851 Silica Dust Safety in Construction

Alternative Exposure Control Methods

Under OSHA's silica dust rule for construction (29 CFR 1926.1153), there are specific tasks listed in Table 1 that allow employers to follow a clear set of dust control methods instead of measuring workers' exposure. However, when:

• A task is not listed in Table 1, or
• The employer does not follow all required engineering controls, work practices, and respiratory protection in Table 1

The employer must use alternative exposure control methods. These methods involve measuring workers' exposure to respirable crystalline silica and ensuring it stays below OSHA’s permissible limits.

Permissible Exposure Limit (PEL)

The employer must ensure that no worker is exposed to more than 50 micrograms per cubic meter of air (50 µg/m³), calculated as an 8-hour Time Weighted Average (TWA). This means the average amount of silica dust in the air that a worker breathes over a full 8-hour shift must be at or below this limit.

Example: If a worker operates a handheld grinder on concrete for 4 hours, and performs non-silica tasks the rest of the day, the employer must calculate the average silica dust exposure across the full shift. If the average exposure is above 50 µg/m³, corrective actions are required.

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