Container fumigation is the treatment of a closed container, and the cargo inside it, with a toxic gas that kills insects and other pests before the goods cross a border. Destination plant health authorities demand it for certain goods and origins, and the fumigation provider documents it on a fumigation certificate. The key takeaway for shippers is that there are two separate questions: did the treatment satisfy the importing country (the certificate), and is the box still full of gas (the IMDG Code rules for UN 3359 fumigated units and the gas check before unloading). A valid certificate answers the first question only.
Fumigation sits beside two neighbouring requirements that shippers often blur together: the ISPM 15 rules for wood packaging and the phytosanitary certificate and import permit that plant and plant-product shipments may need. This guide covers what is specific to fumigating the container itself.
Why containers are fumigated
Almost all container fumigation is done for one of three reasons:
- Quarantine requirements at destination. The importing country names a pest it does not want and requires treatment of goods from places where that pest lives. Stored-product pests in grain, timber borers and hitchhiking insects are typical targets.
- Pre-shipment requirements. Some exporting or importing countries require a treatment shortly before export as an official condition of trade. Under the Montreal Protocol framework, a pre-shipment application is one applied within 21 days before export to meet an official requirement of the importing or exporting country.
- Commercial protection of the cargo. Exporters of foodstuffs, grain, leather goods, handicrafts, textiles and cane or timber furniture sometimes fumigate to stop infestation spoiling the goods on a long voyage, even where no authority asks for it. Britannia P&I lists exactly these cargo types as the ones most likely to travel fumigated.
Seasonal measures: the brown marmorated stink bug
The best-known seasonal requirement is the brown marmorated stink bug (BMSB) programme run by Australia and New Zealand. The insect shelters in containers, machinery and vehicles during the northern hemisphere autumn and winter, so both countries apply measures to goods shipped during a defined risk season.
For Australia, the 2026-27 season covers target goods shipped from target risk countries between 1 September 2026 and 30 April 2027 inclusive, and the shipped-on-board date is what counts, not the arrival date. The target risk country list includes the United States and many European countries; as of the Department of Agriculture, Fisheries and Forestry (DAFF) update of August 2026, goods from the United Kingdom, China, Japan and the Republic of Korea face random inspection rather than mandatory treatment. Target high risk goods (broadly wood, iron and steel articles, machinery, vehicles and vessels, by tariff chapter) must be treated. The approved options are heat, methyl bromide, sulfuryl fluoride and, new for 2026-27 as an onshore option, ethyl formate. Break bulk, open-top and flat-rack cargo must be treated offshore before arrival; sealed containers with six hard sides can be treated offshore or onshore. DAFF also removed its Rolled Goods Policy and Safeguarding Arrangements Scheme for this season.
New Zealand applies its own BMSB measures through MPI, mainly to vehicles, machinery and parts. A BMSB treatment only counts for New Zealand if an MPI-approved offshore treatment provider performs it before arrival, and MPI states that goods bound for New Zealand cannot be treated for BMSB in Australia. Confirm the current country list and season dates on the DAFF and MPI pages before booking, because both are revised every year.
The common fumigants, and why methyl bromide is still around
| Fumigant | Typical container use | Points to know |
|---|---|---|
| Methyl bromide | Quarantine treatments of timber, machinery, some foodstuffs; one ISPM 15 treatment code (MB) | Ozone-depleting substance; quarantine and pre-shipment use is exempt from the Montreal Protocol phase-out, but the EU stopped allowing even that use on 18 March 2010 |
| Sulfuryl fluoride | Timber, machinery and BMSB treatments | Not ozone-depleting; increasingly accepted as a methyl bromide alternative where the importing country lists it |
| Phosphine (from aluminium or magnesium phosphide) | Grain, pulses, nuts, dried foods; often applied as tablets or sachets and left to work during the voyage | The fumigant most associated with in-transit fumigation; residue sachets may remain in the box |
| Ethyl formate | Approved by Australia for BMSB, offshore and, from 2026-27, onshore | Acceptance outside Australia varies; check before relying on it |
A common misconception is that methyl bromide is banned. It is more precise to say it was phased out for controlled uses: under the Montreal Protocol, developed countries phased it out by 1 January 2005 and developing (Article 5) countries by 1 January 2015. Article 2H(6) of the Protocol excludes quantities used for quarantine and pre-shipment (QPS) applications from those limits, so methyl bromide remains legal for QPS treatments in many countries, subject to reporting. UNEP's Ozone Secretariat reports that QPS now accounts for the large majority of remaining methyl bromide consumption. The European Union went further: the deadline in Article 12(1) of Regulation (EC) 1005/2009 ended QPS use inside the EU from 18 March 2010, and that regime has since been replaced by Regulation (EU) 2024/590. So an EU exporter cannot simply order a methyl bromide fumigation at origin, even when a destination would accept one.
The fumigation certificate: who issues it and what it proves
The fumigation certificate (sometimes called a treatment certificate or certificate of fumigation) is issued by the treatment provider that carried out the fumigation, not by the carrier and not, usually, by customs. It records what was treated (container numbers, goods, marks), the fumigant, the dose, the exposure period, the temperature, the date and place of treatment and, often, the end-point concentration readings, signed by the fumigator in charge.
The importing country decides whose certificates it accepts. Australia is the clearest example. DAFF runs the Australian Fumigation Accreditation Scheme (AFAS) with participating overseas governments for offshore methyl bromide treatments, and its import conditions require a methyl bromide certificate to carry the provider's AFAS or department-issued identification number. Its methyl bromide conditions have also required the treatment to be completed within 21 days of export. When DAFF suspends a provider, it treats all certificates from that provider as unacceptable from the suspension date, regardless of when the treatment was done, so a shipment can fail on paperwork that looked fine when it left. Other countries rely on the treatment being recorded in the treatment section of an official phytosanitary certificate issued by the exporting country's plant protection organisation.
Three things a fumigation certificate does not do:
- It does not certify the wood packaging under ISPM 15. Each pallet, crate and piece of dunnage still needs the IPPC mark from an authorised provider, as the ISPM 15 guide explains. A fumigated container full of unmarked pallets can still be rejected.
- It does not say the container is free of gas now. It records a treatment at a moment in time.
- It does not stop the destination inspecting. Live pests found on arrival can still trigger re-treatment, re-export or destruction at the importer's cost.
IMDG Code rules for fumigated cargo transport units (UN 3359)
A container that is still under fumigation when it is shipped is regulated as dangerous goods: UN 3359, FUMIGATED CARGO TRANSPORT UNIT, class 9. The rules sit in section 5.5.2 of the IMDG Code (Amendment 42-24, mandatory since 1 January 2026). The main provisions, paraphrased:
- Scope (5.5.2.1). A fumigated unit containing no other dangerous goods is subject only to section 5.5.2. If it also carries other dangerous goods, every provision for those goods applies in full. Only units that can be closed so as to minimise gas escape may be used.
- Training (5.5.2.2). People handling fumigated units must be trained in line with their responsibilities.
- The fumigation warning mark (5.5.2.3). The mark goes at every access point, where anyone opening or entering the unit will see it. It is a rectangle at least 400 mm wide and 300 mm high, black on white, with letters at least 25 mm high, stating that the unit is under fumigation, the fumigant name, the date and time applied, a ventilation date, and DO NOT ENTER. Class 9 placards are not used unless other class 9 goods are inside.
- Ventilation and removal. When the unit has been completely ventilated, by opening the doors or mechanically, the ventilation date is added to the mark. The mark is removed only once the unit has been both ventilated and unloaded.
- Documents (5.5.2.4). The transport document must show "UN 3359, FUMIGATED CARGO TRANSPORT UNIT, 9" (or "class 9"), the date and time of fumigation, and the type and amount of fumigant. The document can be in any form as long as the information is legible and durable. Instructions for disposing of residual fumigant, including any fumigation devices, must also be provided. None of this documentation is needed if the unit was completely ventilated before transport and the ventilation date is on the mark.
The IMO's companion guidance, MSC.1/Circ.1361/Rev.1 (Revised Recommendations on the Safe Use of Pesticides in Ships Applicable to the Fumigation of Cargo Transport Units), adds the operational side: a fumigated unit should not be loaded until the gas has had time to spread through the cargo (24 hours is normally considered adequate), fumigant should never be applied once the unit is aboard, and in-transit fumigated units are better stowed on deck and clear of living quarters. Some destination and transit ports also expect the vessel to give advance notice of in-transit fumigated units.
| Situation | Warning mark | Dangerous goods documentation |
|---|---|---|
| Fumigated and completely ventilated before transport | Yes, with the ventilation date filled in | Not required under 5.5.2 |
| Fumigated and not completely ventilated (in-transit fumigation) | Yes, at every access point | Required: UN 3359 entry, date and time, fumigant type and amount, residue disposal instructions |
| Fumigated unit also carrying other dangerous goods | Yes | Full IMDG declaration for the other goods as well |
For a shipper this means one practical decision at booking: will the box be ventilated before it is gated in, or will it travel under gas? If it travels under gas, tell the forwarder and carrier, because it becomes a dangerous goods booking with the dangerous goods declaration and acceptance process that implies. The wider framework is covered in our guide to IMDG and IATA dangerous goods rules.
The safety risk when the doors open
The people most at risk from fumigation are not the fumigators but whoever opens the container at the other end: warehouse staff, inspectors, customs officers and the consignee's own team. Methyl bromide, phosphine and sulfuryl fluoride are dangerous at low concentrations, and EU-OSHA warns that fumigant presence in freight containers "may be undeclared and undocumented, with no external warning signs". Marks get torn off, units are re-stuffed, and some exporters fumigate without telling anyone. Gas can also come from the goods themselves: Britannia P&I notes that some products off-gas formaldehyde or solvents such as toluene and benzene to dangerous levels without any fumigant being involved.
The IMO flowchart and P&I guidance point to the same signs of an unmarked fumigated unit: taped doors or vents, sachets or piles of powdery residue, an unusual odour, and the nature, origin and destination of the cargo. Good practice before unloading is:
- Assess the risk before the doors are opened, from the documents and any marks.
- If fumigation is declared or suspected, have a competent person measure the atmosphere with instruments suited to the fumigant. A detector for one gas will not read another.
- Ventilate the unit, ideally in an open, barricaded area, and re-measure. Venting can take many hours, and gas trapped in cartons or bagged goods can be released again as the load is broken down.
- Unload from the doors back. Do not climb or tunnel into the stow to retrieve individual packages.
- Remove the fumigation mark only once the unit is both ventilated and empty, and dispose of residue sachets according to the instructions supplied.
In many ports a specialist issues a gas-free or clearance certificate after measurement. Whether that is legally required depends on the country and its workplace rules, so treat the steps above as the minimum, not the full answer.
How fumigation differs from ISPM 15 heat treatment
ISPM 15 is about the wood packaging: pallets, crates and dunnage are treated, usually by heat (HT), and marked before they are used. Container fumigation is about the whole loaded unit, done because a destination wants the goods treated or because the cargo itself is at risk. A shipment can need both, either or neither. Heat-treated, marked packaging does not remove a BMSB treatment requirement on machinery, and a fumigated container does not cure unmarked dunnage. For the packaging side, see export packaging and palletisation.
What to do next
- Check the destination's current import conditions for your goods and origin, including any seasonal measures such as BMSB, before you book, not after the box is packed.
- Use a treatment provider that the importing country accepts, and check that provider's status shortly before shipment as well as at booking.
- Decide whether the unit will be ventilated before gate-in. If not, declare it as UN 3359 to your forwarder and carrier.
- Warn your consignee in writing that the unit was fumigated, with the fumigant and date, so the receiving warehouse can test before opening.
Fumigation adds time at origin, and a failed treatment adds time and storage at destination, which is where detention and per diem start to bite. If you need a forwarder that regularly handles treated cargo on your lane, more than 29,300 logistics companies are searchable by country and service in the CargoLinked directory, and the public requests board lists freight that shippers have posted for forwarders to quote on directly.
This guide is general information, not legal, customs or biosecurity advice. Fumigation requirements, approved treatments and provider lists change, often every season. Confirm the current rules with the importing country's plant health or biosecurity authority, the current IMDG Code text and a licensed treatment provider before shipping.
