— Alcohol Concentration Guide

BAC vs BrAC

What Breathalyzers Actually Measure — and Why the Displayed Units Can Look Different

Blood Alcohol Concentration (BAC) and Breath Alcohol Concentration (BrAC) are related concepts, but they are not the same physical measurement. A breathalyzer directly analyzes alcohol in exhaled breath.

Start with the definitions

BAC and BrAC Describe Different Things

They are linked by physiology and by the conversion conventions used in testing systems, but they should not be treated as identical measurements.

BAC

Blood Alcohol Concentration

BAC refers to the concentration of alcohol associated with blood. It is widely used in legal, medical and public-safety discussions, but a breathalyzer does not directly draw or analyze blood.

BRAC

Breath Alcohol Concentration

BrAC refers to the concentration of alcohol in exhaled breath. This is the quantity directly associated with the sample entering a breath alcohol tester.

The key point

What Does a Breathalyzer Directly Measure?

A breathalyzer directly analyzes alcohol in breath. BAC-style values shown on screen are derived display conventions, not a direct blood measurement.

The instrument measures a breath sample, processes the sensor response, and then displays the result in the unit or convention configured for the target market.

Display units

Why Breathalyzer Readings Use Different Units

Alcohol concentration may be displayed in different formats depending on the country, regulation, product configuration and user preference.

mg/L

Breath Concentration

Commonly used to express alcohol concentration in breath.

g/L

Concentration Unit

Used in some markets and device configurations.

%BAC

BAC-Style Display

Often familiar to consumer users in markets that discuss alcohol limits as a percentage.

‰BAC

Per Mille Display

Used in a number of markets where blood alcohol is commonly expressed per mille.

mg/100mL

Blood-Style Unit

Another convention used for alcohol concentration display in certain regions.

The correct unit and conversion behavior should follow the intended market, applicable regulation and the specific device configuration.

Conversion concept

Why Breathalyzer Readings Use Different Units

Breath-to-blood conversion conventions are defined by product design, regulation and jurisdiction. They are useful for standardized reporting, but they should not be interpreted as a direct laboratory measurement of a person’s blood alcohol concentration.

Physiology Varies
Breath-to-blood relationships are not identical in every person or every condition.

Legal Conventions DifferDifferent jurisdictions may use different legal units and conversion approaches.

Device Configuration Matters The instrument should be configured for the target market and intended reporting convention.

Why readings may look different

The Same Alcohol Level Can Be Displayed in Different Ways

Two devices may show different-looking numbers because they are using different units, even when they are describing the same underlying alcohol measurement context.

Different Units

mg/L, %BAC, ‰BAC and other measurement units adopt independent and different numerical scales.

Different Market Settings

Manufacturers may configure the display according to local conventions or customer requirements.

Different Regulatory Context

Legal thresholds and reporting formats vary by country and jurisdiction.

For buyers and OEM projects

Choose Units for the Target Market — Not by Preference Alone

For OEM and private-label projects, the displayed alcohol unit should match the intended market, user expectation and applicable compliance requirements.

Do not assume that a unit commonly used in one country is appropriate for another market.

Physiology Varies

Breath-to-blood relationships are not identical in every person or every condition.

Professional or Consumer Use

Professional programs may require more specific reporting conventions.

Firmware Configuration

Unit selection and conversion behavior should be defined before mass production.

Documentation

User manuals and product labels should use the same measurement terminology as the device.

Airsense product platforms

Multiple Measurement Units Across Airsense Breathalyzers

Airsense product platforms support multiple selectable alcohol concentration units, allowing configurations to be adapted for different markets and applications.