Log entry 07 — Dust, slurry & silica safety
Wet cutting is not a preference. It is the control the law is built on.
Concrete dust carries respirable crystalline silica. OSHA's construction standard — 29 CFR 1926.1153 — sets a permissible exposure limit of 50 micrograms per cubic meter averaged over 8 hours, and its Table 1 prescribes the controls for each cutting task. For saws and drills, the prescribed control is water, delivered at the blade or bit, plus housekeeping and respiratory rules that follow from the task and duration. This page logs what that looks like on a real Littleton job.
The standard, translated to the slab
| Task | Table 1 control (summary) | Respirator, per Table 1 |
|---|---|---|
| Walk-behind / masonry saws, wet | Integrated water delivery at the blade, flow sufficient to suppress visible dust | None required at or under 4 hrs; APF 10 beyond 4 hrs for some saw classes — the operator's plan governs |
| Handheld saws, wet | Water at the blade, continuous spray | Per duration in Table 1; indoor work adds ventilation to prevent dust build-up |
| Core drills (rig-mounted or handheld), wet | Water feed through the drill / at the bit, slurry captured | None required when wet methods are used as specified |
| Dry work (rare, specified cases) | HEPA vacuum shroud systems, enclosed cabs, or ventilation as Table 1 states for that task | Required at levels Table 1 assigns; a dust mask by habit is not a program |
| Mixing, demolition, cleanup | Wet methods or HEPA vacuums; no dry sweeping, no dry compressed-air blowing where it exposes workers | Per task and duration |
Summary only — the standard itself governs. Employers must also maintain a written exposure control plan, designate a competent person, train workers, and handle medical surveillance and recordkeeping the rule requires. Homeowners hiring cutting work can reasonably ask two questions: “Wet or dry?” and “What happens to the slurry?” The answers reveal the operation.
Slurry: the wet method's other half
- Contain at the cut: dams, dikes, plastic, and sand tubes keep water where the work is — critical indoors and on above-grade slabs (water finds the ceiling below).
- Vacuum as you go: wet vacuums and slurry vacs pick up the mix of water and concrete fines continuously; floors are left washed-clean, not grey-filmed.
- Never to the storm drain. Slurry is alkaline (high pH) and solids-laden. It is not discharged to storm drains, septic systems, or waterways; it is collected and disposed of through an approved route, and dried residue is handled as solid waste.
- Winter: slurry freezes. Winter interior work needs heated water planning, immediate pickup, and walkway ice control — one more reason January jobs are scheduled, not improvised.
Interior and occupied buildings
Occupied offices, labs, retail, and homes add: plastic containment with sealed seams, negative-air or exhaust where dry-adjacent tasks occur, protection of HVAC intakes (silica in a duct system is a building-wide problem), off-hours scheduling where the owner requires it, and finish protection under every water path. These items are line items with real cost — they appear in the ledger as the interior slurry-control charge, stated rather than buried.
Ask for this page's checklist in any quote conversation. Then request a connection whose first questions include water, power, and containment — because they are the job.