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LEV testing - spray booths
A spray booth is one of the few places where the extraction that protects lungs is also the extraction that keeps a flammable atmosphere below the point it could ignite. That double duty is why booth testing is its own discipline.
The short answer
A spray booth is an LEV control that has to satisfy two regimes at once. Under COSHH it must capture paint mist and solvent vapour to protect health - and paints containing isocyanates are the single biggest cause of occupational asthma in Britain. Under DSEAR it must keep the flammable atmosphere below the level at which it could ignite. Testing a booth means checking it does both jobs, not just one.
The health duty
The first job of a spray booth is health protection. Spraying releases a fine mist of paint and a cloud of solvent vapour, and the booth's airflow has to capture and carry that away from the sprayer's breathing zone. Where the paint contains isocyanates - common in two-pack automotive and industrial finishes - the stakes are high: isocyanates are the leading cause of occupational asthma in Great Britain, and exposure has to be controlled tightly.
That is why booths fall squarely under COSHH and its Regulation 9 duty to examine and test the LEV at least every 14 months. It is also why health surveillance is mandatory for workers exposed to isocyanates - the control and the monitoring go together, because the harm is serious and can develop with little warning.
The fire duty
The same airflow that protects the sprayer also controls a fire and explosion risk. Solvent vapour and fine paint mist are flammable, and in a poorly ventilated booth they can build to a concentration that will ignite. The recognised booth standard sets the minimum airflow needed to keep the flammable material below its lower explosive limit everywhere except right at the spray gun - so the ventilation is a fire-safety control as much as a health one.
Because of that, spray booths also engage DSEAR, the regulations covering dangerous and explosive substances. DSEAR requires the flammable risk to be assessed, zones where an explosive atmosphere may occur to be classified, and equipment in those zones to be suitably rated - so that nothing inside the booth can become the ignition source the ventilation is working to avoid.
Where they meet
The overlap is what makes booth testing distinctive: a single airflow has to be adequate for two different purposes at once. Enough to capture the mist and vapour for health, and enough to keep the atmosphere below the explosive limit for fire. A booth that is marginal can fail one duty while appearing to meet the other, which is why the testing has to hold the airflow against both standards, not just the health one.
Clearance is part of that picture. A smoke clearance test measures how long the booth takes to clear after spraying - relevant both to when it is safe to enter and to how long a flammable atmosphere lingers. Booth testing therefore looks at capture, at airflow against the explosive limit, and at clearance time together.
What proper testing covers
A competent spray booth examination goes well beyond a single reading. It checks the airflow through the booth against the design and the standard, examines the filters and the fan, looks at the condition of the enclosure and the extraction, and considers the DSEAR picture - whether zoning and equipment ratings are being maintained. Smoke visualisation is often used to see capture and clearance directly.
The output is a thorough examination and test report that says whether the booth is controlling exposure and keeping the atmosphere safe, with any remedial actions. Because two duties ride on the same equipment, cutting corners on booth testing is a poor bet - a booth that quietly under-performs is failing on health and fire at the same time.
Keeping it right
Booths degrade in ways that hit both duties. Loaded filters and a tiring fan reduce airflow, which simultaneously worsens capture and lets the flammable atmosphere build - so filter changes and maintenance between tests are not housekeeping but a genuine control measure. A booth run on tired filters is quietly eroding its protection on both fronts.
That makes the maintenance regime between the statutory tests as important as the tests themselves. Keeping the filters, the airflow and the enclosure in good order is what holds a booth at the performance its examination confirmed - protecting the sprayer's lungs and keeping the fire risk in check at once.
Questions
Because the same airflow does two jobs: capturing paint mist and solvent vapour to protect health under COSHH, and keeping the flammable atmosphere below the level it could ignite under DSEAR. Testing has to check both.
Isocyanates are the single biggest cause of occupational asthma in Great Britain. Exposure must be controlled tightly, and health surveillance is mandatory for workers exposed to them.
Assessing the flammable risk, classifying zones where an explosive atmosphere may occur, and ensuring equipment in those zones is suitably rated - so nothing in the booth becomes an ignition source.
At least every 14 months under COSHH Regulation 9, like other LEV - and testing should check airflow against both the health capture duty and the explosive-limit fire duty.
A test that measures how long a booth takes to clear after spraying - relevant both to when it is safe to enter and to how long a flammable atmosphere lingers.
Because loaded filters and a tiring fan reduce airflow, which worsens capture and lets the flammable atmosphere build at the same time - eroding both the health and the fire protection.
We examine spray booths for capture and for airflow against the explosive limit, so one report covers health and fire.
