Sulfuryl fluoride (SF) is a fumigant gas approved as a fourth treatment for wood packaging under ISPM 15, alongside heat treatment, methyl bromide and dielectric heating. Wood treated with SF is marked with the code SF. The approved schedule applies only to debarked wood up to 20 cm thick, at a minimum of 20 °C, and takes 24 to 48 hours.
Where SF fits among ISPM 15 treatments
ISPM 15 originally recognized two treatments: heat treatment (HT) and methyl bromide fumigation (MB). Dielectric heating (DH) was added in 2013. Sulfuryl fluoride followed after years of development and consultation: it was adopted in 2017 as an international phytosanitary treatment for nematodes and insects in debarked wood, and incorporated into the revised ISPM 15 published in 2018. The overall history is in ISPM 15 explained.
The main motivation was to provide a fumigant alternative to methyl bromide, which is controlled under the Montreal Protocol because it depletes the ozone layer; see methyl bromide. A second approved fumigant gives treatment providers and importers more options than a single chemical.
The approved schedule
The IPPC treatment is titled Sulphuryl fluoride fumigation treatment for nematodes and insects in debarked wood. The test organisms behind it include the pine wood nematode (Bursaphelenchus xylophilus) and the insects Anoplophora glabripennis (Asian longhorned beetle), Anobium punctatum (common furniture beetle) and Arhopalus tristis. The treatment is defined by concentration × time product (CT), the integral of gas concentration over the exposure period, and by a minimum final concentration:
| Minimum temperature | Exposure | Minimum CT | Minimum final concentration |
|---|---|---|---|
| 30 °C or above | 24 hours | 1,400 g·h/m³ | 41 g/m³ |
| 20 °C or above | 48 hours | 3,000 g·h/m³ | 29 g/m³ |
Other conditions in the schedule:
- Maximum thickness: no piece of wood may exceed 20 cm in its smallest cross-section dimension.
- Moisture content: not above 75% on a dry-weight basis.
- Debarked wood only. Bark can shield pests and absorb gas; see the debarking requirement.
- Minimum temperature: 20 °C throughout the wood and the load. Cold weather therefore limits when SF can be used, and a fumigation chamber or tarpaulin may need heating.
- Gas readings: concentration is measured at several points during exposure, at a minimum at 2, 4 and 24 hours (with an additional reading at 48 hours for the 20 °C schedule).
The standard also gives example dosing: a starting dose of about 82 g/m³ for the 30 °C schedule and about 120 g/m³ for the 20 °C schedule, with more readings through the exposure. Real doses depend on the load, enclosure tightness and temperature, and must be adjusted by a licensed fumigator so that the CT and final concentration are actually met.
How SF differs from HT and MB
| SF | MB | HT | |
|---|---|---|---|
| Method | Gas | Gas | Heat |
| Exposure | 24–48 h | 24 h | 30 min at core (plus heating time) |
| Minimum temperature | 20 °C | 10 °C | 56 °C wood core |
| Residues | Aerated before release | Aerated before release | None |
| Mark code | SF | MB | HT |
Methyl bromide's 24-hour schedule starts at a lower minimum temperature (10 °C) than SF, so it is more flexible in cold conditions; SF is slower and needs warmth. Both fumigants require gas-tight enclosures, trained operators and clearance times. For comparison, the heat method is described in heat treatment.
Safety and environment
SF is a toxic gas, and fumigation is a regulated activity. In most countries only licensed fumigators may carry it out, using gas monitors, warning signs and aeration procedures before the load is released. Operators must also manage emissions: sulfuryl fluoride does not deplete the ozone layer, but it is a potent greenhouse gas, so some jurisdictions restrict venting or require capture. Check local fumigation and environmental rules before choosing SF.
Acceptance and limits in practice
- Authorization: the producer or fumigation provider must be authorized by the national plant protection organization (NPPO) to apply SF and mark with the SF code. See ISPM 15 certification.
- Acceptance by importers: each NPPO decides when to apply a revised standard in its import rules. Before shipping SF-marked packaging, confirm that the destination accepts it. Lists of accepting countries could not be verified and are not given here; see ISPM 15 country rules.
- Scope of effectiveness: the schedule is validated for the nematodes and insects used in its testing. Fungi and other organisms are not claimed to be covered, and mold control remains a moisture-management issue; see mould and blue stain.
- Records: gas readings, temperatures, dose, enclosure volume and times must be recorded, and the stamp applied only after the treatment is complete; see ISPM 15 documentation.
- The mark: the SF code appears with the symbol, country code and producer number, as described in the ISPM 15 mark.
For most pallet producers heat treatment remains cheaper and simpler, and SF is used mainly where fumigation is already established practice, or where heating is impractical.
Frequently asked questions
When was sulfuryl fluoride added to ISPM 15?
The treatment was adopted in 2017 and included in the revised ISPM 15 published in 2018.
What temperature and time does SF require?
At 30 °C or above, 24 hours with a CT of at least 1,400 g·h/m³ and 41 g/m³ final concentration; at 20 °C or above, 48 hours with a CT of at least 3,000 g·h/m³ and 29 g/m³.
Does SF work on wood with bark?
No. The approved schedule is for debarked wood, with a maximum thickness of 20 cm and moisture content no higher than 75% (dry basis).
Is SF replacing methyl bromide?
It offers an alternative fumigant, but heat treatment is the dominant method worldwide and replaces methyl bromide in most cases.
Sources
- Sulphuryl fluoride fumigation treatment for nematodes and insects in debarked wood (PT 23) — International Plant Protection Convention
- ISPM 15 (2018 edition, Korean translation) — International Plant Protection Convention
- Draft Annexes 1 and 2 to ISPM 15: sulphuryl fluoride — International Plant Protection Convention
- ISPM 15: inception to current implementation — Standards and Trade Development Facility
- ISPM 15 — Wikipedia