Workplace Airflow Testing
Airflow & IAQ · Airflow & IAQ overview
Workplace airflow testing is the structured measurement of how air moves into, through and out of a workplace, and how that movement controls — or fails to control — airborne contaminants. It is the technical foundation under LEV testing, ventilation performance assessment, indoor air quality investigations and odour complaints.
What workplace airflow testing is
Airflow testing uses calibrated instruments to quantify air velocity, volume flow, pressure and direction at defined points across a workplace. Measurements are recorded at supply diffusers, extract grilles, LEV hood faces, duct traverses, doorways and transfer openings, and compared against design intent, HSE guidance such as HSG258, and the contaminant control objective for each area.
Unlike a quick spot reading, a proper airflow test is structured: locations are chosen to represent how air actually moves through the space, the system is tested under normal operating conditions, and results are recorded in a form that can be repeated at the next test interval.
Why airflow testing matters
Airflow is the mechanism by which ventilation controls exposure. If the air is not moving in the right volume, at the right velocity, in the right direction, then no amount of installed plant will deliver the protection the COSHH risk assessment assumes. Many exposure problems and IAQ complaints in UK workplaces trace back to airflow shortfalls that were never measured.
Testing also gives organisations a defensible record. When an HSE inspector, insurer or client asks how the workplace knows its ventilation is working, calibrated airflow data tied to design benchmarks is a substantially stronger answer than visual inspection alone.
What can be measured or observed
A full airflow test combines instrument measurement with qualitative observation. The aim is to describe what the air is doing, not just to record a number.
- Capture and face velocity at LEV hoods and booths.
- Duct transport velocity and total extracted volume from pitot or vane traverses.
- Supply and extract volumes at diffusers and grilles, and the resulting supply/extract balance.
- Room pressure differentials between contaminated and clean zones.
- Direction of airflow across doorways, transfer grilles and process boundaries using smoke or tracer methods.
- Visible behaviour of contaminant clouds under dust lamps or smoke generators near sources.
How airflow testing supports other investigations
Airflow data is rarely an end in itself. It feeds the broader investigations that organisations actually need to make decisions. LEV testing under COSHH Regulation 9 depends on capture and duct velocities. Ventilation performance assessment combines airflow with system condition and user-practice observations. Indoor air quality and odour investigations rely on direction-of-flow and pressure data to explain where contaminants and smells are coming from.
Because airflow testing underpins all of these, a single competent airflow survey often answers questions that previously required separate visits from multiple disciplines.
Common airflow problems
Airflow problems are often invisible. They show up as exposure complaints, intermittent odour incidents, comfort issues or unexpectedly poor LEV test results.
- Extract volumes well below design, usually from loaded filters, fan wear or duct restriction.
- Supply and extract out of balance, leaving rooms over- or under-pressurised relative to neighbouring areas.
- Reverse flow across doorways, drawing contaminants from production areas into offices, canteens or stores.
- Short-circuiting between supply diffusers and adjacent extract grilles, so fresh air leaves before it reaches the breathing zone.
- Dead zones with no measurable air movement, allowing contaminants and odours to accumulate.
- Draughts from doors, roller shutters or cooling fans that overwhelm capture at LEV hoods.
When airflow testing should be requested
Airflow testing is appropriate before a statutory LEV test where the system has been altered, after building works or changes to layout, when a new process is introduced, in response to exposure complaints, where IAQ or odour issues are reported, and as part of a structured ventilation review every one to two years for higher-risk operations.
It is also a useful first step before committing to capital expenditure on new ventilation. Measuring what the existing system actually delivers usually reveals lower-cost improvements before any equipment is replaced.
Frequently asked questions
Is airflow testing the same as LEV testing?
No. Airflow testing measures air movement; LEV testing under COSHH Regulation 9 is a formal thorough examination and test of an extraction system against its design intent and HSE HSG258 benchmarks. LEV testing relies on airflow measurements, but also covers system condition, capture observation and user practice.
How often should workplace airflow be tested?
Statutory LEV systems are tested at least every 14 months. General workplace airflow, supply/extract balance and pressure relationships should be reviewed whenever processes, layout or building services change, and periodically as part of a planned ventilation programme — typically annually for higher-risk environments.
What instruments are used?
Calibrated vane anemometers, hot-wire anemometers, pitot-static tubes with micromanometers, capture-hood balometers, and smoke or tracer methods for direction-of-flow observation. Instrument calibration certificates are part of the audit trail.
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