Sulphur Dioxide Monitoring

What is sulphur dioxide monitoring?

Sulphur dioxide monitoring measures the airborne concentration of sulphur dioxide gas from fuel combustion, smelting and food preservation that workers may breathe in during normal operations. It quantifies real personal exposure so employers can judge whether existing controls are adequate.

IndustrialAirMonitoring.uk provides independent sulphur dioxide monitoring across smelting and metals, power and combustion, food and beverage, chemical sites throughout the UK. Our occupational hygienists deliver defensible exposure data that demonstrates compliance with the Control of Substances Hazardous to Health Regulations 2002 (COSHH) and the workplace exposure limits set out in HSE guidance note EH40.

Why sulphur dioxide monitoring matters

Under COSHH Regulation 10, employers must monitor exposure to hazardous substances where it is needed to protect health, where a workplace exposure limit could be exceeded, or where control measures need to be verified. Sulphur dioxide monitoring provides the objective evidence that satisfies this duty.

Uncontrolled exposure to sulphur dioxide is linked to bronchoconstriction, respiratory irritation and aggravation of asthma. Beyond the legal duty, robust monitoring protects your workforce, reduces the risk of enforcement action and civil claims, and gives insurers and clients confidence that exposure is being actively managed.

How we carry out sulphur dioxide monitoring

We measure exposure using direct-reading electrochemical detection and sorbent sampling for time-weighted assessment, following the recognised EH40 / direct-reading methodology. Personal samplers are worn in the breathing zone for a representative full shift to derive an 8-hour time-weighted average, while static (background) samples help map contaminant sources across the workplace.

Samples are analysed by an accredited laboratory and the results compared with the relevant occupational exposure limit. Where short-term peaks are a concern we add 15-minute short-term exposure limit (STEL) sampling, so both the chronic and acute risk picture is captured.

Standards, limits and reporting

The current workplace exposure limit for sulphur dioxide is 0.1 ppm (15-minute STEL) (EH40/2005, as amended). We assess compliance using the BS EN 689 statistical decision framework, which accounts for exposure variability rather than relying on a single result.

Your report sets out the measured concentrations, the compliance position, the adequacy of existing controls such as local exhaust ventilation, and a recommended re-monitoring interval. It is written to be understood by managers and to satisfy HSE inspectors, auditors and insurers.

Our sulphur dioxide monitoring process

Our sulphur dioxide monitoring programmes follow a structured, four-stage workflow so the results stand up to scrutiny. Request monitoring or book a site assessment to begin.

1Scoping & site survey. We review your processes, COSHH assessments and previous sulphur dioxide monitoring data, then plan a representative sampling strategy using BS EN 689 similar exposure groups.
2On-site sampling. Qualified occupational hygienists carry out calibrated breathing-zone and static measurements across a representative shift, with full chain-of-custody documentation.
3Accredited analysis. Samples are analysed using the relevant MDHS / ISO laboratory method and the results are compared against the applicable workplace exposure limit.
4Reporting & recommendations. You receive a clear exposure report with compliance status, control recommendations and a re-monitoring interval — defensible evidence for HSE, insurers and auditors.

Frequently asked questions

What is the SO2 exposure limit?

Sulphur dioxide has a 15-minute short-term exposure limit of 0.1 ppm; its acute irritant effect makes short-term control important.

Where is SO2 monitoring needed?

Combustion and smelting operations, power generation, and food and beverage processes using sulphite preservatives.

Is SO2 harmful at low levels?

Yes — it is a potent respiratory irritant, particularly for people with asthma, so even short peaks must be controlled.