Mechanical Workshop WEL Changes Guide — Welding, Exhaust, and Solvent Limits
Mechanical workshops, fabrication shops, and auto body repair facilities face multiple Workplace Exposure Limit changes on 1 December 2026. Welding fumes reduce from 5 mg/m3 to 1 mg/m3 respirable, an 80% reduction. Nitric oxide, the combustion gas relevant to exhaust fume exposure, tightens from 25 ppm to 2 ppm, a 92% reduction. Isocyanates retain the TWA of 0.02 mg/m3 but gain a new STEL of 0.07 mg/m3 for short-term peak exposures during spray painting.
This guide explains the specific WEL changes relevant to mechanical workshops, identifies the highest-risk tasks and processes, outlines the monitoring and control obligations under WHS Regulation 2025, and provides a practical compliance timeline. The guide covers welding fume management, exhaust gas extraction, solvent exposure control, and isocyanate management for workshops that include spray painting operations.
All values in this guide reflect the corrected WEL figures published by Safe Work Australia. Nitrogen dioxide (NO2) is a deferred substance and remains at 3 ppm pending ministerial impact analysis. Xylene remains unchanged at 80 ppm. The isocyanate TWA of 0.02 mg/m3 is not changing; only the new STEL of 0.07 mg/m3 is added.
What You Get
- ✓Complete list of WEL changes affecting mechanical and fabrication workshops
- ✓Welding fume exposure profiles by process type (MIG, TIG, FCAW, SMAW)
- ✓Nitric oxide vs nitrogen dioxide clarification and monitoring requirements
- ✓Isocyanate STEL monitoring for workshops with spray painting
- ✓Local exhaust ventilation design guidance for welding and grinding
- ✓RPE selection and fit testing requirements for workshop operations
- ✓Step-by-step compliance timeline from now to December 2026
- ✓Enforcement penalty summary for WHS Regulation 2025 offences
Inside the Guide
Welding Fumes — 80% Reduction
The welding fume WEL drops from 5 to 1 mg/m3 respirable. This guide explains what this means for different welding processes, how to assess your current exposure levels, and the engineering controls needed to achieve the new limit. Most workshops without local exhaust ventilation will exceed the new standard.
Nitric Oxide — The Combustion Gas That Changed
Nitric oxide (NO) reduces from 25 to 2 ppm, a 92% reduction. This affects workshops with engine testing, exhaust extraction, and diesel equipment. Nitrogen dioxide (NO2) is deferred at 3 ppm and is not changing. The guide clarifies which gas is which and what monitoring is required.
Isocyanates — New STEL
The isocyanate TWA stays at 0.02 mg/m3, already one of the lowest limits on the WEL list. A new STEL of 0.07 mg/m3 caps short-term peak exposures during active spraying. The guide covers monitoring methods, spray booth requirements, and RPE selection for isocyanate work.
Ventilation and Control Design
The guide provides design guidance for local exhaust ventilation systems in workshops, including fume extraction arm placement, capture velocity requirements, ductwork sizing, and fan selection. Each recommendation is linked to the specific WEL reduction it addresses.
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