Diacetyl is a new airborne contaminant with an 8-hour TWA of 0.04 mg/m³ (0.01 ppm) and a STEL of 0.07 mg/m³ (0.02 ppm). WES remains the reference until 30 November 2026; from 1 December 2026 WEL applies once implemented—verify with the WHS regulator.
What to measure
Diacetyl is usually vapour, with aerosol possible during powder tip, spray or mist-generating clean-down. Carry both TWA and STEL values into the plan; do not bury short-term results as task notes.
SEGs and sampling
- Flavour weigh/tip, mixer/kettle dose and heated processing.
- Clean-down, maintenance, laboratory, sensory and QC crews.
Collect full-shift personal samples for TWA and short-term samples suitable for STEL comparison. Agree sorbent/media, recovery, capacity, breakthrough, blanks, storage and reporting limits with the laboratory relative to 0.01 and 0.02 ppm. Record open minutes, lid/LEV status, temperature and RPE. State the STEL averaging basis and LOD/LOQ.
Interpretation and controls
Compare TWA to 0.04 mg/m³ (0.01 ppm) and short-term results to 0.07 mg/m³ (0.02 ppm). A passing TWA does not establish STEL comfort. Use diacetyl-free or closed formulations, enclosed tip/dose, LEV at open points, lid discipline and purge-before-break; then compatible gloves and fit-tested vapour RPE.
