How OSHA regulates respirable crystalline silica in construction
Respirable crystalline silica is the fine dust released when you cut, grind, drill, or crush concrete, brick, block, stone, or mortar. Breathing it causes silicosis, lung cancer, COPD, and kidney disease. OSHA’s construction silica standard, 29 CFR 1926.1153, sets two numbers you measure exposure against, both as 8-hour time-weighted averages:
- Permissible Exposure Limit (PEL): 50 µg/m³. No worker may be exposed above this 8-hour TWA. 1926.1153(c)
- Action level: 25 µg/m³ (half the PEL). At or above this 8-hour TWA, the standard’s monitoring and medical-surveillance machinery is engaged. 1926.1153(b)
The standard gives you two compliance paths. You can follow Table 1 — a list of 18 common tasks with pre-engineered dust controls and respirator requirements (1926.1153(c)(1)) — and if you implement the specified controls fully and correctly for every task, you are not required to do air monitoring at all. Or you go the alternative exposure-control path (1926.1153(d)): assess each worker’s exposure with objective data or air sampling and keep them at or below the PEL.
How this calculator estimates the 8-hour TWA
OSHA doesn’t publish a single exposure number per task — real exposure depends on the material, the tool, water/ventilation, and work practices. Published NIOSH/OSHA datasets instead give a range. Because airborne respirable dust is well established to be roughly log-normal, the calculator uses the geometric mean of each task’s published uncontrolled range as the typical concentration, then time-weights it to a full shift:
- Central task concentration = √(low × high) of the published uncontrolled range (µg/m³).
- Contribution to the 8-hour TWA = concentration × (task hours ÷ 8) — only the hours spent on that task count, with zero exposure assumed for the rest of the shift.
- Combined TWA = the sum of every task’s contribution, compared to the 50 µg/m³ PEL.
This is the uncontrolled estimate — it deliberately does not apply a made-up “Table 1 reduction factor.” Under Table 1 you comply by implementing the specified controls and respirator, not by hitting a particular µg/m³ number. The estimate is for planning and prioritization; it never replaces the personal air monitoring required by 1926.1153(d).
Construction silica tasks, exposure ranges & Table 1 status
Uncontrolled 8-hour-equivalent concentration ranges are from published NIOSH/OSHA construction task data; the central value is the geometric mean used by the calculator. “Table 1 #” is the task’s entry in 1926.1153(c)(1) Table 1.
| Task | Uncontrolled range | Central (geo-mean) | Table 1 |
|---|---|---|---|
| Concrete Cutting (Handheld Saw) | 200–2000 µg/m³ | 632 µg/m³ | #2 |
| Concrete Cutting (Walk-Behind Saw) | 100–1200 µg/m³ | 346 µg/m³ | #4 |
| Masonry Saw (Stationary) | 150–1500 µg/m³ | 474 µg/m³ | #1 |
| Concrete Grinding / Surface Prep | 100–1500 µg/m³ | 387 µg/m³ | #12 |
| Tuck-Pointing / Mortar Removal | 500–5000 µg/m³ | 1581 µg/m³ | #11 |
| Jackhammering / Chipping | 100–600 µg/m³ | 245 µg/m³ | #10 |
| Drilling into Concrete (Handheld) | 50–500 µg/m³ | 158 µg/m³ | #7 |
| Dowel Drilling Rig | 80–400 µg/m³ | 179 µg/m³ | #8 |
| Sweeping Concrete Dust (Dry — PROHIBITED) | 100–2000 µg/m³ | 447 µg/m³ | Not on Table 1 |
| Heavy Equipment Demolition | 50–300 µg/m³ | 122 µg/m³ | #17 |
| Walk-Behind Milling / Floor Grinding | 100–800 µg/m³ | 283 µg/m³ | #13 |
| Crushing Machines | 50–400 µg/m³ | 141 µg/m³ | #16 |
A worker only has to exceed the 50 µg/m³ PEL for part of a shift to be over the limit on an 8-hour TWA basis — most of these tasks do, uncontrolled, in well under an hour.
Worked examples
1. Tuck-pointing, 4 hours. Mortar removal is the highest-exposure task on Table 1 (entry #11), with a published uncontrolled range of 500–5000 µg/m³. Geometric mean = √(500 × 5000) = 1581 µg/m³. Over 4 of 8 hours: 1581 µg/m³ × 4 ÷ 8 = 791 µg/m³ — about 15.8× the PEL. Because it’s on Table 1, you can comply by running the required shroud + dust collector (≥25 cfm per inch of wheel, 99%+ filter with a cleaning mechanism) and the specified respirator — no air monitoring required if implemented fully.
2. Grinding 4 h + drilling 4 h. Concrete grinding (geo-mean 387 µg/m³) for 4 hours contributes 194 µg/m³; handheld drilling (geo-mean 158 µg/m³) for 4 hours contributes 79 µg/m³. Combined 8-hour TWA ≈ 273 µg/m³ (5.5× the PEL). Both are on Table 1, so the Table 1 path is fully available — implement each task’s specified controls and you avoid monitoring.
What to do next
- Decide your path. If every task is on Table 1, follow the specified controls and respirator exactly and you skip monitoring. If any task isn’t, get objective data or sample the air per 1926.1153(d).
- Write the exposure control plan and name a competent person — 1926.1153(g). Review it at least annually.
- Offer medical surveillance to anyone required to use a respirator 30+ days/year (1926.1153(h)(1)(i)) — 1926.1153(h). It’s triggered by respirator use, not by the action level.
- Kill the dust at the source with water or HEPA vacuum dust collection. Dry sweeping and dry brushing are prohibited where wet methods or HEPA vacuuming are feasible — 1926.1153(f).
- Train each worker before the task and whenever conditions change — 1926.1153(i).
Frequently asked questions
What is the OSHA PEL for silica in construction?
The permissible exposure limit is 50 µg/m³ as an 8-hour TWA. The action level is 25 µg/m³ (half the PEL).
What is Table 1 and can I avoid air monitoring?
Table 1 (29 CFR 1926.1153) lists 18 common construction tasks with pre-approved controls. Following Table 1 exactly eliminates the need for exposure monitoring.
When is medical surveillance required?
In construction (29 CFR 1926.1153), medical surveillance must be offered to each employee who is required to wear a respirator for 30 or more days per year — it is triggered by respirator use, not by the action level. Initial exam within 30 days of assignment (unless one was done in the last 3 years), then at least every 3 years.
What are the penalties for silica violations?
Silica citations are typically classified as serious, with a maximum of $16,550 each (2026 amount, unchanged from 2025). Willful or repeated violations can reach $165,514. Inspections often result in multiple citations, but total exposure depends on the number and classification of violations and any size/good-faith/history reductions — there is no fixed "typical" total.
Is this calculator a substitute for air monitoring?
No. This tool provides estimates based on published exposure data. For legal compliance, you must either follow Table 1 exactly or conduct personal air monitoring per 1926.1153(d).
Sources & verification
- 29 CFR 1926.1153 — Respirable Crystalline Silica (construction), full text incl. Table 1
- OSHA — Crystalline Silica Rulemaking & construction guidance
- NIOSH — Silica topic page (task exposure data)
OSHA figures (PEL 50 µg/m³, action level 25 µg/m³, 29 CFR 1926.1153) verified 2026-10-05 against the cited primary sources. This calculator is an estimate for planning only — it is not air monitoring, not a prediction of any specific sampling result, and not legal advice.
Silica Table 1 control selector →Respiratory protection program builder →Noise exposure calculator →The 1926.1153 standard explained →Table 1 task-by-task guide →2026 silica compliance guide →
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