BAC vs BrAC: What is the Difference?

BAC stands for Blood Alcohol Concentration and BrAC for Breath Alcohol Concentration. BAC results are obtained by taking a blood sample, while BrAC results are obtained by taking a breath sample. So how does it work if law enforcement officers use field breathalyzers to test your BrAC but display the results in BAC? Simply put, there is a chemical correlation between the alcohol content in your blood (BAC) and your breath alcohol content. BrAC results are converted to blood alcohol concentration (BAC) – we’ll explain how below.

For example, OCIGO will accurately and reliably measure the BrAC in your breath sample and display the BAC results on the device (not available in France) and on the app. It’s worth noting that BAC result displays differ across European countries due to varying legal limits.

To better explain the difference between BAC and BrAC, we first need to understand the physiology of how alcohol is processed by our bodies once it has been ingested.

Electronic Breathalyzer to Know Your BAC/BrAC

OCIGO is an electronic and connected breathalyzer that measures your blood and breath alcohol levels. Thanks to its connected mode, you can perform an alcohol test and see the data directly on your phone! It uses the same technology as law enforcement tools, making it ultra-reliable and accurate.

How Does Alcohol Get Into Your Bloodstream?

When you drink alcohol, it goes through your mouth, down your throat, and into your stomach. However, it’s neither digested nor chemically processed in your stomach. Instead, it escapes from the stomach and/or small intestine into your bloodstream through a process called diffusion. In other words, alcohol is absorbed through the cell membranes of your stomach and small intestine and goes directly into your blood. This passive process happens automatically. This is why you get intoxicated faster when drinking on an empty stomach. Eating food helps slow down this process.

How Does Alcohol Get Into Your Breath?

Once the alcohol is in your bloodstream, it is carried throughout your body via the venous system and the pumping of your heart. This includes your lungs, where some of the alcohol present in your bloodstream remains as the blood passes through and the oxygen and carbon dioxide exchange occurs. Every time you inhale and exhale, the remaining alcohol in your lungs passes back up through your throat, into your mouth, and out.

Relationship Between BAC and BrAC

The relationship between BAC and BrAC is determined by the Blood/Breath Ratio (BBR). The concentration of alcohol in breath is about 2,000 times less than in an equal volume of blood. To compare BAC and BrAC, you need to multiply the concentration in breath by a factor, the blood-breath ratio (BBR).

$\text{BAC}=\text{BrAC}\times \text{BBR}$

This BBR of alcohol was originally thought to be 2,100:1 when the Breathalyzer was approved for use in the USA and Canada to estimate the BAC (Borkenstein and Smith, 1961). However, scientific studies involving controlled drinking experiments or tests with apprehended drivers show that in most of the studied population, the ratios can vary between 2,000:1 and 3,000:1.

Understanding Alcohol Units

In Europe, BAC is measured as follows:

• Latin countries: g/L
• Anglo-Saxon countries: mg/100mL
• German and Scandinavian countries: ‰[w/w] or g/kg

For BrAC, the standard metric in Europe is mg/L, except for Anglo-Saxon countries, where it is µg/100mL.

To easily convert BAC to BrAC, you can divide the BAC result by 2,000 to obtain your approximate BrAC result. In other words, if your BAC is 0.8, your BrAC would be around 0.4.

Conversion Ratios Used in Different Countries

Currently, countries do not agree on a standard BBR, and unfortunately, there isn’t a single scientific formula to determine the exact ratio. In Europe, the BBR can vary between 2,000:1 and 2,292:1.

Breathalyzers like OCIGO allow you to measure your alcohol level, and the OCIGO app helps you to easily adapt BAC and BrAC levels among European countries.

If you want to convert your BAC to BrAC or vice versa, use our alcohol unit converter. It considers the BBR of each country and provides a very accurate conversion!