As you are legally responsible to ensure that exposure to dust & fumes for your workforce is minimised and controlled, you need to ensure that your lev company is reputable.
You should look for references or testimonials of your Local Exhaust Ventilation testing company. HSG258 says that a “competent person” should carry out the tests. We strongly feel that this person should be P601 accredited. This is a UK qualification on Thorough Examination and Testing of Local Exhaust Ventilation Systems. The company you choose should be able to demonstrate an understanding of the law & of the COSHH regulations & Approved Code of Practice.
What should the LEV testing company do?
An LEV tester will check the airflows of the ducts, check face velocities of hoods, perform smoke tests to find the maximum capture distance, perform visual inspection of the filters and system in general, and investigate the processes being used to determine if the system is used correctly.
All of this information and more will be compiled into a comprehensive LEV report, which you should keep on record for a minimum of five years.
In the event of a system being deemed unsatisfactory, a good LEV engineer will advise you of the necessary steps that need to be taken to return it to an acceptable condition.