Presented by Simon Reveley at the Hazards Australasia Process Safety Conference 2026, held on 28–30 September at Marvel Stadium in Melbourne, this presentation examines hazardous area classification for hydrogen and argues that the Australasian Supplement can lead to unnecessarily conservative zoning, adding cost and complexity throughout a plant’s life.

Through a worked example involving outdoor hydrogen pipework and valves, Simon compares the Standard and the Supplement approaches and explains how release size, pressure and ventilation inform a hazardous area assessment. Topics include:

• The international Standard and the Australasian Supplement.
• The long-term equipment and operational implications of conservative zoning.
• Why hydrogen needs different consideration from natural gas.
• Release-rate calculations, dilution and ventilation in a Standard-based assessment.