Designing and managing local exhaust ventilation


Local exhaust ventilation (LEV) is one of the main measures used to control worker exposure to hazardous substances. It’s difficult to work out exactly how many systems there are in Britain, but the Health and Safety Executive carried out some research in 2006 and estimated that there were between 260,000 and 330,000 businesses that have LEV. Now some of these will be small organisations who will only have installed one system but many others will have several systems in place. So, if the HSE’s estimates are still valid, the total number of systems could be approaching half a million.

As with any engineering control (or other plant and equipment for that matter), if LEV is to work effectively it must be well designed and than managed properly.

Sadly, experience suggests that this is rarely the case. In practice

  • Many suppliers fail to consider the nature of the process and the behaviour of the contaminants when designing extraction hoods.
  • Inappropriate, “off the shelf” systems are installed
  • Proper commissioning is rarely undertaken.
  • Most suppliers don’t provide detailed instructions and other information needed by the client on use, maintenance and testing.
  • Once systems are installed many companies don’t carry out planned routine maintenance and testing.
  • Where testing is carried out it normally only comprises an annual “thorough examination and test” with no interim checks on condition or performance.
  • The standard of the “thorough examination and test” is often poor. Many testing companies only carry out flow and pressure measurements and do not evaluate the effectiveness of the system at controlling the contaminants.

The HSE recognised these problems and, following extensive stakeholder consultation, published updated guidance in HSG258 Controlling airborne contaminants at work: A guide to local exhaust ventilation.

I’ve uploaded a presentation to Slideshare about “Effective design and management of LEV” which summarises many of the key points from HSG258.

To attempt to improve awareness of good practice amongst managers a new one day BOHS Approved course – Practical Management of LEV Controls has been developed in conjunction with HSE. We’re going to be running it on 15th September 2011 in Chester. Cost £195.00 plus VAT per delegate (includes course documents, lecture fees and lunch). The above presentation gives a flavour of the course content.


Published by ms6282

I'm a consultant and trainer specialising in the recognition, evaluation and control of health hazards in the workplace. I'm based in the North West of England, but am willing to travel (almost) anywhere

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