The operator checks for a deflection in the indicator needle. If the needle moves, it is then brought back to zero with the help of a knob. The demarcation on the knob helps the police ascertain if a person is drunk or not.

How Does A Breathalyzer Detect Alcohol From Your Breath? (4)

(Video) Can you beat a Breathalyzer Test? Breathalyzer Test / Oxidation Reaction!!

Breathalyzer needle indicated BAC (Photo Credit : Raimond Spekking/Wikimedia Commons)

The air from the driver’s lungs enters the test vial, which contains a reddish-orange mixture consisting of potassium dichromate, sulphuric acid, and silver nitrate (catalyst). This mixture, along with the ethanol (the type of alcohol found in alcoholic beverages) from one’s breath, forms a redox reaction system.

In a redox reaction, one of the reactants gets oxidized simultaneously reduces another. The one that is getting oxidized either gains oxygen or attains a higher oxidation state, while the species getting reduced loses oxygen or acquires a lower oxidation state.

The sulphuric acid (H2SO4) in the solution helps in the absorption of ethanol (chemical formula: C2H5OH) from the air into the mixture. Potassium dichromate (K2Cr2O7), loses an oxygen atom upon reacting with the -OH group present in ethanol. Chromium in potassium dichromate has an oxidation of +7, but after getting reduced by ethanol, is at a +3 oxidation state. It further reacts with the sulfate ions (SO42-) from sulphuric acid to form chromium sulfate and potassium sulfate.

How Does A Breathalyzer Detect Alcohol From Your Breath? (5)

The redox reaction that takes place in the test vial.

Ethanol, after gaining an oxygen atom from potassium dichromate, gets oxidized into acetic acid (CH3COOH) and water (H2O). The most fascinating thing about this reaction is that it’s a color-changing reaction. The potassium dichromate solution, which is primarily reddish-orange, in the presence of sulphuric acid and ethanol, gives rise to a green-colored chromium sulfate.

Inside the breathalyzer is a standard vial that has a mixture identical to the test vial, but without any ethanol. There is a light source that illuminates both the vials, and at the other end there is a photocell system that senses the transmittance from both the vials. The difference in transmittance is observed and the quantitative analysis is done according to Beer-Lamberts Law (which states a correlation between the properties of a colored solution and the weakening of light passing through it).

The difference in transmittance of the test and standard vials is dependent on the change in color from reddish-orange to green. The formation of green chromium sulfate depends on the amount of ethanol present in the reaction.

How Does A Breathalyzer Detect Alcohol From Your Breath? (6)

Color of the solution in standard vial vs test vial. (Photo Credit : Ajamal/Shutterstock)

The equipment compares the difference in transmittance and uses the Beer-Lamberts Law to determine the concentration of the green substance, which indirectly indicates the concentration of alcohol in the breath.

Is Alcohol In The Breath The Same As Alcohol In The Blood?

Yes, alcohol in a person’s breath does indicate the presence of alcohol in their blood, but the concentrations are different.

(Video) How long does alcohol stay in your system breathalyzer?

When a person consumes alcohol, it enters the bloodstream and moves through the entire body. During the trip, it gets distributed in the lung tissues and with the air in one’s lungs.

Breath analyzers use an indirect method of calculating blood alcohol concentration (BAC) based on Henry’s Law.

Henry’s Law states that for a closed system at constant temperature and pressure, the concentration of a volatile substance dissolved in a solution is proportional to the concentration of the same substance in the air above the solution.

A human body meticulously regulates its temperature and pressure. Now, if we consider the body as a closed system, then the concentration of alcohol in the air present in a person’s lungs is in proportion to the concentration of alcohol in their blood. Research has shown that the ratio is 2100:1 (i.e., for every 1 ml of alcohol in breath, there is 2100 ml of alcohol in the blood). This ratio is not universal for every human body, but it’s considered an agreeable ratio.

How Does A Breathalyzer Detect Alcohol From Your Breath? (7)

Levels of BAC and its effects on driving. (Photo Credit : gritsalak karalak/Shutterstock)

Drunkenness caused by alcohol varies from one gender to another, and it is also dependent on body weight. All these factors are taken into account while calculating the BAC before charging a person with a DUI. The highest BAC allowed in India is 0.03% (0.03 gms of alcohol per 100 ml of blood), 0.08% in the USA, 0.05% in western Europe. Many countries, such as Hungary, Japan and Iran have a zero-tolerance policy when it comes to drunken driving.

Drunk driving policies and penalties vary from across the globe. To learn more, click here.

Also Read: Why Does Alcohol Affect Women More Than Men?


According to the 2018 Global status report on road safety, produced by the WHO, 1.35 million lives come to an abrupt end due to road accidents every year. And 5-35% of such tragic accidents are related to the influence of alcohol, meaning that ~270,000 people die due to intoxicated drivers. These numbers would be much higher if not for road safety authorities and life-saving breath alcohol detectors.

Never forget how small actions and decisions can have much larger impacts, just like the domino effect of how one molecule loses an atom of oxygen, resulting in thousands of lives being saved across the globe!

References (click to expand)
  1. Win, D. T. (2006). Breath alcohol testers-prevents road accidents. AU Journal of Technology, 10(2), 75-80. -
  2. What Happens to Your Brain When You Drink Alcohol?. Hackensack Meridian Health
  3. How is Alcohol Absorbed into the Body? - Sites@Duke. Duke University
  4. Unit 9: Crime - Breathalyser.
  5. Content: Redox Chemistry Inside the Breathalyzer - Sites@Duke. Duke University
  6. Breathalyzer - The Indiana History Blog -
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(Video) Drink & Drive? How Breathalyzers Work? Blood Alcohol Check?


How does breathalyzer detect alcohol? ›

The alcohol vapor in a person's breath reacts with an orange solution known as potassium dichromate. When alcohol is present, this solution turns green. This color change creates an electrical current, which the breathalyzer can convert into a value to determine the BAC. Generally, the BAC limit in the U.S. is 0.08%.

How much alcohol can a breathalyzer detect? ›

In fact, it eliminates at a constant rate of about . 015% BAC per hour, which is about one drink an hour for the average man. If an average sized man consumed one drink, the maximum BAC on a breathalyzer test would be . 020%.

How long does alcohol stay in your breath for breathalyzer? ›

A breathalyzer can detect alcohol on the breath for up to 24 hours. The amount of time that alcohol stays detectable on the breath depends on the individual and the quantity of alcohol consumed. The detection time varies with a person's metabolism of alcohol, which is affected by many factors, including weight and age.

How does a breathalyzer accurately measure alcohol concentration in blood? ›

Photocells in the breathalyzer measure the degree of color change in the sample containing alcohol and produce an electric current that allows the operator to determine the BAC of the person providing the breath sample.

How does a breathalyzer work chemistry? ›

Breath analyzers (Breathalyzer is a brand name) contain an anode (negatively charged electrode) and a cathode (positively charged electrode). When you blow into a breathalyzer, the ethanol in your breath reacts with water from the air at the anode and is oxidized to form acetic acid (like in vinegar).

What chemical is used to detect alcohol in breath? ›

Silver nitrate catalyzes the reaction in which alcohol, in the presence of sulfuric acid, turns orange potassium dichromate solution green due to conversion of potassium dichromate into chromium sulfate. The intensity of the green color can be used to estimate the amount of alcohol in the exhaled air.

Does drinking water help pass a breathalyzer? ›

Our research shows that manipulations can alter BrAC readings. Specifically, hyperventilation and drinking water before using the breathalyzer were shown to significantly lower the BrAC readings.

Can you have one drink and pass a breathalyzer? ›

Generally, a breathalyzer test can test positive for alcohol for up to 12 hours after consuming one alcoholic drink. The average urine test can also detect alcohol 12-48 hours later.

How do you get rid of alcohol before breathalyzer? ›

These include the following:
  1. Holding your breath. This may concentrate the air breathed out of the lungs and raise a BAC by up to 15%;
  2. Burping. ...
  3. Gum or mints. ...
  4. Using strong mouthwash. ...
  5. Smoking a cigarette. ...
  6. Eating an absorbent material, like cotton. ...
  7. Sucking on pennies. ...
  8. Drinking alcohol without an alcohol smell.
Feb 12, 2021

What is the most accurate way to test for alcohol? ›

Blood Test

While blood testing is more invasive than breath tests and urine tests, it's the most effective at detecting specific alcohol concentration levels. Certain blood tests show the precise levels of intoxication 24 hours after drinking.

How accurate is breath test? ›

All breathalyzers have a margin of error, in some cases as much as 0.01%. That might not sound a lot, but it is critical if you consider that it could be the difference between a conviction and no conviction!

Are breathalyzers accurate enough for to be used as evidence? ›

Are Breathalyzers Admissible in Court? The results of a breathalyzer, or similar breath test, are potentially admissible in court if all the required procedures were followed. But they can also be challenged if there is a reason to believe the results are not accurate.

How long does alcohol stay in blood? ›

The only thing that sobers you up is time. After a big night out you may still be over your legal alcohol limit for much of the next day. After a heavy night of drinking, it can take more than 18 hours for your blood alcohol concentration to get back to zero.

Can you really smell alcohol on breath? ›

There is only one problem with this: Alcohol has no odor. Assuming the officer actually does smell an odor on the breath, what he is smelling is not ethyl alcohol but the flavoring in the beverage. And the flavoring can be deceptive as to the strength or amount consumed.

What's the best way to beat a breathalyzer? ›

You can beat a breathalyzer by hyperventilating, exercising, or holding your breath before you blow. Fact: An often-cited decades-old study found that hyperventilation and vigorous exercise did indeed lower subjects' BAC readings by as much as 10%.

How can I lower my BAC fast? ›

There is nothing a person can do to quickly reduce the blood alcohol concentration (BAC) level in their body. The liver needs time to filter blood and remove the alcohol from the system.
Appearing sober
  1. Coffee. ...
  2. Cold showers. ...
  3. Eating and drinking. ...
  4. Sleep. ...
  5. Exercise. ...
  6. Carbon or charcoal capsules.

Does toothpaste help with breathalyzer? ›

If you've used a product that contains alcohol, the Breathalyzer might detect the alcohol concentration and report a false positive. Products that contain alcohol include toothpaste, aftershave, hand sanitizer, bleach, mouthwash, perfume and cologne. Even spraying bug repellent on yourself can produce a false positive.

How often is a breathalyzer wrong? ›

Generally, breathalyzer tests are only accurate approximately 40% of the time. Factor into that statistic that the testing equipment itself has an inherent margin of error between . 005 and . 02% in its BAC readings.

What can you not eat or drink with a breathalyzer? ›

These can include:
  • Rum cake.
  • Pasta with vodka sauce.
  • Baked goods with a high amount of vanilla extract.
  • Bread, pizza, and pastries that contain yeast.
  • Red wine vinegar (think salad dressing)
  • Soy sauce.
  • Energy drinks.
  • Non-alcoholic beer or wine.

What foods cause false positive breathalyzer? ›

Foods that can trigger false positive BAC results
  • Sugary foods. Cinnamon rolls, honeybuns, protein bars, and pastry.
  • Bread and pastries. Honey-glazed donuts, sandwiches, slices of pizza, croissants,
  • Fruit and juice.
  • White and red wine vinegar. ...
  • Energy drinks. ...
  • Extract.
Feb 7, 2023

What is the least accurate alcohol test? ›

Urine Tests Are the Least Accurate

The amount of alcohol in each person's urine differs significantly based on many factors. The longer it takes to have a urine test completed, the less likely it will be accurate.

What should you not do before a breath test? ›

You must stop eating and drinking 12 hours before the test • Do not chew gum or tobacco 12 hours before the test. Do not smoke 12 hours before the test. Stop taking probiotics for 14 days before the test. This includes any food that contains probiotics.

What is a fail on a breath test? ›

The breath test gives a result straight away. If it shows you're not over the drink-drive limit, you may be allowed to go. If however, you are found to be over the limit, you will be taken to a police station to provide a further breath sample on an intoximeter. If you fail this breath test you will be charged.

What factors affect breathalyzer accuracy? ›

Air and Body Temperatures and Breathalyzer Results

Another outside factor that can significantly alter Breathalyzer test results is temperature, include body temperature and air temperature. Having a fever at the time you undergo a Breathalyzer test can result in inaccurate results, as well.

What could give a false higher alcohol content reading using a breathalyzer? ›

First, breathalyzers do not actually measure a driver's blood alcohol content.
The following foods and medications may cause a false positive breathalyzer result:
  • Nyquil and other cough medications;
  • Sugar-free gum;
  • Kombucha or other fermented beverages;
  • Ripe fruit;
  • Some types of bread; and.
  • Energy drinks.
Apr 4, 2021

Which is more accurate breathalyzer or urine test? ›

Law enforcement will typically use urine analysis when they suspect a person is under the influence of drugs rather than alcohol. Although urine testing is more accurate than a breathalyzer, it's not without error. Urine tests can yield false or skewed results due to both external and internal factors.

Can a breathalyzer detect 1 drink? ›

Breathalyzers can detect alcohol within 15 minutes of your first drink and can continue for as long as the alcohol is in your system.

Will 1 beer show up on a breathalyzer? ›

Is one beer enough to fail breathalyzer? Thus, one 12-ounce can of beer, one 4-ounce glass of wine, or one normal mixed drink or cocktail are all equally intoxicating, and give the same blood alcohol content (BAC) reading on a breathalyzer.

How long does it take for BAC to reach 0 after 1 drink? ›

If a person had only one drink, the maximum intoxication they might have would be about . 02%. Within one hour, their alcohol level would be about zero.

How many drinks does it take to fail a breathalyzer? ›

Standard Drinks and BAC

For every one drink, your BAC goes up by about 0.02 percent, so reaching a BAC of 0.08 percent takes about four to five drinks. However, that does not take into account any of the various factors that contribute to how you process alcohol.

Can you get a false reading on a breathalyzer? ›

Generally, breathalyzer tests are only accurate approximately 40% of the time. Factor into that statistic that the testing equipment itself has an inherent margin of error between . 005 and . 02% in its BAC readings.

Can I drink the night before a breathalyzer? ›

Alcohol could stay in your breath sample for about 24 hours. One standard drink could result in a positive test for up to 24 hours, depending on your burn-off rate. On the other hand, A urine test can detect alcohol in your system up to 12-48 hours later.

How do you sober up fast for a breathalyzer? ›

There's no fast way to sober up once alcohol is in the bloodstream. The only way to sober up is to wait for the alcohol to metabolize. However, the body can only process a limited amount of alcohol per hour. Meaning if someone takes four shots of liquor in a row, those drinks enter their bloodstream one at a time.


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