From 1 December 2026, once WEL are implemented, respirable barium sulfate carries an 8-hour TWA of 1.35 mg/m³. Inhalable barium sulfate is separate. Until 30 November 2026, apply WES and confirm commencement with the WHS regulator.
Fraction and SEGs
Respirable sampling answers 1.35 mg/m³; inhalable sampling answers another listing. Define SEGs by powder intensity, record open transfer versus resuspended dust, plan paired strategies if needed, and document the sampler head. Typical settings are mud plants, weigh-out, milling, pack-out and maintenance. Do not miss cleaners, forklift drivers or labs.
Monitoring plan
For a barite hopper, separate tip operators, clean-down crew and filter contractors. Use personal full-shift samples across at least two campaign days plus task samples for filter work. Log hood, bag type, drop height and cleaning method.
- Use a respirable size-selective head; document flow and calibration.
- Use gravimetric analysis, blanks and limits suited to 1.35 mg/m³.
- Include dusty bursts and enough shifts to show variability.
- Report LOD/LOQ, duration and partial-shift assumptions.
Interpretation
Use 1.35 mg/m³ as a planning benchmark now; from 1 Dec compare respirable 8-hour TWAs, not inhalable results. Do not use total-dust data, invent a STEL or claim early adoption without a regulator reference. Near-WEL results trigger redesign. Contact Occ Hygiene.
