If you work in an industry where dust is produced, you are probably already aware of what a local exhaust ventilation system is. For those who don’t, a LEV is a control system designed to reduce exposure to contaminants and pollutants in the air. These could include mist, dust, fumes, gas or vapours. You will of course first need to idenitfy the areas in which dust and other particles are an issue. A Dust Monitor like the ones you can see at http://www.mattsmonitors.co.uk/construction-dust-monitors.html can help give you this information. Then you can apply your LEV system.
Most systems will consist of a hood, which is where the pollutant enters the system. Ducting is the system whereby pollutants travel via conducted air to a point of discharge. An air cleaner acts as a filter to clean the extracted air. Not all ventilation will need to have the air cleaning process. The mechanism that moves the air is usually in the form of a fan that discharges the air into a safe place. LEV systems require regular maintenance and component checks to ensure the contaminants are being effectively removed from the work environment.
Air pollutants come in many different forms such as vapours, gases, dusts, mists and fumes. They are particles and each type will have different properties. The size of the particles determines whether they are inhalable or respirable. This means some are big enough to be inhaled into the upper respiratory system and usually cleared through coughing or sneezing or will simply fall onto floors and surfaces due to their weight. The risk from respirable particles comes because they are tiny, fine particles that are not visible to the naked eye and are breathed deeply into the lungs where damage is caused.
When it comes to dust particles, what you can see is not always necessarily what’s there in the atmosphere. A cloud that contains respirable particles is virtually undetectable by the naked eye. Clouds that are visible normally fall under the inhalable category. When mist or fumes are generated, these tend to be more visible than the equivalent amount of dust.
The dust from processing organic material like flour or wood are mostly inhalable, whilst dust produced from minerals like concrete and stone fall under the respirable category.
Whilst LEVs are the most effective method of controlling exposure to airborne pollutants, there is more to controlling the risk than simply buying and installing the right equipment. A combined approach is required, including both engineered solutions, such as LEV, and good work practices in methods and procedures.
Every piece of equipment should contain alerts and features to control polluting clouds. As well as LEV, this might also include screens, handling machinery, jigs and any elements with a design purpose. Take for example, the joining seals on an enclosed conveyor. These can also be an important area for reducing exposure and emissions.