Silica dust and new OSHA Construction, General Industry standards

A key supplier to trades frequently exposed to concrete and cement dust, Bosch Power Tools engaged former Concrete Construction editor and Bomanite pattern stamped flatwork contractor Joe Nasvik in a discussion on the federal government’s revised threshold for crystalline silica levels in Construction and General Industry workplaces. The agency has set a compliance target this month for contractors bound by the Construction workplace rule, with General Industry employers to follow in June 2018.

Joe Nasvik

J. Nasvik: When the U.S. Department of Labor issued its ruling aimed at better protecting workers from respirable silica dust, no one was surprised. Compliance with the new rule went into effect June 23, 2017, and enforcement begins Sept. 23, 2017. The upgraded regulation substantially reduces the permissible exposure limits (PEL) for workers in the construction industry. The Department of Labor’s Occupational Safety and Health Administration (OSHA) will enforce a reduction in the amount of silica that workers can be exposed to over an eight-hour day from 250 micrograms per cubic meter of air to 50 micrograms.

What exactly is silica? What kind is OSHA so concerned about?

Silicon (Si) is the second most common element on Earth, making up 28 percent of the planet’s crust. Oxygen is the most common element at 47 percent and aluminum is a distant third at 8 percent. Silicon combines with oxygen to form quartz (SiO2)—an example being sand. Silica is a component in a wide range of the Earth’s rock.

Is respirable crystalline silica a threat to life?

Inhalation of respirable crystalline silica is a threat to life. Particles can be created by natural forces such as wind, which causes them to collide and form smaller particles. According to OSHA, it’s estimated that 2.3 million U.S. workers are exposed to respirable silica dust at work each year.

But aren’t there already OSHA regulations in place to limit silica exposure?

OSHA set limits on respirable crystalline silica dust exposure in 1971, shortly after the agency was created. These regulations, based on research from the 1960s and earlier, soon showed that they didn’t adequately protect workers. The limits were imposed as formulas that many people found difficult to understand. The new rule limits the amount of silica dust that workers can be exposed to on the job to 50 μg/m3 averaged over an eight-hour shift for all covered industries. That’s about 1/20th the size of a grain of salt.

What should contractors and people on the jobsite do to avoid silica dust exposure?

Employers are required to use “engineering controls” such as vacuum dust collection or water-delivery systems to limit worker exposure to respirable silica dust and use respirators as required. Specified exposure control methods are referenced in OSHA Table 1, [which is] at the heart of the new silica dust control regulations for the construction industry.


Bosch Power Tools’ Pro+Guard dust solutions lineup provides options to assist companies and their workers in complying with new OSHA silica exposure thresholds. The focus is on developing better dust extractors and attachments, such as shrouds, to capture dust at the source. Bosch-engineered dust control solutions help users provide jobsite air quality that meets OSHA regulations.

How do I know what tools I need for the job I’m doing?

OSHA Table 1 matches common construction tasks with effective dust control methods. The table has three columns: the task or equipment being used, one describing the method for controlling dust and a third stating what type of respiratory protection is needed when performing the task. By finding a work activity on the table, it’s easy to determine what steps are necessary to ensure compliance.

Then what’s the alternative? What are manufacturers doing to help solve this?

The best way to control respirable crystalline silica dust is to remove it as it’s created. Power tool manufacturers have developed products and systems to help meet OSHA requirements for limiting silica dust exposure.

How are concrete workers supposed to capture dust so it doesn’t become airborne?

For most concrete applications, tool attachments that confine dust are connected to vacuums to prevent particles from becoming airborne. These systems represent a primary method for keeping the air clean. Attachments include shrouds for grinders and dust extraction attachments that fit around chipping hammer bits and hammer drill bits.

Another component specifically for drilling concrete are dust extraction bits. The bit allows dust created at the bottom of a hole being drilled to be sucked through the center of the bit and collected in the dust extractor.

So, I just connect these accessories to my regular vacuum in the shop?

No. The vacuum needs to have a high amount of CFM suction (+150), a filter cleaning feature built in and it is ideal for them to be HEPA compliant. To qualify as HEPA, U.S. government standards require that the air filter remove 99.97 percent of particles with a size of three microns or less. HEPA filters are expensive, but necessary for removing small particles. When looking for a HEPA vacuum filter that meets OSHA requirements, it must state on the filter that it will remove particles three microns in size or less. As a filter removes smaller and smaller particles, the power and airflow of the vacuum, as measured in cubic feet per minute (cfm), must increase.

How do you clean these specialty filters to make sure the vacuum still functions properly?

OSHA requires vacuum filters to function properly at all times. For vacuums intended for concrete/fine dust collection, certain vacs provide a feature that automatically cleans the filter every 15 seconds with reverse blasts of air (Bosch standard) to ensure the filter maintains its utility. Other manufacturers employ different filter-cleaning methods. Filters should never be washed out, especially when concrete dust is involved because it will harden in the pores and render the filter useless.


Bosch Speed Clean bits are built around an internal dust channel that’s milled to deliver dust reduction in a lightweight concrete bit. These bits are both OSHA and code approved for use with epoxy anchors. In addition, employers must create processes that minimize release of respirable silica dust into the environment during maintenance of tools and employee change of work clothes.