Phoenix Journal · LEV Testing
A red mark on a thorough examination and test report is never really the beginning of the story. Here is how an LEV failure is built, stage by stage - and how to undo it.
LEV Testing
A red mark on a thorough examination and test report is rarely a surprise to the engineer who wrote it - and it should never be a surprise to you either.
When a local exhaust ventilation system fails its statutory check, the paperwork tends to land with a thud. A canopy that has run quietly over your line for years is suddenly labelled as not fit for purpose, and the report reads like a charge sheet. It is worth slowing down at that point, because a failed LEV test is not a single event. It is the visible end of a chain of small changes - a slackening belt, a loading filter, a damper nudged shut by a passing trolley - that quietly eroded control long before the engineer arrived with a meter.
Understanding how that failure is actually built, stage by stage, is the fastest route to fixing it properly rather than papering over it. Under COSHH Regulation 9, every LEV system must undergo a thorough examination and test - a TExT - at least once every fourteen months, and the report you receive follows a structure set out in the HSE guidance document HSG258, ‘Controlling airborne contaminants at work’. For commercial kitchen extraction specifically, the relevant sister guidance is SR17, ‘Controlling cooking fumes’. Once you know what each stage is checking, an anatomy emerges - and so does the cure.
A competent TExT is not a single measurement. HSG258 sets out three sequential stages, and a system can fail at any of them for entirely different reasons. Reading a report without knowing which stage triggered the failure is how good money gets spent on the wrong repair.
The first stage is a thorough visual and structural examination. Before any instrument comes out, the engineer confirms the system is complete, in good repair and in a clean condition - ducting intact, hoods undamaged, filters present and correctly specified, fan and motor sound, dampers set where they should be. A surprising share of failures never get past this stage. A collapsed flexible duct behind a fryer, a grease-clogged mesh baffle, or a filter simply missing from its housing will end the examination on visual grounds alone, because no measurement can rescue a system that is physically broken.
The second stage is technical performance measurement. Here the engineer takes readings - face velocity across the plane of a canopy or hood, capture velocity at the point where the contaminant is actually released, static pressure at test points along the ducting - and compares them against the system’s commissioning benchmark. This is the crux many operators miss. Face velocity is the speed of air entering the hood; capture velocity is the speed needed at the source to overcome the movement of the fume cloud and draw it in. A large canopy face is typically averaged across nine measured points, and if that average has drifted below the design figure, the system is no longer pulling contaminant where the cook is standing. Without a commissioning record to measure against, the engineer is left comparing your readings to generic benchmarks, which is a weaker footing and a common reason for a cautious or failed verdict.
The third stage is the assessment of control effectiveness, and it is the one most often underweighted. This is the qualitative confirmation that the system is genuinely controlling exposure at the worker’s breathing zone - smoke tests to visualise airflow, dust-lamp observation where relevant, and, for some processes, comparison of air monitoring against the applicable Workplace Exposure Limit. A system can pass on numbers and still fail here if the fume plainly rolls out past the canopy edge in use. Control, not airflow for its own sake, is the entire point.
The numbers behind the verdict
Most failures trace back to a handful of measurable thresholds and deadlines. These are the ones worth committing to memory before your next examination.
The fourteen-month figure carries a deliberate two-month margin over an annual cycle, so you can schedule sensibly without ever breaching the maximum - but it is a hard ceiling, and a lapse of even a day leaves the system uncertificated in the eyes of an inspector. The five-year retention rule means a failed report is not something to file and forget; it becomes part of the evidence trail that shows what you knew and when. And the multi-point face measurement matters because a single central reading can look healthy while the corners of a canopy leak - averaging across the face is what exposes an uneven, under-performing hood.
Once you strip the reports back, the same culprits recur across commercial kitchens and light industrial extraction alike. Very few are dramatic. Most are the slow accumulation of neglect meeting a measurement that finally names it.
The reason so many of these are avoidable is that a TExT is a snapshot, not a health regime. The regulation expects the system to be maintained between examinations, not resurrected the week before one. A thorough clean of the extraction and ductwork, a filter change and a belt check ahead of the visit will resolve the majority of the failures above before an engineer ever measures them. It also matters enormously who does the measuring - the person signing your report must be genuinely competent to interpret what the numbers mean, and the difference between a defensible verdict and a box-ticked one is real. If you are staring at a fresh red mark and want to understand the specific mechanism behind it, it is worth reading why your LEV failed its test this year, and if you are choosing who carries out the next examination, what makes someone competent to test your LEV is the question to settle first.
Questions
It means the system did not meet the required standard at one of the three HSG258 stages - visual examination, performance measurement, or control effectiveness. A failure does not automatically mean you must stop work, but it does flag that the system is not adequately controlling exposure and that remedial action is needed. The report will set out exactly which stage failed and what must be put right.
Under COSHH Regulation 9, a thorough examination and test must be carried out at least once every fourteen months. For commercial cooking fumes the relevant HSE guidance is SR17, which points back to the same statutory interval. The fourteen months is a maximum ceiling, so most operators schedule annually to leave a safe margin, and each report must be kept for five years.
Face velocity is the speed of air entering the hood or canopy, measured across its opening - often averaged over nine points on a large face. Capture velocity is the speed of air at the point where the contaminant is actually released, which must be high enough to draw the fume cloud into the hood. A system can show acceptable face velocity yet still fail if capture velocity at the source is too low to control the fume.
It depends on why it failed. Many kitchen extraction failures are caused by grease-loaded filters and dirty ductwork, which a thorough clean and filter change will resolve. Mechanical faults such as worn fan belts, damaged ducting or a system that was never properly commissioned need genuine repair or re-benchmarking. The most efficient approach is to clean, remedy any defects and then re-test in one coordinated visit.
Phoenix Duct Clean · by the numbers
Phoenix examines and tests local exhaust ventilation to HSG258 and COSHH - measured, reported and certificated, UK-wide.