• Key definitions for silica (construction) may be found in this section.

Action level: A concentration of airborne respirable crystalline silica of 25 μg/m3, calculated as an eight-hour time-weighted average (TWA).

Competent person: An individual who is capable of identifying existing and foreseeable respirable crystalline silica hazards in the workplace and who has authorization to take prompt corrective measures to eliminate or minimize them. The competent person must have the knowledge and ability necessary to fulfill the responsibilities set forth in 1926.1153(g).

Employee exposure: The exposure to airborne respirable crystalline silica that would occur if the employee were not using a respirator.

Physician or other licensed health care professional: An individual whose legally permitted scope of practice (i.e., license, registration, or certification) allows them to independently provide or be delegated the responsibility to provide some or all of the particular health care services required by 1926.1153(h).

Respirable crystalline silica: Quartz, cristobalite, and/or tridymite contained in airborne particles that are determined to be respirable by a sampling device designed to meet the characteristics for respirable-particle-size-selective samplers specified in the International Organization for Standardization (ISO) 7708:1995: Air Quality—Particle Size Fraction Definitions for Health-Related Sampling.