SiteIt's Wednesday afternoon. The weld bay's running flat out on a rush order. Above booth 3 the extraction is humming, so everyone assumes it's working.
The hood's airflow indicator has been in the red since Monday. The fan belt is slipping. The filter hasn't been changed since spring. The test label on the hood says the next exam was due in March.
Extraction fails quietly. Nothing stops, nobody gets a fault on the HMI, and the fume just stays where people breathe.
Most sites book the test. What catches them is the 14 months in between, when nobody owns the system.
What the 14 months means
COSHH says local exhaust ventilation must have a thorough examination and test "at least once every 14 months"* (regulation 9). HSE's leaflet puts it simply. Most systems are tested once a year, and legally "you are allowed no more than 14 months"* between tests (INDG408).
Some processes need it far more often. Schedule 4 sets the shorter gaps (Schedule 4):
- blast cleaning of metal castings: every month*
- dry grinding, abrading or polishing of metal with power tools, in any room for more than 12 hours a week*: every 6 months*
- dust or fume from making non-ferrous castings: every 6 months*
That second one catches maintenance workshops and fabrication shops. If your fitters run bench grinders and flap discs for more than 12 hours a week* in the same room, the extraction is on 6 months*, not 14.
The same regulation asks you to keep the extraction "in an efficient state, in efficient working order, in good repair and in a clean condition". You must keep a record of each test, and of repairs that came from it, for at least 5 years*.
What the examiner actually does
The test checks the system against what it was designed to do. HSE says it "tests the LEV against the performance recorded in the commissioning report". That means airflow and pressure readings, checks on how well it controls exposure, and sometimes air sampling (INDG408).
So the examiner needs the design figures. HSE asks you to hand over the commissioning report, the user manual and the logbook. Without the commissioning data, "you will not know whether your system is working correctly". You may need the system commissioned first. The same goes if you've changed the process or layout since it was last commissioned.
That last point bites after a rebuild. New machine, hood moved a metre to fit, a branch added to the duct. Nobody tells the extraction. HSE's advice is blunt: "Don't assume it will cope. Get the LEV system recommissioned" (INDG408).
Red label means stop
A hood that's clearly failed gets a red fail label, and HSE says urgent action is needed. If the test shows the extraction isn't controlling exposure, HSE says to "stop the work and repair the LEV". If work has to carry on meanwhile, people need extra protection such as RPE (INDG408).
Read the action plan the day it arrives. HSE treats a long list of repairs as a sign "that your checking and maintenance is not good enough". We'd go further. If the examiner keeps finding the same faults, your checks between tests have stopped happening.
Between tests is your job
The test is once a year at most. The extraction runs every shift. HSE splits the checks into four kinds of part (INDG408):
- moving parts that wear, like fan bearings and filter shakers
- hoods, ductwork and seals
- parts that wear out with use, like filters and flexible duct
- jobs that need doing regularly, like filter changes
You can't judge hood airflow by holding your hand up. HSE says so (HSE, LEV FAQs). Airflow indicators aren't a legal must, but HSE's guidance recommends them, and they're the only check that shows the operator a problem at once. Strips of paper hung in the hood don't count.
Put the daily check with the operator and the weekly one with the shift fitter, and log both. HSE's leaflet has the works engineer down to repair faults, carry out maintenance and arrange the test. Most sites have someone doing that. Fewer have it written down.
When the extraction breaks down
It's 4pm on a Friday and the extraction fan on the grinding bay trips. Production wants to keep going. "It's only an hour."
This is a breakdown like any other, and it needs the same urgency as a stopped line. Running the process with the extraction off means people breathing what it was put in to remove. If you can't fix it, stop that work or protect the people doing it.
Many LEV faults are ordinary maintenance faults. A motor tripping on overload, which our guide to motor overload trips walks through. A fan out of balance from built-up dust, covered in our post on fans and blowers. A blinded filter. A split flexible duct. Your shift fitter can fix most of them, as long as someone has spares and knows the system.
Two cautions. Inside the duct and the filter housing is where the contaminant collects. HSE says that where the system can be contaminated with toxic substances, you may need permits to work and formal method statements (INDG408). See method statements for breakdown work. And dust that builds up in ducts and filters can burn, so think about fire risk from dust and hot work before anyone grinds or welds near it.
Who can test it
The examiner must be competent, and HSE says a training course alone doesn't make them so. Competence is knowledge, skills and experience together (HSE, LEV FAQs). Ask what systems like yours they've tested, and ask for a report that sets readings against design figures.
Hired on-tool extraction units need testing too. The hire firm owns the unit and the duty to test it. But HSE says you're responsible for not using it once the test has expired while it's on hire to you.
For the wider picture, see our post on COSHH in the maintenance workshop.
What to do on Monday
- List every extraction system on site with its last test date. Book any that are near 14 months*.
- Check whether any grinding or polishing area runs more than 12 hours a week*. If so, move it to 6 months*.
- Find the commissioning report for each system. If you can't, ask your examiner what they need.
- Add a daily airflow check for operators and a weekly one for fitters, and keep a spare belt and filter set for each fan.
* The 14-month test interval, the Schedule 4 intervals and the 12-hour threshold, and the 5-year record period correct as of 4 October 2026. Check COSHH regulation 9 on legislation.gov.uk and HSE's LEV pages for the latest.