**Respirable crystalline silica (RCS)** remains on Australia’s Workplace Exposure Limits list at **0.05 mg/m³** (respirable). On **1 December 2026**, RCS is in the **held / nine carve-out** set — it does **not** tighten to **0.025 mg/m³** that day. Until **30 November 2026**, apply the current WES regime. From **1 December 2026**, apply WEL once implemented — **confirm with the WHS regulator**.
This note stays inside published values: **0.05 mg/m³** respirable. **Never** write that RCS becomes 0.025 on 1 December 2026. “Stays at 0.05” does not retire SFARP; the WEL is a ceiling, not an aim point.
## Start every brief by killing the 0.025 myth
Client packs and toolbox decks still circulate the wrong December sentence. Correct it once, in writing, at the top of the method and executive summary:
– **What moves on 1 Dec 2026:** WES→WEL rename for the list; many other entries change; new listings appear (including DPM as respirable EC).
– **What does not move for RCS that day:** the numeric limit — **0.05 mg/m³** stays; **not** 0.025.
If older international or guidance debates used lower numbers, cite them only as context for why further Australian impact work was requested for the nine — never as the live SWA WEL for December messaging.
## Characterise the aerosol before choosing a method
RCS profiles in tunnelling typically include:
1. **Face cutting / boring / drilling** — silica-bearing ground → respirable quartz (and other crystalline forms where relevant)
2. **Shotcrete / concrete works** — product silica content plus application and rebound dust
3. **Mucking, conveyors, spoil** — resuspension and transfer points
4. **Maintenance on dusty plant and ducts** — brief, intense, often missed
5. **Re-entry / survey** after dusty tasks while air is still loaded
Agree with the laboratory:
– Analyte **respirable crystalline silica** (specify crystalline forms reported — e.g. quartz — as the lab package requires)
– Reporting units **mg/m³**
– Size selection matching the **respirable** convention used for WEL comparison
– XRD / IR (or defended equivalent) method appropriate to the matrix and expected concentration
– LOQ relative to **0.05 mg/m³** so non-detects can support decisions
A gravimetric “total dust” or inhalable-only habit without crystalline silica analysis is a weak basis for claiming RCS compliance against **0.05 mg/m³**.
## SEG walkthrough
Example: mixed ground with silica relevance, shotcrete cycle, spoil handling, some cabin plant.
1. **SEG — cabin production operators** — full-shift personal; note cabin integrity.
2. **SEG — non-cabin face / support** — do not average into cabin results.
3. **SEG — drilling / rockbolt / charge** — task peaks matter for control diagnosis.
4. **SEG — shotcrete / concrete** — product and method dependent; document assumptions.
5. **SEG — spoil / conveyor / transfer** — resuspension SEGs that production mid-shift samples miss.
6. **SEG — maintainers / duct clean** — short task samples; contractors included.
Pre-write decision rules: results trending toward **0.05 mg/m³** → wet methods / ventilation / enclosure before long-term reliance on RPE. Map **task + material + ventilation state**.
## Monitoring strategy
Recommended structure:
– **SEG map** by dust-generating task and cabin status, including contractors
– **Full-shift personal samples** on high-likelihood SEGs; **task samples** during drilling peaks, shotcrete, and spoil transfer
– **Static samples** only as diagnostics (ventilation, transfer points) — not personal TWA substitutes
– **Replicates** across production rates and ground types where silica content varies
– **Field blanks**, chain-of-custody, and matrix notes (shotcrete vs rock) clear enough for contested results
– **Covariates** — wet method on/off, fan status, production rate, cabin filter condition, housekeeping method
### Method cues that prevent rework
– State respirable fraction and crystalline silica method explicitly
– Match LOQ to decisions near **0.05 mg/m³**
– Record RPE use during sampling
– Do not merge RCS tables with DPM EC tables even when SEGs share geography
– Keep health-monitoring referrals tied to the same SEG logic used for air results
## Interpretation against 0.05 mg/m³
– Use **0.05 mg/m³** as the live planning and compliance comparator (once WEL is in force)
– Report 8-hour TWAs with shift duration and any adjustment stated
– Place LOD/LOQ in context; “ND” alone is not a clearance narrative
– Present task peaks as control diagnostics
– Recommend action **below** the ceiling — SFARP does not wait for exceedance
– After engineering changes, verify with the same SEGs and fraction
AIOH’s **December 2018** RCS paper remains useful for why full-shift monitoring and early action matter. Treat it as professional guidance. Do not paste older guidance numbers into reports as if they replaced the SWA WEL without checking the live list.
## Reporting language that survives client and regulator review
Keep the method paragraph and executive summary aligned on four points:
1. **Fraction and analyte** — respirable crystalline silica; method named; LOQ stated relative to **0.05 mg/m³**
2. **December numeric fact** — RCS **stays at 0.05**; it does **not** become **0.025** on 1 December 2026
3. **SFARP below the ceiling** — investigation and control actions are not reserved for exceedances only
4. **SEG coverage** — which tasks were characterised, which remain qualitative, and what would be required to extend the conclusion
When both DPM and RCS sit on the same project, keep separate result tables, separate method paragraphs, and separate decision rules. Shared ventilation helps both hazards; shared spreadsheet columns usually confuse both.
If ground silica content is uncertain, write the assumption and the verification path (geology notes, product SDS for shotcrete/concrete, or exploratory samples) rather than implying a statutory “no silica” conclusion you cannot defend.
For multi-jurisdiction clients, map CoP / silica-plan expectations at a high level in an appendix — without inventing prosecution stories or claiming a national numeric cut that the WEL list does not make on December day one.
## Transition communication to clients
| Period | RCS messaging |
|—|—|
| To 30 Nov 2026 | WES regime; RCS planning number **0.05 mg/m³**; SFARP below the ceiling |
| From 1 Dec 2026 | WEL **0.05 mg/m³** once jurisdictionally in force — **not** 0.025 that day |
Never invent early adoption claims. Never invent a December RCS cut to 0.025.
## Control hierarchy cues tied to monitoring outcomes
Translate numbers near **0.05 mg/m³** into hierarchy-ordered actions:
– **Eliminate / substitute** — method choices that avoid dry disturbance where practicable
– **Engineering** — verified ventilation, cabins, water suppression / LEV on cutting and drilling
– **Administrative** — exclusion/re-entry, CoP-aligned silica plans, training tied to heading tasks
– **PPE** — RPE for residual risk only
– **Health monitoring** — cohort defined by SEGs and air evidence
## Common failure modes
– Toolbox or board text saying RCS → **0.025** on 1 Dec 2026
– Using total/inhalable dust without crystalline silica analysis to “clear” **0.05 mg/m³**
– One underground SEG that hides face, shotcrete, and spoil differences
– Omitting fraction and method from the method section
– Treating a single under-limit day as programme clearance
– Disconnecting health monitoring from the SEGs that generate dust
## FAQ — technical
### Does “held at 0.05” change how we sample?
No — still respirable crystalline silica, still full-shift preference where practicable, still LOQ fit for **0.05 mg/m³**. What changes is report language: do not imply a December numeric cut.
### Can static samples show WEL compliance?
No. Personal 8-h TWAs answer the WEL comparison.
### What belongs in the executive summary?
Analyte and fraction, n of personal TWAs, range vs **0.05 mg/m³**, dominant tasks, explicit statement that RCS stays at 0.05 on 1 Dec 2026 (not 0.025), and whether controls need work (subject to jurisdictional WEL commencement).
### How should we discuss lower international numbers?
As background to the nine-chemical further-work decision — never as Australia’s December WEL for RCS.
## Sources
– SWA Decision RIS outcome / nine carve-outs: RCS unchanged on 1 Dec 2026; stays **0.05 mg/m³**
– AIOH, *Respirable Crystalline Silica* position paper (December 2018) — hygiene framing only
– SWA WEL / WES changes page: https://www.safeworkaustralia.gov.au/safety-topic/managing-health-and-safety/workplace-exposure-limits-airborne-contaminants/changes-between-wes-and-wel
## Technical support
For respirable crystalline silica method selection, SEG design in headings, or interpretation against **0.05 mg/m³** (including December messaging that avoids the 0.025 myth), see [occhygiene.com.au](https://occhygiene.com.au).
