Phoenix Journal · LEV Testing
In a distillery or brewery the air itself carries process risk - ethanol vapour off the stills and carbon dioxide off fermentation both need moving before they reach people or an ignition source. Here is how the two ways of controlling that fume compare.
Ventilation & fume control
In a distillery or brewery the air itself is part of the process risk - ethanol vapour rolling off the wash and the stills, and carbon dioxide pouring off fermentation, both have to be moved before they reach a person or an ignition source.
These are two very different hazards that happen to share the same room. Carbon dioxide is the quiet one. Fermentation throws off huge volumes of it, it is colourless and odourless, and because it is heavier than air it pools at low level - in fermentation cellars, tank pits, floor channels and confined vessels. The workplace exposure limits under HSE guidance note EH40 are 5,000 ppm over an eight-hour day and 15,000 ppm over any fifteen-minute period. Well before those figures a worker feels headache, breathlessness and a racing pulse; well above them, in a poorly ventilated pit, the risk is loss of consciousness and asphyxiation.
Ethanol vapour is the loud one. Every open vessel, spirit safe, cask-filling point and warm still surface gives off a flammable vapour whose lower explosive limit sits at roughly 3.3% by volume in air. Once vapour builds towards that band, any spark, hot surface or static discharge can ignite it. That is why stillhouses and spirit stores are assessed under DSEAR, classified into hazardous zones, and fitted with ATEX-rated fans, motors and electrics wherever vapour can reach explosive concentrations.
Controlling both comes down to one choice, made hotspot by hotspot: do you dilute the whole space so nothing ever reaches a dangerous concentration, or do you capture the fume at the point it is released? Most sites end up doing both, but the two approaches behave very differently, so it is worth weighing them side by side.
Dilution, or general, ventilation floods the space with fresh air and sweeps the contaminated air out, keeping the average concentration across the room comfortably below the exposure and explosive limits. It is the traditional answer in tall, open stillhouses and fermentation halls where the release is spread out and hard to hood.
Local exhaust ventilation - LEV - puts a hood, slot or canopy right where the vapour or gas is given off and draws it away before it can reach the breathing zone. Instead of treating the whole room, it targets the worst points: the spirit safe, cask-filling stations, sample and racking points, the charging of a mash tun.
In practice the two are partners, not rivals. Dilution ventilation manages the diffuse background - the CO₂ across the room and the general vapour load - while LEV takes the concentrated hotspots off at source. A DSEAR risk assessment and a COSHH assessment together decide where each belongs, and low-level CO₂ extract or fixed gas detection is usually added on top for the pits and cellars where gas collects.
Whichever route you take, the law expects evidence, not good intentions. Under the Control of Substances Hazardous to Health Regulations you have to keep exposure to ethanol vapour and carbon dioxide below their limits and prove the controls stay effective. For LEV that means a Thorough Examination and Test - carried out to HSE guidance HSG258 by a competent person, typically someone holding the BOHS P601 qualification - covering airflow readings, capture velocity, duct velocity, filter and fan condition and a full review of how well the system actually contains the fume. Records must be kept for at least five years, and the DSEAR zoning and gas detection sit alongside as their own duty. Get the design, the balance and the testing right and both hazards stay where they belong - in the plant, not in your people.
Questions
Any local exhaust ventilation used to control ethanol vapour or other hazardous substances must have a Thorough Examination and Test at least every fourteen months under COSHH Regulation 9. The work should follow HSE guidance HSG258 and be done by a competent person, usually one holding the BOHS P601 qualification. You must keep the test records for at least five years. Some higher-risk processes need testing more often, so your COSHH assessment sets the exact interval.
Often not. Dilution ventilation handles diffuse, low-level fume well, but it does nothing at the point of release and struggles with carbon dioxide, which is heavier than air and pools in pits, cellars and floor channels. Most sites combine dilution for the general background with local exhaust ventilation at hotspots such as the spirit safe and cask-filling points, plus dedicated low-level CO2 extract or fixed gas detection. A DSEAR and COSHH assessment decides the right mix for your building.
Two very different ones share the same space. Carbon dioxide from fermentation is an asphyxiation risk - its workplace exposure limits are 5,000 ppm over eight hours and 15,000 ppm over fifteen minutes, and it collects at low level. Ethanol vapour from the wash and stills is flammable, with a lower explosive limit around 3.3% by volume, which is why stillhouses are assessed under DSEAR, zoned, and fitted with ATEX-rated equipment.
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