How Do Breathalysers Work – An Affordable Interlocks Guide

Receiving a court order for an alcohol interlock can feel like a heavy blow. You face a mountain of legal paperwork and confusing technical terms while trying to plan your next move.

Let’s strip away the confusion. In this guide, we’ll break down the science of breathalysers and the Australian interlock rules into plain English. No complex jargon—just the facts.

What Is a Breathalyser?

At its core, a breathalyser is a precision instrument. It captures a simple breath sample to calculate your Blood Alcohol Concentration (BAC) with scientific accuracy.

You likely know them as the tools police use to keep roads safe. Many industries also rely on them to maintain strict workplace safety standards.

For you, however, the device serves a specific purpose. It acts as the heart of your alcohol ignition interlock - the device the court mandates you to install into your car to get your licence back.

The Science Behind Breathalysers

To trust the device, you need to understand your body’s biology. This lies at the heart of explaining how does the simple act of exhaling reveal exactly what is in your bloodstream?

How Alcohol Gets into Your Breath

When you drink, alcohol is absorbed into your blood and circulates through your entire body. Eventually, this blood flows through the lungs to pick up oxygen.

During this process, a tiny amount of alcohol evaporates into the air sacs deep within the lungs. This is known as alveolar air.

When you breathe out, that deep-lung air carries the evaporated alcohol with it. Because there is a fixed scientific ratio between breath and blood, the device can calculate your precise level without a blood test.

Not All Breathalysers Are Created Equal

Did you know that breath testing technology in Australia generally falls into three categories?

At the top end are infrared spectrometry units. These are the large, stationary machines used in police stations to provide definitive evidence for court cases.

The industry standard for mobile testing is the electrochemical fuel cell sensor. This is the highly accurate technology found in police roadside units and all government-approved interlocks.

At the bottom of the pile are semiconductor sensors. You often find these in cheap novelty keychains—they are far less reliable and can easily mistake other substances for alcohol.

Understanding Blood Alcohol Concentration (BAC)

The science is interesting, but your daily reality revolves around a single number - your BAC reading.

What do these figures actually represent? Blood Alcohol Concentration measures the weight of alcohol currently in your system.

It is expressed as grams of alcohol per one hundred milliliters of blood. For example, a BAC of 0.05 means you have 0.05 grams of alcohol for every 100ml of blood in your body.

Knowing the Rules on the Road

In Australia, the legal limits are rigid. For most drivers holding a full licence, the ceiling is 0.05.

However, the law demands a strict zero limit (0.00) for specific drivers. This applies to all Learners and Provisional P-platers.

It also covers professional drivers operating heavy vehicles, public transport like buses or taxis, and those hauling dangerous goods. These rules exist because even a tiny amount of alcohol slows your reaction time and clouds your judgment.

How Accurate Are Breathalysers?

When your driving privileges hang on a digital readout, trust is everything. You need to know the device isn't guessing. This is why every approved alcohol interlock in Australia faces intense scrutiny.

The Official Standard for Accuracy

The gold standard here is Australian Standard AS 3547:2019. This code dictates strict performance and reliability rules for breath testing devices.

To earn certification, a device must survive rigorous independent testing. This ensures your vehicle's interlock meets the exact same accuracy baseline as the handheld units used by police officers during roadside stops.

What About False Readings?

Can something innocent like mouthwash trigger a lockout? The answer is yes - mouthwash does actually contain a significant amount of alcohol and can turn up on an initial test. 

However there are some key safeguards. First, a mandatory waiting period after ignition allows any residual mouth contaminants (debris) to dissipate. However, after this time (around 15 minutes or so) it will still pick-up if your blood alcohol level is high from drinking (not just incidental intake from foods containing alcohol). 

Second, the device demands a long, continuous breath sample. This technique forces the machine to analyse deep-lung air, ensuring the reading reflects your actual blood alcohol level rather than what you just ate or drank.

Legal and Safety Uses in Australia

An alcohol interlock is far more than a standalone breathalyser. It is a complete safety ecosystem designed to physically separate drinking from driving.

How It Connects to Your Vehicle

When a certified technician installs the unit, it integrates directly into your ignition system. Think of it as a gatekeeper for your car's electrical current.

Pass the breath test, and the gate opens—the circuit completes, and the starter motor fires. Fail the test, and the gate remains locked. The engine simply will not crank.

Why the Test Repeats While Driving

A major feature of the program is the rolling re-test. During your journey, the device will randomly prompt you for another breath sample.

This isn't just a trap. It exists to stop a sober person from starting the car for a driver who has been drinking. Don't panic, you have ample time to pull over to a safe location. Crucially, the device will never cut your engine while the vehicle is in motion.

If you miss or fail a re-test, the event is logged in the device's memory. While state rules in NSW, QLD, and VIC vary slightly, this fundamental safety protocol remains the same.

The Role of Affordable Interlocks

Navigating interlock requirements often feels like a maze. At Affordable Interlocks, our job is to clear the path.

As a government-accredited provider, we supply the certified technology you need. We handle the compliance monitoring to satisfy legal obligations, whether you are in NSW, QLD, or the ACT.

We go beyond court orders. We also support businesses with workplace safety solutions and offer personal breathalysers for individual peace of mind. Our promise is simple—respectful guidance to help you meet your obligations with dignity.

Why Breathalysers Matter for Safer Roads

An interlock does more than physically immobilise an engine. Its true power lies in changing behaviour. By demanding a sober breath sample for every trip, the system breaks the link between drinking and driving. The research proves it works.

Evaluations of the NSW Mandatory Alcohol Interlock Program showed a massive drop in repeat offences—up to 86% while the device was active. This builds safer habits that benefit everyone on the road.

We are here to support you through this process. If you are ready to get back on the road, contact Affordable Interlocks today for a same-day quote.