How Breathalysers Work: The Science Behind Alcohol Detection

We’re committed to delivering accurate, reliable, and legally compliant alcohol testing solutions. Here’s a straightforward look at how breathalysers work—and the technology behind the tools that support safer workplaces and communities.

What Happens When You Blow Into a Breathalyser?

A breathalyser works by measuring the alcohol in deep lung air, known as alveolar air. This breath sample passes over a sensor that detects ethanol and produces an electrical signal. The strength of this signal determines the amount of alcohol present, and the device calculates and displays the Breath Alcohol Concentration (BrAC).

The Four Stages of Breath Testing

1. Alcohol Absorption

• • Alcohol enters the bloodstream through the stomach and small intestine.
  • As blood circulates through the lungs, alcohol evaporates into the alveolar air.

2. Breathing into the Device

• • The user exhales into the breathalyser.
  • The device captures a sample of deep lung air, which reflects the alcohol concentration in the blood.

3. Detection Methods

• • There are three main types of breathalyser technologies

Australian police primarily use fuel cell breathalysers for roadside screening due to their high accuracy, specificity to ethanol and reliability. For evidential testing (e.g. at police stations), they use infrared spectroscopy devices, which provide legally admissible results.

4. BrAC Calculation

• • The device converts the alcohol level in breath to an estimated BrAC using a standard partition ratio.
  • AS 3547:2019 uses a ratio of 2100:1, meaning 2100 mL of breath contains the same amount of alcohol as 1 mL of blood.

BAC vs BrAC: What’s the Difference?

BAC refers to the amount of alcohol present in a person’s bloodstream, typically expressed as a percentage, while BrAC measures the amount of alcohol in a person’s exhaled breath, usually expressed in grams of alcohol per 210 liters of breath.

Understanding the numbers is one thing – knowing how many drinks is too many makes it practical.

Why AS 3547:1997 Was Replaced

• • The 1997 standard was considered outdated and no longer reflected the capabilities of modern breathalyser technology.
  • Devices had evolved significantly in terms of accuracy, data logging, and sensor technology, necessitating a more robust and current standard.
  • AS 3547:2019 aligns with international and Australian law enforcement standards by using a 2100:1 ratio and expressing results as BrAC.
  • The 2019 standard provides clearer guidelines for workplace and law enforcement use, ensuring consistency in how results are interpreted and reported.
  • It includes stricter performance criteria, such as environmental tolerance (e.g., temperature, humidity), calibration stability, and result repeatability.
  • It brings Australia in line with global standards.

Conversion Formula

To convert BrAC to BAC, the standard formula is BAC = BrAC × 2100. This assumes a 2100:1 partition ratio, though this can vary slightly between individuals due to factors like body temperature and metabolism.

Why Choose an Alcolizer Technology Breathalyser?

At Alcolizer Technology, our devices are built to meet the latest AS 3547:2019 standards, ensuring:

• • High accuracy and reliability
  • Compliance with Australian workplace safety laws
  • Fast, user-friendly operation

Whether you’re managing workplace safety or supporting law enforcement, our breathalysers deliver the performance and trust you need.

Interested in knowing more about Fuel Cell Technology? View our white paper here.