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Case study · Food manufacturing · Process extraction
A dairy processing yoghurt ran extraction over its pasteurising and filling lines - partly for the steam, but mainly for the cleaning chemicals used to keep the plant hygienic. The control was effective. The interesting finding was not a fail, but condensation gathering where it should not. Here is what food-process LEV has to deal with.
The site
The plant processes and fills yoghurt - a business of hot pasteurising, culturing and filling, followed by rigorous cleaning to keep everything hygienic. Extraction runs over the processing and filling machinery, in hygienic stainless ductwork built to survive constant wash-down.
From the outside, you might assume the extraction is there for the steam. It is partly - hot process and filling throw off steam and fine aerosol. But the harder-working half of the job is the cleaning. Dairies run clean-in-place (CIP) cycles that pump caustic detergents, acid descalers and sanitisers through the plant, and those chemicals give off vapours and mists that are genuinely hazardous to breathe. The LEV has to handle both worlds: the warm, wet aerosol of production and the chemical vapour of the cleaning cycle.
That dual duty, and the wash-down environment, make food-process extraction its own discipline. The examination had to judge not only whether the system captured what it should, but whether it coped with being warm, wet and chemically loaded day in, day out.
The hazard and the law
It is easy to focus on the steam and overlook the chemistry. The substances that actually trigger the COSHH duty here are the cleaning agents: strong alkaline (caustic) detergents, acid descalers such as nitric or phosphoric acid, and sanitisers such as peracetic acid. These irritate the eyes, skin and airways, and their vapours need controlling at source during every cleaning cycle. The process steam and aerosol add heat, moisture and a microbial dimension on top.
Where extraction is provided to control exposure to those substances, it is local exhaust ventilation and falls under Regulation 9 of COSHH - a thorough examination and test at least every 14 months, with the record kept. The distinctive challenge in a dairy is that the system is judged not just on capture but on whether it can go on capturing in a warm, wet, wash-down environment without becoming a hygiene problem of its own.
What we tested
We measured the capture and extract airflow at the processing and filling points, inspected the stainless ductwork, fan and filtration, and ran a qualitative check that steam, aerosol and cleaning-chemical vapour were drawn away cleanly rather than drifting across the production floor. During a cleaning cycle, the question is whether the vapour coming off the CIP is captured at source before anyone breathes it.
Because this is food, we went further than a dry-process examination would. We looked specifically at how the ductwork handled the warm, wet air it carries - where condensate forms, whether the runs drain, and whether any pooling had developed in low points. In a food plant that is not a side issue; it is where a compliant system can quietly turn into a hygiene risk.
What we found
| Check | Finding | Result |
|---|---|---|
| Capture at process / filling | Steam and aerosol drawn away cleanly | Pass |
| CIP vapour capture | Cleaning-chemical vapour controlled at source | Pass |
| Extract airflow / fan | Within benchmark; fan running true | Pass |
| Condensation / drainage | Condensate pooling in a duct low point - no drain | Advisory |
The control was effective: the system captured the process steam and aerosol and, importantly, the cleaning-chemical vapour during CIP, and the extract airflow met benchmark with the fan running true. The system was doing its job. The one thing worth fixing was not a control failure but a consequence of handling wet air - condensate had gathered in a low point of the ductwork with nowhere to drain, where over time it becomes a hygiene and corrosion issue. A pass on exposure control, with a condensation advisory to close out.
The advisory
The outcome
The dairy left with a dated record showing effective control of both process aerosol and cleaning-chemical vapour, plus a simple drainage fix to stop the condensation becoming a problem. The examination did what a good one should in a food plant - confirmed the exposure control and caught the hygiene issue before it developed.
The takeaway is that process extraction in a food environment is doing two jobs at once - controlling exposure and staying hygienic - and the second is where it tends to drift. The chemicals of the cleaning cycle are the real COSHH hazard, often overlooked behind the obvious steam, and the warm wet air those systems carry will find any low point in the ductwork and sit there. Testing on the 14-month cycle, with an eye on drainage and condensation as well as airflow, keeps a food-side system both compliant and clean.
Sources and further reading
The duties, exposure limits and control standards described here come from the Health and Safety Executive. For your own process, always work from the current HSE guidance:
Questions
Partly for the steam and aerosol that come off hot processing and filling, but mainly for the chemicals used to keep the plant clean. Dairies run clean-in-place (CIP) cycles using caustic, acid and sanitiser solutions, and the vapours and mists from those are hazardous to health. Extraction over the lines keeps steam, process aerosol and cleaning-chemical vapour out of the operators' breathing zone.
Clean-in-place systems typically use strong alkaline (caustic) detergents, acid descalers such as nitric or phosphoric acid, and sanitisers such as peracetic acid. All can irritate the eyes, skin and airways, and some give off vapour that needs controlling at source. The LEV is what captures that vapour during cleaning cycles as well as handling the process steam during production.
We measure the capture and extract airflow at the process and filling points, inspect the ductwork, fan and any filtration, and run a qualitative check that steam, aerosol and vapour are being drawn away rather than drifting across the room. Because this is a food environment, we also look at hygiene-specific issues such as condensation and wash-down resistance that a dry-process system would not have.
Food-process extraction handles warm, wet air, which condenses on cooler duct surfaces. If the ductwork does not drain, that condensate pools in low points, where it can harbour microbial growth, drip back toward the process, and in time corrode or add weight to the duct. On the food side, a duct that cannot drain is both a hygiene risk and a maintenance problem - which is why we flag it even when the airflow itself passes.
Because a pass on control does not mean the system is perfect. Here the capture was effective, but condensation was gathering in a duct low point with no drainage. Left alone it becomes a hygiene and corrosion issue, so we recorded it as an advisory with a clear fix. Acting on advisories keeps a compliant system from developing a real problem before the next test.
At least every 14 months under COSHH, like any other LEV, and sooner if the process or the cleaning regime changes. In a food plant it is also worth aligning the examination with a planned maintenance or deep-clean window, when lines are down and the ductwork can be inspected and drained properly.
Tell us your capture points and the process they control, and we will quote the thorough examination and test to COSHH and HSG258.
