According to the COSHH Regulations, employers have a responsibility to ensure that employees are not exposed to substances hazardous to health and to take adequate measures to control such exposure.

The precautions taken should be adapted to local conditions. Arrangements should be made to evaluate whether the precautions taken were adequate, especially if circumstances of use change or new technology is introduced. If static eliminators are used in poorly ventilated rooms for an extended period of time, ozone can build up above the workplace exposure limit (WEL).

Prevention of Exposure

The goal should be to prevent or substantially reduce the release of ozone into the workplace. In many processes, destruction at the source is the most cost-effective way to reduce the release of ozone. It is recommended to use the protective equipment when dealing with ozone treatment process.

Control Measures

It should be possible to control the process using engineering controls, to the extent reasonably practicable. It is important to consider additional controls, such as improved work systems and respiratory protective equipment, in cases where these do not suffice. Whatever control measures are chosen, it is essential to make sure they are effective.

Engineering Control

Each workplace will require different engineering controls. The following methods will address the majority of situations:

■ Using local exhaust ventilation (LEV) near the source of ozone can be practical in some instances where the source can be identified. Extracted air can be passed through a filter to remove any ozone before discharging it, so that no more ozone enters the workroom air.

■ Whenever it is not reasonably practicable to use LEV or where the source of ozone is less defined, adequate general ventilation should be provided in the workroom.

■ When ozone is generated in a plant room, it is important that adequate ventilation be provided in order to rapidly disperse any danger-causing gases.

■ Gases that are designed specifically to reduce ozone levels are widely available, and are preferable to other shielding gases for use in arc welding. Visit the HSE welding webpage for more information on controlling welding gas and fume exposure

Respiratory Protective Equipment (RPE)


The use of protective equipment in combination with other controls is a valid strategy where other controls are not feasible or do not achieve adequate control. It is likely that RPE will be needed when confronting an ozone leak from a generator, or when performing inert gas shrouded welding operations on a production line.

Employees should be properly trained in using RPE, fit tested for tight-fitting respirators, and supervised. Selecting RPE suitable for the user and the environment should be determined, and it should be manufactured to an appropriate standard. In order for RPE to remain effective, it must be stored and cleaned appropriately. General information regarding the selection and use of RPE is available in the this document.

Maintenance, Examination & Testing of the Control Measures

Regulation 9 of COSHH requires that you ensure the following:

■ In order to prevent exposure to ozone, all equipment and plant must be in good working order, free of apparent defects, clean and in an efficient state of maintenance (the manufacturer/supplier of the plant can provide you with relevant information);

 ■ A review of the work safety systems, supervisory methods, and any other control measures is carried out at appropriate intervals;

■ Ensure the plant and equipment are properly maintained by performing frequent visual checks and conducting periodic thorough examinations by competent personnel.