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Reduce Exposure to Silica Dust

Posted on September 7, 2011

As featured on ConcreteConstruction.net

Earlier this year, the Occupational Safety and Health Administration (OSHA) issued their annual spring regulatory agenda, which outlines the agency’s top priorities over the next few months. Among the worker safety issues that OSHA is focusing on in the short term is developing a proposed rule for Occupational Exposure to Crystalline Silica.

Crystalline Silica, often referred to as just “silica,” is a mineral found in the earth’s crust, primarily in the form of quartz. According to OSHA, it is an important industrial material usually found in sand, stone, concrete, brick and mortar that has long been known to pose serious health risks when respirable particles are inhaled, primarily resulting in the deadly lung disease, silicosis. It is estimated that nearly 2 million workers are exposed to silica in a variety of industrial settings, including mining, manufacturing, construction, maritime, and agriculture. These industries frequently generate silica dust through their sawing, drilling, crushing and sand blasting processes.

While OSHA navigates the rulemaking process that will one day result in a final rule that will set guidelines and recommendations for keeping silica levels at a minimum, the agency currently has an established Permissible Exposure Limit (PEL), which is the maximum amount of crystalline silica workers may be exposed to during an 8-hour shift, (defined in OSHA’s standard 29 CFR 1926.55 and 1910.1000).  In 2008, OSHA issued a National Emphasis Program (NEP) for crystalline silica exposure to identify, reduce, and eliminate health hazards associated with occupational exposures.

The NEP outlines safety and prevention procedures that facilities should implement properly in order to keep their PEL below the legal limit and avoid hefty citations. These procedures include: employee exposure monitoring, engineering and work process controls, respiratory protection, hazard communication, abrasive blasting, and also housekeeping and hygiene practices. While all prevention practices are important, housekeeping plays a critical role due to its ability to keep dust levels at a minimum throughout the manufacturing process.

While there are several housekeeping methods to minimize silica dust in the workplace, HEPA filter industrial vacuum cleaners are often preferred since they can completely collect and retain silica dust without dispersing it back into the environment. Methods like compressed air blow-downs and dry sweeping are discouraged since they create dust clouds and only transfer dust particulate from one area to another.

Aside from general cleaning to remove dust accumulations on exposed surfaces, HEPA industrial vacuum cleaners can be used in various other ways to keep silica exposure limits to a minimum.

Use of vacuums with power tools

Many manufacturers, such as those in the concrete and construction industry, have eliminated silica dust exposure at the source by using vacuum assisted power tools that are used in conjunction with HEPA filter industrial vacuum cleaners.  In this set-up, the vacuum hose is integrated into the power tool to quickly and easily suck up dust and debris while the operator is simultaneously drilling or sanding. 

Overhead and hard-to-reach areas

Equipped with the right hose and accessories, industrial vacuum cleaners can be used to easily accomplish difficult cleaning challenges, such as removing dust accumulations from overhead pipes and beams and accessing other hard- to-reach areas. Out of sight does not mean out of mind and cleaning these areas are just as important as visible areas, since dust accumulations also present other worker safety risks in the form of combustible dust fires and explosions.

Decontaminate worker clothes

OSHA recommends that worker clothes and uniforms be cleaned frequently to prevent the transfer of silica dust from work areas to break rooms, other parts of the facility, and most importantly into the home. Industrial vacuum cleaners are an easy to way to remove excess silica debris from clothes and uniforms, and many facilities position portable industrial vacuum units at the exits of silica work areas, so workers can decontaminate their clothes before leaving.

Not all HEPA vacuums are created equal

From portable and stationary, to intermittent-duty and continuous-duty, to electric and air-operated, industrial vacuum cleaners are available in many different models, depending on the need and requirements of the facility. While these decisions often come down to personal preference, there are several elements to choosing an industrial vacuum cleaner for silica control that are important.

When it comes to collecting dust that is often very fine in composition like silica, a multi-stage, graduated filtration system for peak operating efficiency is extremely important. A graduated filtration system uses a series of progressively finer filters to trap and retain particles as they move through the vacuum. The largest particles are captured first by coarser filters; smaller particles are then caught and retained by the finer HEPA filter(s). This multi-stage system protects the HEPA filters from blockage and excessive wear-and-tear and maintains peak performance.

In addition, the filtration system should use oversized filters, which slow airflow across the larger surface area and optimize the air-to-cloth ratio. This allows the vacuum to easily collect large volumes of debris over extended periods of time with minimal maintenance.

Perhaps most important, the HEPA filter, which should at a minimum retain 99.97% of particles down to and including 0.3 microns, must be the last stage of filtration. This ensures that the vacuum’s exhaust air is completely filtered to prevent minute silica particles from passing through the vacuum and back into the environment.


As OSHA progresses through the rulemaking process, the agency is actively inspecting facilities and citing them for violations associated with silica dust. Recent citations have been for hazards that are easily preventable through proper housekeeping, such as overexposing employees to breathable crystalline silica while sandblasting, lack of engineering controls to keep silica exposures below the permissible limit, not running exhaust through a dust collection system, and allowing dust to accumulate outside the blast enclosure.  A HEPA filter industrial vacuum cleaner can be customized to meet all of these demands, and manufacturers should view the addition of a quality HEPA vacuum as an investment that will keep workers safe and companies out of OSHA’s target. For more information on crystalline silica in the workplace, visit OSHA’s silica Safety and Health Topic site at www.osha.gov/dsg/topics/silicacrystalline/index.html.