LEV is an engineering system that captures contaminated air (dusts, vapours, fumes) at their source and transports them away from the worker’s breathing zone. This prevents workers from inhaling the contaminant and reduces contamination of the general workplace air.
Selecting the right LEV system
Making sure that you choose the right LEV system for your workplace can be complicated. Poor design, installation and maintenance of any one component will reduce the ability of the system as a whole to capture and contain the contaminated air. LEV systems should be designed by an industrial ventilation engineer/supplier who has assessed the ventilation needs of the workplace.
The ducting system carries the contaminated air away from the work area.
The air cleaner filters and cleans the air before it’s released (outside, away from air intakes).
The fan must generate sufficient airflow to achieve a capture velocity that draws the contaminant away from the worker’s breathing zone. The fan draws the contaminated air though the hood and ducting to the exhaust stack.
The exhaust stack discharges the clean air to the outside.
Apply the hierarchy of controls
If you have identified contaminated air as a hazard, you must put control measures in place to manage employee exposure. The hierarchy of controls is a system that will guide you to select appropriate controls. The system sets out control measures in the order that they are best considered (you should take all practical steps to eliminate a hazard before working your way down the hierarchy). In many cases you can apply a combination of control measures, for example, installing LEV to remove the contaminated air and providing employees with respiratory protective equipment (RPE) to prevent them from breathing any remaining contaminants.
Risk assessment – what to consider when selecting LEV as a control measure
§ Which work processes create localised dusts, vapours and fumes?
§ What substances are being released into the air, what are the risks associated with them? Detailed information can be found on Safety Data Sheets.
§ How concentrated are the contaminants in the air?
§ What are the relevant workplace exposure standards?
§ Where is the process causing the contamination located (inside, outside or in a confined space)? Work in confined space requires further control measures.
§ Who is exposed to the hazard and for how long?
What to expect from your LEV supplier
Make sure that the supplier you chose is competent, ask about their professional qualifications, experience and industry membership.
Once the LEV is installed and commissioned your supplier should provide:
§ training for employees on how to use, check and maintain the system
§ a user manual and logbook
§ maintenance and replacement schedules
§ a list of consumable parts (including order numbers).
Looking after the LEV
Some basic checks will need to be performed daily or before use.
§ Checks and maintenance should cover:
§ moving parts that wear out such as fan bearings
§ non moving parts such as hoods, ducts and seals
§ replaceable/consumable parts such as filters.
§ Any defects must be reported to supervisors and faults fixed immediately to ensure the system continues to operate effectively.
§ Keep records of the checks and maintenance completed.
§ Have the system serviced by an industrial ventilation engineer annually.
Making changes to the system
§ Fitting additional hoods to an LEV system will reduce the effectiveness of the fan and the capture velocity at the hoods. A stronger fan may be required to ensure the system continues to operate effectively. An industrial ventilation engineer should review any proposed changes or additions to the system.
Using LEV with other control measures
§ The LEV system won’t necessarily capture all of the contaminated air, so other control measures may be required to protect employees. Installing LEV will usually reduce the grade of RPE needed. You should conduct further exposure monitoring to determine whether RPE is needed. Personal exposure monitoring should be completed following any modifications to the LEV system or other change to the process
§ One of the common reasons LEV systems are ineffective is because the hood doesn’t capture and contain the contaminated air. There are several different designs of LEV hood that are used for different processes.
§ Enclosing hoods are an effective type of hood because the contaminated air is completely contained. A glove box encloses the process, protecting the operator and preventing the contaminant from entering the workplace. Spray booths enclose the process and the operator, the contaminated air is contained but further controls such as personal protective equipment (PPE) are needed to protect the operator.