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Course 851 - Silica Dust Safety in Construction

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The Basics

In order to discuss the various aspects of welding, cutting and brazing safety, first we need to cover the basics in this first module. So let's get started.

Silica is more than just dust

Silica dust can be generated at dangerous levels anytime materials such as ceramics, concrete, masonry, rock and sand are mixed, blasted, chipped, cut, crushed, drilled, dumped, ground, mixed or driven upon.

Employees at construction sites may be exposed to silica dust during general housekeeping activities such as sweeping, emptying vacuum cleaners, and using compressed air for cleaning.

Silica exposures may also occur whenever silica-containing dust is disturbed, such as during material handling. The small particles generated during these activities easily become suspended in the air and, when inhaled, penetrate deep into employees’ lungs.



Quartz is the most common form of crystalline silica. In fact, it is the second most common surface material accounting for almost 12% by volume of the earth’s crust. Quartz is present in many materials in the construction industry, such as brick and mortar, concrete, slate, dimensional stone (granite, sandstone), stone aggregate, tile, and sand used for blasting. Other construction materials that contain crystalline silica are asphalt filler, roofing granules, plastic composites, soils, and to a lesser extent, some wallboard joint compounds, paint, plaster, caulking and putty.

Cristobalite and Tridymite

Cristobalite and tridymite are natural constituents of some volcanic rock. Man-made forms result from conversion of quartz or amorphous silica that has been subjected to high temperature or pressure. Diatomaceous earth, composed of amorphous silica, crystallizes during heating (calcining), yielding a calcined product that contains as much as 75% cristobalite. Cristobalite is also found in the superficial layers of refractory brick that have repeatedly been subjected to contact with molten metal.

Visible and Respirable Dust


Visible dust contains large particles that are easy to see.

Respirable dust particles pose the greatest risk because they are not visible. They are are so small they can get deep into the lungs.

When exposed to silica dust, it’s important to remember the following:

  • Most dust-generating construction activities produce a mixture of visible and respirable particles.
  • You should use visible dust as a general guide for improving dust suppression efforts. If you see visible dust being generated, emissions of respirable silica are probably too high.
  • Methods that control tool-generated dust at the source can reduce all types of particle emissions, including respirable particles.
  • Do not rely only on visible dust to assess the extent of the silica hazard. There may be more airborne respirable dust present that is not visible to the naked eye.

Written Exposure Control Plan (ECP)

The first step, and a very important OSHA requirement, in making sure exposure to silica dust is controlled is to design, development, and deploy an effective Exposure Control Plan (ECP).

  • The components of an effective ECP should include at least the following elements:
  • A description of the tasks in the workplace that involve exposure to respirable crystalline silica;
  • A description of the engineering controls, work practices, and respiratory protection used to limit employee exposure to respirable crystalline silica for each task;
  • A description of the housekeeping measures used to limit employee exposure to respirable crystalline silica; and
  • A description of the procedures used to restrict access to work areas, when necessary, to minimize the number of employees exposed to respirable crystalline silica and their level of exposure, including exposures generated by other employers or sole proprietors.
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    • The employer should review and evaluate the effectiveness of the written exposure control plan at least annually and update it as necessary.
    • The employer should make the written exposure control plan readily available to each employee and their designated representatives.
    • The employer should designate a competent person to make frequent and regular inspections of job sites, materials, and equipment to implement the written exposure control plan.

ECP Evaluation

It is important to conduct regular inspections in general industry workplaces and construction worksites for silica dust exposures, and evaluations of the ECP. To help ensure an effective ECP and positive OSHA enforcement inspections, be sure to check and evaluate the areas in the checklist to the right.


Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. Silica dust may be generated anytime masonry or rock are _____.

2. What is the most common form of silica?

3. What indicates that the level of respirable silica is probably too high?

4. What is the first step, and a very important OSHA requirement, in making sure exposure to silica dust is controlled?

5. Who should make frequent and regular inspections under the exposure control program (ECP)?

Have a great day!

Important! You will receive an "error" message unless all questions are answered.