Tile (C-54) · Lesson 7 of 7

Cutting Tile Safely: Silica Limits, Wet Cutting, and the 8-Hour TWA

"Cutting Tile Safely: Silica Limits, Wet Cutting, and the 8-Hour TWA" is lesson 7 of 7 in the Tile (C-54) Learning Hub. It opens with "Why Tile Cutting Is a Silica Job" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. Why Tile Cutting Is a Silica Job
  2. The Two Numbers: PEL 50 and Action Level 25
  3. Table 1: The Specified Controls
  4. Calculating an 8-Hour TWA
  5. What the Result Triggers and Housekeeping

The worked example in the course applies this lesson to a realistic job in 5 steps, from "Multiply each concentration by its hours" through "Pick the control".

What you'll be able to do

  • Explain the main idea of "Cutting Tile Safely: Silica Limits, Wet Cutting, and the 8-Hour TWA" in plain language you can use on the exam.
  • Apply this step with confidence: "Table 1: The Specified Controls".
  • Apply this step with confidence: "Calculating an 8-Hour TWA".
  • Apply this step with confidence: "What the Result Triggers and Housekeeping".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Silica Exposure: The 8-Hour TWA CheckRespirable silica dust, µg/m³PEL 50TWA 40AL 253 h at 905 h at 10Dry cutting,handheld sawOther tasks8-HOUR TWATWA = sum(conc x hrs) / 8= (3 x 90 + 5 x 10) / 8= (270 + 50) / 8= 40 µg/m³Action level (AL): 25PEL: 5025 to 50: above the AL,under the PELRe-monitor within 6 monthsFix it at the source: a saw with water continuously fed to the blade(a stationary masonry saw, Table 1 item (i)) lists no respirator.Handheld power saw: indoors APF 10 respirator at any duration; outdoors only over 4 h per shift.Source: Cal/OSHA 8 CCR 1532.3: AL (b), PEL (d)(1), Table 1 (c)(1), monitoring (d)(2)(C)Concentrations are example values; TWA = sum of (concentration x hours) divided by 8CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Why Tile Cutting Is a Silica Job

Porcelain, ceramic, stone, cement board, mortar beds, and grout contain crystalline silica. Cutting, grinding, or chipping them throws off respirable silica dust that can cause silicosis and lung cancer, and the dust builds up over years. California regulates it under Cal/OSHA Title 8 section 1532.3 (Occupational Exposures to Respirable Crystalline Silica) in the Construction Safety Orders. Subsection (a) applies the section to all construction exposures except where exposure will remain below 25 micrograms per cubic meter as an 8-hour TWA under any foreseeable conditions.

Step 2: The Two Numbers: PEL 50 and Action Level 25

The action level is defined in 8 CCR 1532.3(b) as 25 micrograms per cubic meter of respirable crystalline silica, calculated as an 8-hour time-weighted average (TWA). Under 8 CCR 1532.3(d)(1), the employer shall ensure no employee is exposed to more than 50 micrograms per cubic meter as an 8-hour TWA; that is the permissible exposure limit (PEL), twice the action level. Subsection (d) is the route for tasks not on Table 1 or where Table 1 is not fully and properly implemented, and under (d)(2)(A) the employer must assess the exposure of each employee who may be at or above the action level.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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