COSHH / LEV Testing

LEV Testing    


Are your LEV systems up to the job of protecting users adequately?

The COSHH Regulations1 require employers to prevent or control exposure to hazardous substances by their employees and people affected by their activities.  Since inhalation is the most significant route of exposure to hazardous substances, it follows that Local Exhaust Ventilation (LEV) becomes a useful measure to control and capture these substances as they are released into the atmosphere within the workplace.

Main LEV Components

LEV is a ventilation system that takes dusts, mists, gases, vapour or fumes out of the air so that the workers or anyone in the workplace cannot breathe them in.  An LEV system typically consists of the following components (see figure 1):


Hood(s) to collect airborne contaminants at, or near, where they are created.
Ducts  to carry airborne contaminants away from the process.
Air Cleaner  to filter and clean the extracted air
Fan which is of the correct size and type to provide sufficient extraction.
Discharge  the safe release of cleaned and extracted air into the atmosphere.

For an LEV system to work effectively, each of these components has to be selected and designed carefully, taking into consideration the work process it is intended to control.

What is the Problem?

LEV systems have been used in industry for a number of years and they come in various shapes and sizes.  So what is the problem?

LEV can be a very effective way of controlling exposure by removing contaminants from the workplace air, but the HSE says that much of the equipment in use doesn’t work.  The main problems are:

1. Employers often don’t appreciate the extent of exposure risk from their process.
2. Employers and employees are often over-optimistic about LEV capabilities and performance.
3. There has been no guidance on LEV buying and employers are often mislead and mis-sold.
4. As regards the LEV design, often the LEV hood is not matched to the process and sources causing exposure.
5. The LEV system is neither installed nor commissioned thoroughly.
6. The regular checking and maintenance of the LEV systems is often neglected.
7. The thorough examination and test as required under COSHH regulations is often not done or incomplete (it is not “thorough”).

Recent statistics from the HSE2 show that occupational disease and exposure affect many workers.  Thousands of people in the UK die of lung disease or get asthma because of airborne contaminants they have breathed in at work.  The cost to industry for occupational asthma is £96-135 million and it is on the increase each year.  Health risks need to be better controlled and a disease reduction programme is being promoted by the HSE.

What is the Solution?

The HSE has recently published revised guidance on LEV, including booklets for employers, designers, installers and examiners and pocket cards for workers.  Following a major re-write, new and improved LEV guidance is now available (see  The changes are so significant that the HSE felt the need to provide additional training for their Inspectors and over 400 have been trained and issued with simple test equipment. 

As part of a campaign to raise standards, the HSE launched Trainer, Advisor Briefing Days last year.  ESL consultants were invited to the first briefing day on 24th October 2008 at the Health & Safety Laboratory in Buxton.  The new LEV course training material (presentations, video clips, etc) was given to those attending the briefing, free of charge, subject to terms and conditions.  The HSE is doing this because they are looking for a step change in the understanding and application of LEV systems.

In addition to the above, the HSE has published documents3,4 which should provide employers, managers and health and safety officers with assistance in meeting their legal duties under the Management of Health & Safety at Work and COSHH Regulations5.

Specialist Help

Unless you have a fairly simple process to control, you probably need to get specialist help when it comes to purchasing a new LEV system.  There are some third party consultants who will act as advisers but most people will be dealing directly with an LEV supplier.  It is therefore important you select and vet any potential suppliers carefully.  The following questions might prove useful:

1.  What experience do they have in designing and providing LEV?
2.  What are their professional qualifications, experience and affiliations?
3. Have they successfully applied LEV to similar processes or activities in your industry?
4. Can they provide references or examples showing successful installation of LEV systems?
5.  Are they tied to a particular range of LEV products?
6.  How will they show that the LEV provides adequate control?

It is important that you give the supplier a specification of the work that you want to have done and what the proposed system should achieve.  One of the areas where specialist help might be needed is the annual examination and test of the LEV systems.  What are the requirements of the HSE’s revised guidance?

LEV Thorough Examination and Test (HSG 258)

Most LEV systems need a thorough examination and test once each year although COSHH specifies that you are allowed 14 months between tests.  This is a legal requirement to ensure that the LEV works well and continues to protect users.  Some LEV systems need more frequent thorough examination and testing, e.g. systems that are used to control critical or high hazard processes. 

Someone who is “independent” of the maintenance of the system should undertake the thorough examination and test.  In practice, this normally means hiring in an outside contractor.  Whatever the case, the following summarises what is required in order to carry out thorough examination and test under the new HSG 258:

LEV Examiner

1.   The examiner must be competent
2.   The examiner must be provided with:
· Commissioning report
· User Manual which should cover details of any thorough examination and testing work
· Log Book recording checks and maintenance activities
·  Full access to the systems and the co-operation of relevant staff
3. If no commissioning report or manual is available, the system  will need to be retrospectively commissioned.

Thorough examination and testing of LEV system involves three stages:

Step 1: A thorough visual examination to verify “….in efficient working order, in good repair and in a clean condition” – COSHH Regulation 9(1).
Step 2:  Measuring and examining the technical performance to check conformity with commissioning data
Step 3:  Assessment to check the adequate control of worker exposure

LEV system examiners need equipment such as Pitot tubes, smoke generator, dust lamp, anemometer and sometimes air sampling kit.

LEV Hood Label

This is a new requirement under the HSG 258 that the examiner should attach a test label to each hood when tested and when the LEV requires remedy or repair, the examiner should instead attach a red “FAIL” label to the hood (see figure 2).  Employees who use the LEV system and their supervisors need this testing information.  All hoods (including fume cupboards) should carry a simple test label.  

Figure 2: Test label

Test Reports

The HSE has highlighted some issues for employers with current reports and these are:

1. Report goes to engineering function and join the long queue
2. Report filed and forgotten
3. No action taken

The HSE would like to see the directors and senior managers taking the lead in treating the report as an ‘audit’ on previous years’ checking, maintenance and actions on test results.

A suitable test record should contain the following:

1. Prioritised remedial actions (including any red labels)
2. The process and substance(s) controlled
3.  LEV diagram showing location and test points
4. LEV system condition (including photos, serial numbers, etc)
5. Qualitative and quantitative test methods used
6. Qualitative and quantitative test assessment records
7. Required and assessed LEV system performance compared
8. Comments on operator methods of working
9. Comments on system wear and tear
10. Date of next examination and test
11. Signature

LEV Instrumentation

Quite often, it is difficult to tell whether an LEV system is working properly or not.  Hazardous substances are not always visible to the naked eye and nor do they always have an odour.  

Users of LEV systems, particularly the operators at LEV hoods, should be able to tell that the hood airflow continues to be adequate to control exposure.  Good practice requires the periodic monitoring of performance for all hoods.  Generally speaking, new and modern fume cupboards are designed with a complex device to activate an alert if the airflow drops below pre-set trigger levels6.  

The HSG 258 encourages employers to install an airflow indicator at every hood because the operator needs some simple indication that the hood is working properly.  It becomes critical when the operator has to adjust a damper to get adequate airflow.  The airflow indicator must indicate simply and clearly when the airflow is adequate.  A simple manometer can be used and there are other indicators available on the market (see figure 3)  

Fig 3. Airflow Indicator


·  The new HSG 258 published by the HSE is part of a campaign to raise standards and the HSE will also be taking a tougher line on inspection of LEV systems.  Further information on the new publications is available from the HSE website at:
·  If LEV is properly selected, installed, maintained and used, it can be an effective control measure, which reduces personal exposure to hazardous substances.
·  The Employer has a legal duty for arranging the thorough examination and test of LEV systems on an annual basis by a competent person.
·  The Examiner should issue a simple label for every hood examined and tested.
· The users of LEV systems need to see that the system is working properly and thereby controlling exposure.  This can be demonstrated by using a simple airflow indicator on every hood.


1: Control of substances hazardous to health (5th edition).  The Control of Substances Hazardous to Health Regulations 2002 (as amended). Approved Code of Practice and Guidance L5 (5th edition) HSE Books 2005 ISBN 978 0 7176 2981 7
2: Health and safety statistics 2007/08, A National Statistics publication.  Also
3: Time to clear the air! A workers’ pocket guide to local exhaust ventilation (LEV) Pocket card INDG409 HSE Books 2008 ISBN 978 0 7176 6300 2
4: Controlling airborne contaminants at work: A guide to local exhaust ventilation (LEV) HSG 258 HSE Books 2008 ISBN 978 0 7176 6298 2
5: Management of health & safety at work, MHSW Regulations 1999.  Approved Code of Practice and Guidance L21 (2nd edition) HSE Books 2000 ISBN 978 0 7176 2488 1
6:  Fume Cupboards Safety and Performance Requirements.  British Standards Institution, BS EN 14175-2:2003



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