Control of Substances Hazardous to Health 2004

Local Exhaust Ventilation Plant (LEV)

The Regulations apply to all work activities where substances, which are potentially hazardous to health, are used or produced.

They were originally implemented in 1988, enforceable from 1989 and replace some fifty sets of previous legislation relating to specific industries and processes, with a flexible and all embracing approach to all work activities involving hazardous substances.

They have been revised on numerous occasions. However, the section of the Regulations concerning LEV in the workplace have remained unchanged.

Asbestos, lead, materials producing ionising radiation and substances below ground in mines are excluded from the Regulations as they are already adequately covered by existing legislation. Also excluded are substances hazardous solely due to their flammability or explosive nature or because they are kept at high or low temperatures of high pressure.

In essence, previous legislation has been embodied into the COSHH Regulations with certain additions, resulting in the requirement for all LEV, in a workplace controlling fumes vapours gases or dusts from processes, to be thoroughly examined and tested periodically. These periods vary from one month to six months and finally fourteen months dependent upon the process and usage.


The basic requirement of the Regulations is that employers must assess the likelihood of risk to the health of their employees and others from exposure to hazardous substances arising from work activities

The Regulations state that following 1st January 1990 no work, which is liable to expose anyone to substances hazardous to health, shall be carried on unless an assessment has been made..

Except in all but the minor circumstances, it is envisaged that the assessment process will need to be documented to prove the methodology.

The responsibility for undertaking an assessment lies with the employer and cannot be delegated. However, this does not preclude the use of personnel both from inside and outside the organisation. Indeed, where air-sampling or biological monitoring is necessary for the assessment, recourse to outside specialists may be unavoidable.

Control Measures

Having assessed what substances likely to be hazardous to health are present, where they are present and risk of exposure to that hazard exists, the next stage required by the Regulations is the prevention or adequate control of that exposure.

Engineering controls are provided to control exposure, and LEV is a control strategy which figures prominently in the legislation.

In all cases, engineering control measures provided to control exposure must be thoroughly examined and tested at specified intervals. This is to ensure that the control measures are still performing as originally intended.

The results of each thorough examination and test should be checked against the assessment carried out under Regulation 6 and the requirements of Regulation 7 regarding control.

Where an initial assessment or the manufacturer’s intended operating parameters are not available, then the system will require an appraisal in accordance with Regulation 6 to show compliance with Regulation 7. 

The HSB Service

The Health & Safety Executive are actively policing the Regulations and prosecutions in the courts are being pursued along with the issue of prohibition/improvement notices.

The HSE have recently published HSG258 “Controlling airborne containments at Work”. This publication replaces the previous documents HSG37 and HSG54. It contains comprehensive advice to owners of LEV systems as well as prescribing what competent organisations must carry out when either Commissioning, Maintaining or undertaking periodic Thorough Examination of such systems.

Liability Insurers are insisting on compliance with the Regulations before renewing or incepting Employers Liability insurance's in some trades/industries. HSB have fully trained and qualified engineers in place throughout the country to:

  1. Carry out initial appraisals with laboratory analysis of samples.
  2. Carry out period examinations of LEV plant to prove the plant is still operating effectively.