Whether you're managing site safety, overseeing a transport depot, or conducting random staff screenings, one question often comes up:
How long can alcohol be detected using a breathalyser?
The answer isn't always straightforward.
Detection times depend on several factors, including the amount of alcohol consumed, how recently it was consumed, and the type of breathalyser being used.
This article takes a look at the science behind detection, typical timeframes, and what businesses should consider when planning routine alcohol testing.
So What Does A Breathalyser Actually Detect?
A breathalyser does not measure alcohol in the bloodstream directly. Instead, it captures a sample of exhaled air and measures the alcohol content.
This is then used to estimate Blood Alcohol Concentration (BAC), which is the standard measure used in both legal and workplace contexts.
Devices, such as the Dräger Alcotest® 6000 or the Intoximeter Alco-Sensor FST, use electrochemical sensors (fuel cell technology) for this process.
These sensors are reliable, consistent, and suitable for professional use across industries.
How Long Does Alcohol Stay On Your Breath?
On average alcohol remains on your breath for up to 12 hours after drinking. However, this window can vary significantly depending on:
How much alcohol was consumed
The individual’s weight and metabolism
Whether food was eaten at the same time
The type of alcohol (beer, wine, or spirits)
Time since the last drink
In some cases, small amounts of alcohol may be picked up even after 24 hours, especially with sensitive equipment or when high volumes have been consumed.
Can You Still Test Positive The Next Day?
Yes, and it’s more common than people realise.
Staff who drink heavily in the evening may still show a positive result the next morning. This is particularly relevant in industries with early starts and strict safety requirements.
For example, if someone consumes eight units of alcohol (around three pints of strong lager or four large glasses of wine), their BAC may remain above your workplace threshold until mid-morning or even later in some cases.
Many businesses now treat morning testing as a priority, not only to meet legal obligations but to protect staff and workplace safety.
Is One Drink Enough To Test Positive?
It can be.
Even a single unit of alcohol may be detected if tested shortly after consumption. Some workplace policies have zero-tolerance approach, meaning any alcohol level above 0.00% could result in a failed test.
This is especially relevant in safety critical environments where even a mild impairment can lead to incidents or errors.
In these cases, communication and training are just as important as testing itself.
Professional breath alcohol testers are sensitive enough to detect small traces of alcohol, so it’s essential that employees understand what the policy allows, what is considered to be over the limit, and how long alcohol can remain in their system.
How Reliable Are Workplace Breathalysers?
Professional devices are designed for accuracy and fast results and are used by police forces, emergency services, and commercial operators alike.
Key factors that ensure accuracy include:
Regular calibration (usually every 6 to 12 months)
Use of sealed, hygienic mouthpieces
Proper training in test procedures
Appropriate use in line with manufacturer instructions
When maintained and used correctly, these devices give results accurate to within ±0.01% BAC, even in varied conditions.
What Does This Mean For Your Workplace?
Understanding alcohol detection times helps shape practical, enforceable safety policies, making sure staff know what is expected of them and gives employers confidence in their testing process.
Whether you’re running random spot checks or post incident investigations, having a reliable alcohol testing kit on hand supports a safer working environment and compliance with industry standards.
It also demonstrates a commitment to health and safety that can strengthen your company’s reputation and employee trust.
Breath alcohol detection isn’t just about catching someone over the limit.
It’s about making sure your team is fit to work and your business meets its duty of care.
Alcohol can remain in the system longer than many people realise. With the right alcohol tester, and trained operators, you can test with consistency, accuracy, and confidence, day in, day out.