How Are Fume Cupboards Tested? A Step-by-Step Guide
- Nexus Examination
- Jun 26
- 3 min read
A fume cupboard only does its job if it actually pulls hazardous fumes away from the person using it, and the only way to know it still does that is to test it. The trouble is that a cupboard can look perfectly fine while quietly underperforming. Here is how fume cupboards are tested, what gets measured, how often, and who is allowed to do it.
How Are Fume Cupboards Tested?
Fume cupboards are tested as part of a thorough examination and test, or TExT, carried out by a competent person at least every 14 months under COSHH. The test combines a visual inspection, measurement of face velocity and containment against the cupboard's design figures, and an assessment of whether it still controls exposure properly.
In other words, it is far more than a quick look. We carry out LEV examinations across Berkshire and the surrounding counties, and a fume cupboard is one of the most common types of local exhaust ventilation we test.
What the Regulations Require
Fume cupboards are a form of local exhaust ventilation (LEV), so they fall under Regulation 9 of COSHH. That requires a thorough examination and test at least every 14 months, carried out by a competent person, with records kept for at least 5 years.
The method follows the HSE's guidance, HSG258, and the fume cupboard standard BS EN 14175 for ducted units. You can read the HSE's guidance on LEV for the wider legal picture.
The Three Stages of a Fume Cupboard Test
A proper test follows the three stages set out in HSG258. Each one builds on the last.
Stage 1: Visual and Structural Inspection
The examiner checks the physical condition of the cupboard and the system behind it: the sash and glass, the seals, the ductwork, the fan, and any alarms or signage. Damage, wear or a staining around joints can all point to a problem before any measurements are taken.
Stage 2: Measuring Performance
This is the technical heart of the test, comparing the cupboard's current performance against its original commissioning figures. Typically this involves measuring:
Face velocity across the sash opening, taken at a grid of points and usually in the region of 0.3 to 0.5 m/s
Containment, often using a tracer gas such as sulphur hexafluoride, in line with BS EN 14175
Airflow direction, shown with a smoke or visualisation test to prove air moves into the cupboard
The condition and function of any low-airflow and sash alarms
The results measured against the cupboard's design and commissioning values
A fume cupboard testing visit covers all of this, because face velocity alone does not prove the cupboard is safely containing fumes.
Stage 3: Assessing Control of Exposure
The final stage steps back and asks the real question: does the cupboard actually control exposure for the work being done in it? A cupboard can pass its velocity readings and still be unsuitable for a particular process, so this judgement is what ties the test back to protecting the user.
How Often Should a Fume Cupboard Be Tested?
The legal minimum under COSHH is at least every 14 months. In practice, many organisations test annually to keep it simple, and schools follow CLEAPSS G9 guidance on a yearly basis. Some higher-risk processes need testing far more often, as set out in HSG258.
If a fume cupboard fails, it should be taken out of use, repaired and re-tested before anyone relies on it again.
Who Can Test a Fume Cupboard?
Testing must be done by a competent person with the right training, knowledge and equipment, and the examiner should be impartial. Someone with a stake in the outcome is less likely to fail a borderline cupboard, which is exactly why independence matters. Our thorough examination services are kept separate from installation and repair for that reason.
Why It Matters
The substances a fume cupboard handles can cause serious, often irreversible respiratory harm, and the damage tends to show up years later. By then it is too late to do anything about it.
Testing is what turns a fume cupboard from a box you hope is working into one you know is working. A cupboard that looks fine can be failing to contain fumes, and the only way to tell the difference is to measure it properly, on schedule, by someone who knows what good looks like.
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