Air quality and particle presence remain significant hazards in the Australian workplace. From high-rise construction sites to underground mining operations and DIY projects around the home, particulate matter is an ever-present threat to health. In response, Local Exhaust Ventilation (LEV) – or Local Area Ventilation (LAV) – manages the risks while allowing essential work to progress in relative safety. When used alongside other control or elimination measures, LEV is a powerful tool to minimise the health hazards to people. Also called mechanical extract ventilation, LEV allows air and its captive particles to be removed from the immediate area, filtered, and discharged back into the atmosphere. This is achieved with a hood, a fan, ducting and filter element, which can be customised to suit the particular work environments and known contaminants. While the process itself is straightforward, moving air from a to b, the calculations that go into preparing an LEV method are not.

Multiple factors must be considered to design the right LEV system, including:

  • Molecular weight
  • Air temperature
  • Vapour pressure
  • Flow volume
  • Concentration
  • Local regulations

By following the guidelines and using available resources to design an LEV, companies can ensure that their worksites benefit from maximum contaminant protection. Without an LEV, contaminants are free to travel around in the air and be inhaled by the people present. The inhalation of airborne contaminants is associated with multiple chronic diseases, including silicosis and coal workers’ pneumoconiosis or black lung.

The correct implementation of an LEV is vital and is broken down into specialties, including:

Designers: Required to interpret customer needs and provide effective LEV systems capable of delivering the required control

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Installers: To assemble and locate the LEV equipment, commission it and ensure it adequately controls contaminant exposure

Examiners: Needed to detect and remedy system defects and ensure that LEV systems continue to deliver effective control.

When to Use Local Area Ventilation (and when to not)

LAV is not a substitute for the complete removal of a hazard. The first port of call and at the top of the risk matrix hierarchy, elimination should always be investigated when working in a dangerous area.

While able to capture contaminants at their source, mechanical ventilation remains a small-scale solution for use in clearly identified areas and only moves a fraction of the air compared to general ventilation. 

A quick checklist can identify if LAV is suitable for your workspace, including:

  • Whether a contaminant is harmful, toxic or corrosive, like lead fumes, acid mist or solvent vapour
  • If contaminant levels are high in the zone
  • Regulations state contaminants must be removed before release into the air 
  • Also, if the process gives off significant heat.

Regulations lie at the heart of the issues and dictate when LAV should be considered. Australian Occupational Safety and Health Regulations stipulate that, as far as practicable: “Employers must reduce the risks from hazardous substances. The regulation also requires that control measures such as ventilation be used in preference to personal protective equipment where practicable. ”Under the Act, an employer must ensure that employees are not exposed to workplace safety and health hazards while providing adequate information, instruction and training. Employers must also consult with “safety and health representatives and other employees about workplace issues, and where exposure to hazards can’t be eliminated, provide employees with adequate personal protective clothing and equipment.”  While it’s easy to get lost in the rules and regulations, the fact remains that LAV is an important and essential measure in minimising risk at work.

Assembling and Testing Your LEV System

As an engineering control measure, you must choose the components of your system for maximum effect. The flip side is a process that’s ineffective at removing contaminants, and that’s a problem, mainly if those working think the area is safe and forgo masks, etc. Once installed and checked that it’s working correctly, an LEV must also be tested regularly, per regulations.

The components of an exhaust system are often consistent and can include:

  1. The Hood

To capture the most contaminated air, a hood should be as close to the source of contamination as possible or enclose the body of air – like a spray booth, for example. The hood must also be chosen for either dust or fume capture.

      2. The Ducting

Ducting should allow the contaminated air to travel through the systems and the air cleaner element. It’s best to avoid sharp corners in your ducting and keep it easy to access for assessment, maintenance and cleaning. Regular inspections are vital as ducting systems have been known to collapse under the weight of collected dust or to catch fire thanks to dust buildup.

     3. The Air Cleaner

An air cleaner or filter element removes particles from the air. Air cleaners must be selected to match the contaminant while being easily cleaned or replaced without further exposure. Filter elements must also be cleaned to ensure they continue working effectively.

    4. The Fan

The fan moves air through the hood and ducts it to the exhaust stack. An occupational hygienist or industrial ventilation engineer will help you choose the correct type and fan size for your LEV system, ensuring it operates effectively. The fan should be positioned for easy maintenance and to minimise the noise hazard for nearby workers.

    5. The Exhaust Stack

An exhaust stack discharges contaminated air to the outside world. Exhaust stacks should not discharge into a public area or near air inlets for air-conditioners or neighbouring buildings. They must also be checked for correct air volume, leaks, and corrosion while running.

 

Dust suppression is a critical issue in the world of mining and resources.

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References:

https://www.hse.gov.uk/lev/index.htm

https://www.commerce.wa.gov.au/worksafe/local-exhaust-ventilation

https://www.worksafe.govt.nz/topic-and-industry/fumes/local-exhaust-ventilation-quick-guide/