Ethylene Oxide Sterilisation SWMS

Ethylene oxide (EtO) sterilisation is performed in Central Sterile Services Departments (CSSDs), hospital sterilisation units and contract reprocessing facilities to sterilise heat-sensitive medical devices. The work involves cylinder changeover, chamber loading and unloading, aeration/degassing cycles, abator monitoring and routine preventative maintenance on sterilisers and pipework. EtO is classified by IARC as a Group 1 human carcinogen, is a confirmed mutagen and reproductive toxin, and is being reclassified by Safe Work Australia as a Non-Threshold Genotoxic Carcinogen (NTGC) effective 1 December 2026 — meaning no safe airborne concentration can be established and exposure must be reduced As Low As Reasonably Practicable (ALARP). A Safe Work Method Statement is mandatory under WHS Regulations r.299 because the task involves use of a hazardous chemical with acute and chronic health effects, and may also constitute high-risk construction or confined space work. The SWMS documents hazard identification, hierarchy-based controls, atmospheric monitoring, emergency response and health surveillance obligations under Schedule 14.

Hazards identified

7 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Elimination — Substitute EtO-sterilisable devices with steam, hydrogen peroxide plasma or gamma-irradiated single-use equivalents where device manufacturer instructions permit, eliminating EtO exposure entirely.
2. 2Elimination — Decommission legacy gravity-displacement sterilisers and replace with sealed single-dose cartridge systems (e.g. 100% EtO micro-dose units) to remove bulk cylinder handling risk.
3. 3Substitution — Where elimination not viable, substitute 100% EtO cylinders with diluted EtO/CO2 mixtures only where validated under AS/NZS ISO 11135:2019 cycle parameters, reducing flammability envelope.
4. 4Engineering — Install dedicated EtO room with 10+ air changes/hour negative-pressure ventilation, continuous photoionisation detector (PID) monitoring with audible alarm at 1 ppm, and interlocked door systems per AS 1668.2.
5. 5Engineering — Fit catalytic abator achieving 99.9% destruction efficiency on chamber exhaust and aeration vents, with differential pressure monitoring and automated cycle interlock on abator failure.
6. 6Engineering — Provide cylinder hand-truck with chain restraint, leak-detection at every Compressed Gas Association (CGA) fitting connection, and remote pneumatic cylinder valve actuation eliminating manual handling at the valve.
7. 7Administrative — Issue Confined Space Entry Permit per AS 2865:2009 before any chamber entry; require atmospheric testing for EtO <1 ppm, O2 19.5–23.5%, and standby rescue attendant with retrieval system.
8. 8Administrative — Mandate biological and exposure health surveillance per WHS Reg Schedule 14 including baseline and annual haematology, with records retained 30 years; consult HSRs on ALARP reviews quarterly.
9. 9PPE — Supply Sundström SR200 full-facepiece with A2B2E2K2-P3 cartridges or supplied-air respirator for cylinder changeover; butyl rubber gloves (≥0.4 mm), chemical splash apron, and safety boots compliant with AS/NZS 1716.
10. 10PPE — Provide emergency escape respirators (10-minute SCBA) mounted at each exit and personal EtO badge dosimeters worn for full shift, analysed weekly to verify ALARP and inform control review.

Applicable Codes of Practice

Worked example

At a metropolitan tertiary hospital CSSD, a senior steriliser technician is scheduled to perform a Friday-morning EtO cylinder changeover and run a load of cardiac catheters through a 100% EtO cycle. At the 0700 pre-start brief, the team opens this SWMS on the department tablet. The technician walks the assistant through the hazard register, highlighting the acute inhalation and flammability hazards from the cylinder swap. They confirm the engineering controls listed in the SWMS are functional: PID monitor displays 0.0 ppm background, room ventilation differential pressure gauge reads negative, and the catalytic abator is online. The SWMS calls for supplied-air respirators during cylinder breaking — both workers don Sundström SR200 units with airline supply and butyl gauntlets, and a third worker is assigned as door-watch with the emergency SCBA accessible. Both workers sign the SWMS sign-on register on the tablet. Midway through the changeover, the PID alarms at 1.2 ppm; following the SWMS escalation procedure, the team immediately closes the cylinder valve, evacuates the room, and waits for ventilation to clear the atmosphere below 0.5 ppm before re-entry. The supervisor records the deviation, adds 'recheck CGA fitting torque to 35 Nm' as a SWMS amendment, and re-briefs both workers before resuming. The load runs successfully and the amended SWMS is filed against the cycle record.

Related legislation

• WHS Act 2011 (model)
• WHS Regulation 2025
• AS 2865 — Confined spaces

Frequently asked questions