Phoenix Journal · LEV Testing
A local exhaust ventilation system that fails its test was almost always designed to fail, long before an examiner arrived. Get the hood, the ductwork and the test access right on the drawing board and the certificate looks after itself.
Designing for compliance
Most local exhaust ventilation systems that fail a thorough examination were never going to pass - the shortcomings were built in on the drawing board and only discovered years later when an examiner put a probe to the hood.
Under Regulation 9 of the Control of Substances Hazardous to Health Regulations 2002, engineering controls that protect people from hazardous substances must be thoroughly examined and tested by a competent person. For most systems that means at least every 14 months, and the guidance is clear that 14 months is a statutory ceiling rather than a target - Schedule 4 sets shorter minimums of six months or one month for higher-risk processes. The examiner works to the HSE's HSG258, ‘Controlling airborne contaminants at work’, and if the system cannot demonstrate that it controls the contaminant at source, it does not get a clean certificate.
The good news is that passing is not a dark art. An examiner is checking whether the system does what a competent designer said it would do, and whether you can prove it. Design with that examination in mind - the right velocities, honest test access and a commissioning benchmark to measure against - and the annual test becomes a formality rather than a gamble.
These are the choices that separate a system which sails through its examination from one that collects a red label. Work through them in order, because each one depends on the one before.
Engineers tend to think of a thorough examination as a physical inspection, and it is - but a large part of what the competent person signs off is whether the system matches its own documentation and controls to a defensible standard. HSG258 expects the examination to answer three questions: is the LEV in efficient working order, is it in good repair, and is it in a clean state. You can only answer the first if there is a design specification to compare against.
That is why the logbook matters as much as the metalwork. A well-designed system arrives with a commissioning report, a schematic showing the intended airflows at each hood, and a clear statement of the contaminant it was built to control. When the examiner can see that hood three was commissioned at a given velocity and reads close to it today, the visit is short and the certificate is straightforward. When there is no benchmark, the examiner has to fall back on published guidance and a good deal of professional judgement, and any doubt tends to land on the side of caution.
Competence sits on both sides of this. The person examining your system should hold a recognised qualification such as BOHS P601, and the person who designed it should be able to justify every velocity and duct size the same way. Combustion appliances add CO₂ and other products to the air a kitchen canopy has to move, wood machining throws dust with real momentum, and welding produces fume that carries known long-term health risks - each demands a different capture strategy, and none of them forgives a system sized by rule of thumb.
Finally, treat the design as a living thing rather than a one-off drawing. Records of examinations must be kept for at least five years, and every test, tweak and cleaning report becomes evidence of a system that is managed rather than merely installed. If the process changes - a new fryer, an extra machine, a busier shift pattern - the original design assumptions may no longer hold, and it is far cheaper to revisit them on paper than to discover the gap at the next examination.
A system built to control contaminant at source, sized to keep it moving, and fitted with honest test access is a system that passes its examination because it genuinely works - not because it scraped over a line. Everything the examiner measures, from capture velocity at the hood to static pressure across the fan, is something a good design fixes before the first shift ever runs. Get those decisions right and the annual certificate stops being a worry and starts being a receipt for work already done.
Questions
Under Regulation 9 of COSHH, LEV must be thoroughly examined and tested by a competent person at least every 14 months for most systems. That interval is a statutory maximum, not a default - Schedule 4 sets shorter minimums of six or one month for certain higher-risk processes, and your risk assessment may call for more frequent testing where wear would degrade performance sooner.
Capture velocity is the air speed the system generates at the point where the contaminant is released, drawing it into the hood against draughts and the process's own momentum. It is usually the first thing an examiner measures, because if the hood cannot capture the contaminant at source the rest of the system is irrelevant. Designing to a defensible capture velocity, and recording it at commissioning, is the single biggest factor in a clean result.
DW/172 is the recognised UK specification for commercial kitchen ventilation and following it gives you sound duct velocities, hood design and cleaning access, all of which help. However, DW/172 governs the ventilation design while the thorough examination is carried out under COSHH to HSG258, so you also need documented commissioning figures, accessible test positions and a maintained system to demonstrate control on the day.
Phoenix Duct Clean · by the numbers
Phoenix examines and tests local exhaust ventilation to HSG258 and COSHH - measured, reported and certificated, UK-wide.