In safety-sensitive industries such as mining, manufacturing and logistics, alcohol testing is not a tick-box exercise. It is a frontline safety control. Yet one of the most critical factors in alcohol testing accuracy is also one of the most misunderstood: breathalyser calibration. Many South African employers believe that having a calibration certificate on file is enough to demonstrate compliance. In reality, a certificate alone means very little if the calibration behind it was done incorrectly, too infrequently or by an unqualified provider. Getting this wrong can compromise workplace safety, weaken CCMA cases and damage organisational credibility.
What calibration actually means
Calibration is best understood using a simple analogy. A weighing scale placed under a certified 10 kg weight should display a result within a narrow tolerance range. If the scale reads 5 kg, the measurement is clearly unreliable. Even a reading of 9.5 kg falls outside acceptable accuracy limits. Breathalyser calibration follows the same principle. Instead of a physical weight, a certified alcohol reference gas is used.
This gas is manufactured to a known alcohol value, for example 0.35 mg/l. During calibration, the gas is passed through the instrument, and the reading is compared to the known value. If the reading matches, the instrument is considered accurate. If not, internal adjustments must be made, followed by a verification check to confirm alignment.
A proper calibration process includes a pre-calibration assessment, the calibration itself and a post-calibration confirmation. Each step plays a critical role in ensuring measurement integrity.
Why a calibration certificate is not a guarantee
One of the most common misconceptions is that any calibration certificate automatically confirms an instrument’s reliability. This is not always the case. A meaningful calibration certificate should clearly reflect the pre-calibration reading, which indicates how far the instrument had drifted before adjustment. If a device registers 0.22 mg/l against a 0.35 mg/l reference gas, a significant loss of sensitivity has already occurred. A responsible provider would recognise that such a drift indicates an internal fault requiring repair, whereas an irresponsible provider might merely recalibrate the device without addressing the underlying problem. In this instance, the calibration certificate could harm the employer by serving as clear evidence that the instrument is inaccurate. Issuing a long-term calibration certificate is irresponsible, regardless of how professional the certificate appears.
Some service providers issue 12-month calibration certificates for commercial appeal rather than technical justification. While this approach may seem cost-effective, it can leave organisations exposed. In operational environments with frequent testing, many analytical breathalysers do not maintain acceptable accuracy over a full year. Six-month calibration cycles are far more defensible and better aligned with real-world performance data.
How calibration drift puts employers at risk
Calibration drift undermines both safety and compliance. From a safety perspective, an under-reading instrument may allow an impaired employee to enter a high-risk work environment. In sectors involving heavy machinery, vehicles or hazardous processes, the consequences can be severe.
From a labour law standpoint, disciplinary action based on inaccurate readings becomes difficult to defend. In legal proceedings, a calibration certificate can only be relied on once its validity has been proven. The onus rests with the employer to demonstrate that the instrument was accurately calibrated, fit for purpose and traceable to a recognised standard at the time of testing. Certificates that reveal excessive drift or questionable calibration practices weaken the credibility of test results.
Where a calibration certificate is issued by a SANAS-accredited laboratory, that validity is assured, significantly reducing evidentiary risk in CCMA and labour court matters.
What employers should look for on a calibration certificate
A reliable calibration certificate contains more than a date and a signature. It should demonstrate:
- Evidence that the laboratory is properly accredited and technically competent
- Clearly documented pre-calibration and post-calibration values
- The reference gas value used and its traceability
- Environmental conditions such as temperature and barometric pressure at the time of calibration
- A calibration validity period that reflects actual instrument performance, not marketing claims
Understanding these elements is essential for determining whether an instrument is genuinely fit for purpose.
How often breathalysers should be calibrated
There is no one-size-fits-all calibration interval, and blanket claims by suppliers that breathalysers only need annual calibration should be treated with caution.
Breathalysers used to produce exact alcohol readings for disciplinary action require a higher level of accuracy. These analytical instruments should generally be calibrated every six months to ensure their results remain reliable and legally defensible.
Devices used purely for screening and access control work differently. These instruments provide a simple pass or fail result rather than an exact alcohol concentration. In some cases, annual calibration may be acceptable, provided that any positive screening result is followed by a confirmatory test using a properly calibrated analytical breathalyser.
Usage levels also matter. Instruments used frequently throughout the day are more likely to drift out of tolerance and may require shorter calibration cycles. Responsible service providers monitor how instruments perform over time and adjust calibration intervals to ensure ongoing accuracy.
Why reputable calibration providers matter
Calibrating a breathalyser is easy. Proving that it was calibrated correctly is not. Reputable laboratories operate under SANAS-accredited systems, which means their calibration processes, equipment and reference materials are independently assessed and verified. Every calibration is performed under controlled conditions and fully documented.
This ensures that each instrument is calibrated to a recognised national standard and that the results can be relied on if ever challenged. For employers, this removes uncertainty. Alcohol test results issued from SANAS-accredited calibration processes are far more likely to withstand regulatory scrutiny, internal audits and labour disputes.
In a market where low-quality devices and unreliable calibration services are increasingly common, using a properly accredited provider is a practical risk-management decision. When testing for alcohol in the workplace, accuracy is not optional. Proper calibration protects employee rights and gives employers confidence when safety or disciplinary decisions must be defended.
Editorial contacts
ALCO-Safe
Rhys Evans
Managing Director
Tel: 012 343 8114
Email: [email protected]
