Workplace alcohol breath testing measures the concentration of alcohol in an employee’s exhaled breath to calculate their blood alcohol content (BAC). As alcohol enters the bloodstream, a proportion transfers into the air in the lungs — a breathalyser detects this by generating a small electrical charge when alcohol in the breath passes over an electrochemical sensor. Results are displayed within seconds. Professional workplace breath testing follows a two-stage process: a screening test first, followed by an evidential confirmatory test if a non-negative result is returned. The evidential test uses a mouthpiece to collect a deep-lung breath sample — the most accurate measure of BAC — and produces a legally defensible printed result suitable for disciplinary proceedings and employment tribunals.

Yes. Workplace alcohol breath testing is legal across the UK provided employers follow the correct procedures. This means having a written drug and alcohol policy in place before any testing begins, obtaining informed written consent from the employee being tested, and handling all results in line with UK GDPR. Employers have a legal duty of care under the Health and Safety at Work Act 1974 to ensure staff are fit for duty, and breath testing is a recognised and accepted method of fulfilling that obligation. For certain regulated industries — including rail, aviation and maritime — alcohol testing is a statutory requirement under the Railways and Transport Safety Act 2003. If your business does not yet have a written drug and alcohol policy, this must be in place before testing begins. Contact our team for guidance.

Alcohol is generally detectable on a breathalyser for between 12 and 24 hours after consumption, though this varies depending on factors such as the amount consumed, body weight and individual metabolism. Unlike urine testing, which can detect traces of substances over a longer period, breath testing measures only current alcohol levels in the bloodstream — making it the most appropriate method for assessing real-time fitness for duty rather than past behaviour. It is worth noting that alcohol levels can continue to rise for several hours after the last drink, which is relevant for early morning testing following an evening of drinking. To ensure accurate results, a short nil-by-mouth period of around 10 to 15 minutes is observed before testing takes place.

Outside of specific regulated industries, there is no single statutory workplace alcohol limit in the UK — it is for each employer to define an appropriate threshold within their written drug and alcohol policy. Many employers in safety-critical sectors choose to adopt a low or zero-tolerance approach, commonly set at 0.02% BAC, which is considerably stricter than the England and Wales drink-drive limit of 35µg per 100ml of breath. For organisations operating in rail, aviation or maritime, specific legal limits apply under the Railways and Transport Safety Act 2003. Whatever threshold your business adopts, the important thing is that it is clearly communicated to all employees in advance, applied consistently and embedded within a fair and transparent policy framework. Our team can offer guidance on what is appropriate for your industry and workforce.

Where alcohol breath testing is clearly set out in an employee’s contract or staff handbook, the individual has generally agreed to participate as part of their terms of employment. In cases where no such agreement exists, an employee may decline, and it is important that employers approach any refusal thoughtfully and in line with their written policy rather than treating it as automatically equivalent to a positive result. Getting the policy foundation right from the outset — with clear communication, consistent application and a supportive rather than punitive tone — significantly reduces the likelihood of refusals and helps employees understand that testing is about collective safety rather than individual suspicion. Our team is happy to discuss policy best practice before any programme is put in place.

Employers typically carry out alcohol breath testing in four situations. Pre-employment testing is conducted before a candidate starts work, particularly for safety-critical or regulated roles. Random testing involves selecting employees without prior notice, acting as an ongoing deterrent — best practice recommends testing around 10% of the workforce per month. For-cause testing takes place where there are observable grounds to suspect an employee is impaired, such as slurred speech, the smell of alcohol or erratic behaviour. Post-incident testing is carried out following a workplace accident, near-miss or safety-critical event to establish whether alcohol was a contributing factor. A robust written drug and alcohol policy should define clearly which types of testing your organisation uses, when they apply and what the consequences of a non-negative result will be.