Does Fluorine-Free Foam Work at Sea?

Not as reliably as the foam it replaces — and the shortfall shows up exactly where ships fight fires. With PFOS banned from vessels from January 2026 and the wider EU PFAS phase-out running to 2030, operators are switching to fluorine-free (F3) foam. But F3 loses performance with seawater, non-aspirated nozzles and cold, windy decks — the marine case — and no foam of any chemistry stops a lithium-ion battery fire. The swap is mandatory; treating it as a like-for-like drop-in is the mistake.

Two bans, not one

The maritime PFOS ban is only the leading edge of a wider phase-out. SOLAS Regulation II-2/10.11, adopted under resolution MSC.532(107), prohibits fire-extinguishing media containing PFOS above 10 mg/kg from 1 January 2026, fixed systems and portables alike. Running in parallel, the EU's Commission Regulation (EU) 2025/1988 restricts the whole PFAS family in firefighting foams: no marketing of PFAS-containing foams after 23 October 2026 (with a portable alcohol-resistant-extinguisher extension to 23 April 2027), mandatory warning labels from the same date, and a full ban on use at or above 1 mg/L from 23 October 2030. An operator is not swapping one compound out — the entire fluorinated-foam category is going away, and stock bought now has to anticipate it.

Why fluorine-free foam is harder at sea

Because F3 foams lose the film that made AFFF forgiving. Legacy aqueous film-forming foam laid down a thin aqueous film that sealed hydrocarbon vapour ahead of the foam blanket; fluorine-free foams do not form that film and rely on the blanket alone, which makes them far more sensitive to how they are applied. The reported marine drawbacks line up with shipboard reality: reduced performance with seawater, higher viscosity at low temperature, and a plume that is harder to direct in wind. Some foam test protocols are run with potable water, which can flatter a foam that then underperforms on seawater — so the certificate matters: EN 1568:2018 parts 3 and 4 include seawater testing, and type-approved F3 foams meeting IMO/SOLAS/MED standards do exist. A compliant swap is achievable, but it is not automatically a like-for-like one.

It still doesn't touch an EV fire

The point that matters most for a car deck: no foam, fluorinated or not, stops lithium-ion thermal runaway. Foam suppresses the flame and vapour of a burning liquid; a cell in runaway is a self-oxidising internal reaction that keeps generating its own heat and reignites after any knockdown. The tools that actually change an EV pack's outcome are massive water cooling and boundary control, plus the time that early detection buys — not the foam concentrate in the locker. The foam transition is a hydrocarbon- and machinery-fire question. The battery fire on the same deck stays a detection-and-cooling one, unchanged by which foam is aboard.

What an operator should actually do

Treat the swap as a fire-capability decision, not a purchasing formality. Three checks close most of the gap.

• Buy on seawater performance: require EN 1568:2018 parts 3 and 4 certification (which tests seawater) and an IMO/MED type approval — not a potable-water test result.
• Re-check application rates and equipment: F3 may need higher rates or aspirated delivery to match the old performance, so the fixed system's original design assumptions may not carry over.
• Plan for both timelines: the SOLAS PFOS date and the EU PFAS phase-out (2026 / 2027 / 2030) — and keep the EV-fire plan separate, because foam is for the liquid and machinery fire load, not the battery deck.

What it means for owners and underwriters

For operators, the foam swap is not a substitution to sign off blind — chosen badly, it can reduce firefighting performance in the marine conditions that matter, on decks where the fastest-growing fire risk is battery cargo that foam cannot stop anyway. For underwriters, a fleet mid-transition may be carrying F3 foam that behaves differently from the AFFF the vessel's fire plan assumed. The change is mandatory and right environmentally, but it is a moment to re-examine both the hydrocarbon-fire capability and the EV-fire gap — not to assume the swap leaves either untouched.

Sources

• 1. Commission Regulation (EU) 2025/1988 — restriction of PFAS in firefighting foams: marketing of PFAS-containing foams banned after 23 October 2026 (portable alcohol-resistant extinguishers to 23 April 2027), warning labels from 23 October 2026, and use banned at ≥1 mg/L from 23 October 2030 — eur-lex.europa.eu.
• 2. IMO — SOLAS Reg. II-2/10.11, resolution MSC.532(107): PFOS in fire-extinguishing media prohibited above 10 mg/kg from 1 January 2026 (fixed and portable); see DNV and Lloyd's Register class news for the ship-application summary — imo.org / dnv.com / lr.org.
• 3. EN 1568:2018 parts 3 & 4 (foam performance, including seawater testing) and LASTFIRE (JOIFF, 2018–2022) large-scale foam-performance research on the fluorine-free transition — the basis for the F3 marine-performance caveats. [VERIFY: the specific seawater / low-temperature-viscosity / wind underperformance points are drawn from EU F3-transition and foam-industry guidance, not a marine-authority primary — confirm before publish.]
• 4. IUMI / US Coast Guard — lithium-ion battery fires are not extinguished by foam; suppression cools and controls but does not stop the internal thermal-runaway reaction, which reignites — iumi.com.
• 5. Companion RoRoSAFE analysis — 'What the 2026 PFOS Foam Ban Means for RoRo' and 'Delphine Fire: What CO₂ Couldn't Prevent'.