Diagnostics & problems
Local exhaust ventilation fails quietly. Long before a thorough examination fails it, the system leaks warning signs onto the shop floor: dust where there should be none, a smell that should have been drawn away, people feeling unwell. Learn to read them.
The short answer
A working fan is not proof of a working system. The signs that extraction has stopped protecting people show up on the floor first: settled dust, lingering smells, symptoms in staff, a change in the sound of the plant, and a system that only just scraped through its last test. Any one of them is a reason to have the system examined.
The detail
The first sign is dust you can see settling on surfaces, ledges and window sills. If the coarse fraction is landing where you can see it, the fine respirable fraction that you cannot see has already travelled through the breathing zone. The second is smell: if a solvent or process odour lingers while extraction runs, vapour is reaching noses instead of the hood. The third is people, not plant. Headaches, throat and eye irritation, tightness of chest or a cough that eases on days off all point to something airborne that the system should be removing.
The fourth sign is a change in how the plant sounds: a system that has grown noticeably louder while pulling less, or a new whine, rattle or roar, is often a blocked filter, a worn fan or a leaking duct. The fifth is a paper trail one: a system that only just passed last time, carried an amber note, or is overdue its examination has little headroom left. Under COSHH Regulation 9 the duty is to keep the control in efficient working order and to examine it at least every fourteen months, and that fourteen months is a legal ceiling, not a maintenance plan.
What it means for you
Every one of these signs is a lagging indicator. By the time dust is visible, a smell lingers or a worker feels unwell, exposure has already been happening, often for a while. That is the trap with airborne hazards: the harm is cumulative and largely invisible until it is done. The Health and Safety Executive estimates around 22,000 new cases of breathing and lung problems caused or made worse by work each year, and around 12,000 deaths a year from occupational lung disease, most of it from exposures years or decades earlier.
The right response to any of these signs is not to turn the fan up or open a window, but to have the system examined against how it was designed to perform. A thorough examination and test measures capture at source, airflow and pressures, and compares them to the commissioning benchmark, so it catches the fault behind the symptom before the symptom becomes a claim. The signs tell you something is wrong; the test tells you what, and by how much.
The service behind the guide
When the floor is giving off warning signs, guessing is expensive. We examine the system against its design, measure what each hood is actually capturing, and hand you a report that says plainly which controls are working and which are not.
Questions
Visible settled dust, a lingering process or solvent smell while extraction runs, staff reporting headaches or irritation, a change in the sound of the plant such as a new whine or a louder but weaker draught, and a system that only just passed its last test or is overdue one.
No. A running fan only proves a motor is turning. Capture happens at the source, and every link between the source and the fan can fail while the fan still runs. The only way to know is to measure capture and airflow against the design.
At least every fourteen months under COSHH Regulation 9, and more often for arduous duties. That interval is a legal maximum, not a target: a system can drift out of control well within it.
They are strong reasons to act, not a measurement. Because airborne exposure is largely invisible and its harm is cumulative, the signs tend to appear after exposure has been happening. A thorough examination, and where needed air sampling, turns suspicion into evidence.
Have the system examined against its design rather than simply turning the fan up or opening a door. A thorough examination and test identifies the fault behind the sign and sets out the remedial actions needed.
Phoenix Duct Clean · by the numbers
If any of these signs sound familiar, a thorough examination and test will tell you which hoods are still controlling exposure and which are not. Call for a straight answer and a dated report.