Structural Fumigation (Methyl Bromide / Sulfuryl) SWMS

Structural fumigation using methyl bromide or sulfuryl fluoride is one of the highest-consequence activities in the Australian pest management industry. The work involves sealing an entire structure (or shipping container, silo, mill or heritage building) under gas-tight tarpaulins, releasing acutely toxic fumigant at lethal concentrations, monitoring containment over 24-72 hours, then aerating and clearance-testing before re-entry. Because the fumigants used are Schedule 7 dangerous poisons capable of causing fatal pulmonary oedema, central nervous system damage and cardiac arrhythmia at low ppm exposures, every fumigation episode constitutes High Risk Construction Work under WHS Regulation r291 and triggers mandatory SWMS preparation, worker consultation and PCBU sign-off before any cylinder is cracked. This SWMS template documents the hazard controls, exclusion zones, gas-detection regime and emergency arrangements required to discharge the PCBU's primary duty of care under s19 of the WHS Act and to satisfy fumigant licensing conditions issued by state agriculture and health regulators.

Hazards identified

7 hazards covered, sorted by priority.

Control measures

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

1. 1Elimination — Substitute fumigation entirely with heat treatment (56°C core for 30 min) or controlled-atmosphere nitrogen where target pest susceptibility allows, removing the toxic gas hazard.
2. 2Elimination — Verify the structure is fully evacuated of all persons, pets and livestock within a 10 m perimeter and lock-off all access points before any gas release begins.
3. 3Substitution — Where fumigation is unavoidable, select sulfuryl fluoride over methyl bromide for non-quarantine work given lower acute toxicity profile and Montreal Protocol obligations.
4. 4Substitution — Use pre-mixed low-concentration formulations and dose calculators rather than volumetric estimation to reduce overdose and residual gas pocket risk.
5. 5Engineering — Deploy continuous Interscan GasTech or Spectros MIRAN SapphIRe analyser with audible 1 ppm alarm at perimeter, calibrated within 24 hours per AS/NZS 60079 sensor protocols.
6. 6Engineering — Install gas-tight polyethylene tarpaulin with sand-snake ground seal, pressure-test envelope to detect leaks before cylinder discharge per AFAS fumigation standard.
7. 7Administrative — Implement written fumigation management plan, 24/7 site warden roster, neighbour notification 48 hours prior, and exclusion zone placarding under AS 1319 sign requirements.
8. 8Administrative — Conduct pre-start SWMS briefing, verify current fumigant licence and SCBA medical fitness certificate for every operator before work commences.
9. 9PPE — Mandate full-face SCBA (positive pressure, 30-minute minimum cylinder) for any entry above 1 ppm; air-purifying respirators are prohibited for methyl bromide work.
10. 10PPE — Wear chemical-resistant Viton gloves, anti-static coveralls and continuous personal dosimeter badge during cylinder handling, monitoring rounds and aeration sampling.

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

On a Monday afternoon a fumigation crew mobilises to a regional flour mill scheduled for sulfuryl fluoride treatment against khapra beetle. The lead fumigator opens this SWMS on a tablet at the pre-start brief held at the mill's amenities block, 25 metres outside the exclusion zone. He walks the two-person crew and the mill's site warden through each of the seven listed hazards, pausing at the 'unauthorised entry' line item because the mill abuts a public rail corridor — the team agrees to add a third placarded barricade and brief the rail operator's controller before gas release. Each crew member signs the SWMS sign-on register, confirms current SCBA medical clearance, and witnesses calibration of the Interscan analyser against a 5 ppm span gas. During the 36-hour exposure phase, the warden conducts hourly perimeter monitoring rounds; at the 14-hour mark the analyser alarms at 2 ppm near a southern tarpaulin seam. The team consults the SWMS engineering control referencing tarpaulin re-sealing, dons SCBA per the PPE control, and re-applies a sand-snake seal. The corrective action and detector reading are logged on the SWMS amendment sheet, re-signed by the crew, and filed with the clearance certificate before workers are permitted to re-enter the mill.

Related legislation

• WHS Act 2011 (model)
• WHS Regulation 2025
• Managing Risks of Hazardous Chemicals CoP; APVMA registered product label requirements