Guides
Silica on site: control the dust
By Claude Piché, founder · Updated September 18, 2026
Sawing, grinding, drilling, and demolition raise dust. Field method: control at the source before relying on a mask. Articles and exceptions live on the CSTC 3.25 sheet.
Do not redo the legal sheet here
Which materials are presumed to contain silica, when a respirator is required, and the ban on dry sweeping: those are CSTC 3.25 thresholds on the regulation page. This guide is how to organise on the pile.
In an establishment, other rules (RSST, CSA Z94.4 program) may apply. On a construction site, start from CSTC 3.25.
Before you cut or drill
Name the task (concrete sawing, drilling, jackhammer) and the source control: water, HEPA vacuum, isolation, or confinement. Prepare the respirator for that task and check the fit. A sawing/drilling or masonry list covers pre-start items.
If someone claims the concrete “has no silica”, the proof belongs on the legal sheet (SDS / analysis). Do not assume it in the field.
During the work
Keep water or vacuum actually running — not only “available on the truck”. Limit who walks through the cloud. Stop if source control fails.
A mask does not erase a visible cloud. Control first, respirator second, as the 3.25 sheet describes.
Cleanup and close-out
No dry sweeping or compressed air in areas covered by 3.25.8 — details on the sheet. Vacuum, wet, bag waste. Record the task in a report if your program asks.
OK Sécurité is not a lab and does not measure OELs. For a demonstration under exposure limits, use industrial-hygiene competence.
Practical guide, not industrial-hygiene advice. Duties sit in CSTC 3.25 and, where applicable, the RSST. OK Sécurité is not certified by the CNESST. Read the regulation sheet and the official text. For information only — this is not legal advice. OK Sécurité is an independent company with no affiliation to the CNESST: we are not mandated, endorsed or certified by it. Where there is any discrepancy, the official text published by Légis Québec or the CNESST prevails.
Sources
Informational only. Confirm obligations with your prevention program and:
- CNESST — Mesures spécifiques pour les chantiers de construction
- Safety Code for the construction industry (CSTC) and Regulation respecting occupational health and safety (RSST)
Official rules (French)
Related checklists
Lists for dust-raising tasks:
Common questions
- Is an N95 enough to saw concrete?
- Do not treat that as a default yes. The CSTC 3.25.6 sheet frames respirators for sawing, with exceptions (isolation / confinement or a demonstration under the OELs).
- Where are the exposure values?
- RSST Annex I, referenced by CSTC 3.25. This guide does not republish mg/m³. Read the crystalline-silica sheet and the official text.
- Does earthwork count?
- Rock, concrete, and materials on the 3.25.2 list can. Use the earthwork list and the legal sheet, not an invented “all soil = silica” rule.
- Does OK Sécurité certify silica-free material?
- No. The app helps tick field controls. An SDS or analysis is a different document.