Tunnelling puts people and diesel plant in the same confined air volume for long shifts. Diesel particulate matter (DPM) is the particulate fraction of diesel exhaust that occupational hygienists sample when discussing elemental carbon in a heading, portal or plant bay.
From 1 December 2026, Safe Work Australia’s national list introduces a Workplace Exposure Limit for DPM where none existed before on the SWA WES list. Until 30 November 2026, continue to manage risk under the current WES regime and jurisdictional WHS laws. From 1 December, apply the WEL once given effect by your regulator.
What the WEL actually says
The substance is diesel particulate matter measured as respirable elemental carbon, with an 8-hour TWA of 0.01 mg/m³. Do not substitute CO, opacity or nuisance dust measurements for EC speciation.
Build tunnelling-specific SEGs
- Face production plant and non-cabin workers
- Staging, traffic control and congestion zones
- Maintenance, cold starts and DPF service
- Filtered cabin operators and portal or surface plant
Map task, plant and ventilation state rather than relying on the organisational chart. Include contractors and labour-hire workers in the same exposure logic.
Monitoring readiness
Use full-shift personal respirable EC samples on high-likelihood SEGs, supplemented with task samples during start-up, staging peaks and fan outages. Agree the analyte, fraction, collection media, laboratory method, reporting limits and chain of custody before sampling. Log plant mix, idle time, fan status, DPF faults and cabin filter condition.
Controls and December checklist
Use the hierarchy of controls: plant selection and DPF integrity, ventilation verification, traffic management and maintenance controls before relying on RPE. Re-baseline SEGs and LOQ expectations against 0.01 mg/m³, then verify engineering changes using comparable SEGs and plant intensity.
Reports should state the analyte, number of personal TWAs, range against 0.01 mg/m³, dominant tasks and plant states, and whether controls require work before 1 December 2026. Confirm jurisdictional implementation with the WHS regulator.
Key takeaway
DPM readiness is a practical monitoring and controls project: define the EC method, sample the people most likely to be exposed, and make the December transition language explicit.
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