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):

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:

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 http://www.hse.gov.uk/lev/index.htm)  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 24^th 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 documents^3,4 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:

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

Thorough examination and testing of LEV system involves three stages:

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:

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:

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

Conclusions

References.