Start hereRules checked 20 October 2026
Foam concentrate is the one fire-fighting medium on board that quietly goes off. It sits in a tank for years, in a hot pump-room or on deck in the sun, and slowly separates, forms sludge or changes its chemistry. Nothing on the outside of the tank tells you. The only way to know whether the foam in your deck foam system would still make a blanket on burning crude oil is to take a sample and test it.
That is why IMO asks for a periodical laboratory analysis of foam concentrate, first within three years of supply and then every year. Since 1 January 2026 there is a second reason to know exactly what is in the tank: SOLAS now bans foam containing PFOS, a persistent and toxic chemical once common in film-forming foams.
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In this lesson
- Foam system records and walk-round on a product tanker
- In plain words
- In detail
- What the rules say
- Flag and class notes
- Key numbers
- What inspectors find
- Quiz: 6 questions
Try it
Foam system records and walk-round on a product tanker
In plain words
Foam is made in three steps. A small amount of foam concentrate (often 1%, 3% or 6%) is mixed into a stream of water by a proportioner. The mixture, called foam solution, is then blown full of air at a nozzle, monitor or generator. The bubbles float on burning oil, shut out the oxygen and stop the fuel vapour rising. Some foams also lay a thin water film on the fuel.
How much air goes in decides the type of foam. Low-expansion foam (a few times its volume of solution) is heavy and wet, and it is thrown by monitors and hand applicators onto a tank deck or an oil spill. High-expansion foam (hundreds of times its volume) is light and dry, and it fills a whole engine room or car deck from the floor up, like bath foam filling a bath.
The concentrate is a chemical product, and it ages. Heat, contamination, air in a half-empty tank, or mixing two products can ruin it. A ruined concentrate still looks like liquid in a tank but makes weak foam that collapses on the fire. The annual lab test checks it, and the crew’s job is to take a good sample, keep the tank full and clean, and never mix products.
In detail
Where foam systems are fitted
| System | Where | Main rule |
|---|---|---|
| Fixed deck foam (low expansion) | Cargo tank deck of oil and chemical tankers | SOLAS II-2/10.8, FSS Code chapter 14 |
| Fixed high-expansion foam | Machinery spaces, cargo pump-rooms, cargo, vehicle, ro-ro and special category spaces (as an alternative to gas or water) | SOLAS II-2/10.4.1, FSS Code chapter 6 section 3 |
| Fixed low-expansion foam | Machinery spaces, where fitted in addition to the required fixed system | SOLAS II-2/10.4.1.2, FSS Code chapter 6 section 4 |
| Portable foam applicators | Machinery spaces, and as fire-fighter equipment | SOLAS II-2/10.5, FSS Code chapter 4 |
| Helideck foam | Helicopter facilities | FSS Code chapter 17 |
Deck foam on tankers. The foam solution supply rate must be the greatest of 0.6 l/min per m² of cargo tanks deck area, 6 l/min per m² of the largest single tank’s horizontal area, or 3 l/min per m² of the area protected by the largest monitor (and at least 1,250 l/min per monitor). There must be concentrate for at least 20 minutes of foam generation on a tanker with inert gas, or 30 minutes without. Each monitor delivers at least 50% of the required rate; each applicator at least 400 l/min with a throw of at least 15 m. Type B concentrate (regular, not alcohol-resistant) protects crude oil, products and non-polar solvents; Type A (alcohol-resistant) is for polar solvents in the IBC Code. Only one type may be supplied.
High-expansion foam in machinery spaces. The system must produce foam at the required rate within 1 minute of release, fill the largest protected space within 10 minutes, and carry enough concentrate for five times the volume of the largest protected space or 30 minutes of full operation, whichever is greater. People re-entering after a discharge must wear breathing apparatus. Alarms in the space must sound for at least 20 seconds before release.
Foam types you will meet on reports
MSC.1/Circ.1312 defines the concentrate families: protein (P), fluoroprotein (FP), film-forming fluoroprotein (FFFP), aqueous film-forming foam (AFF, often called AFFF), synthetic (S), and alcohol-resistant (AR) versions. High-expansion concentrates are approved under MSC/Circ.670, medium-expansion under MSC/Circ.798, and low-expansion under MSC.1/Circ.1312.
The periodical control: what the lab tests
MSC.1/Circ.1312, section 4, lists the periodical tests on concentrate stored on board:
| Test | What it shows | Type approval reference |
|---|---|---|
| Sedimentation | Sludge or particles; sediment must disperse through a 180 µm sieve and not exceed 0.25% by volume | 3.3 |
| pH | Chemical change; type approval range 6 to 9.5 at 20°C | 3.5 |
| Expansion ratio | Whether it still makes enough foam, with simulated seawater | 3.7 |
| 25% drainage time | Whether the foam holds its water (foam stability) | 3.8 |
| Volumic mass (density) | Dilution or concentration changes | 3.11 |
| Small-scale fire test | Protein-based alcohol-resistant concentrates only | 3.14 |
| Chemical stability test with acetone | Protein-based alcohol-resistant concentrates only | 4.7 |
Sedimentation, expansion and drainage are tested on samples first kept at 60°C for 24 hours, which shows how the concentrate behaves after heat stress. The results are compared with the values from type approval and the maker’s batch declaration; the deviation must be within the range accepted by the Administration. A lab report should list each test, the measured value, the reference or limit, and a clear “fit for further use” or “replace” conclusion.
Two wordings of the first-test rule. MSC.1/Circ.1312, section 5, gives the 3-year first interval to all concentrates (except the acetone test for protein-based alcohol-resistant foam, which is done before delivery and yearly). The note to MSC.1/Circ.1432 paragraph 7.4.9 is worded differently: “Except for non-alcohol resistant foam, the first test need not be conducted until 3 years after being supplied to the ship”, which read literally would require regular (Type B) foam to be tested yearly from the start. Panama reproduces that note in its circular, while the Marshall Islands follows Circ.1312. Check which reading your flag and RO apply; testing yearly from delivery satisfies both.
Taking the sample
- Sample size for a periodical control: 2 litres, in a filled container (no air space).
- Make it representative: use the tank’s sampling valve, drain the dead leg first, and take the sample from the circulating or well-mixed concentrate, not from sludge at the bottom or a skin on top. The FSS Code requires a means for the crew to take control samples safely.
- Label the container with ship, tank, product name and batch, date of supply and date of sampling, and send it with the product data to a laboratory or service supplier accepted by the Administration.
- Record the sample and the result in the maintenance records; Marshall Islands asks ships to keep a record of the age of the foam concentrate and every subsequent control.
The other foam system checks
MSC.1/Circ.1432 sets the system checks: monthly, valves and pressure gauges in the right position and range; quarterly, the quantity of concentrate in the storage tank; annually, flow tests of water and foam pumps (with fresh-water flushing afterwards), relief valves, strainers, cross-connections, blowing through high-expansion piping, and the concentrate samples; every five years, internal inspection of control valves, flushing of high-expansion piping, nozzles checked clear, and a test of all proportioners to confirm the mixing ratio is within +30% to -10% of the nominal ratio. At installation, the FSS Code is stricter: +30% to -0%.
PFOS: the 2026 ban
SOLAS regulation II-2/10.11, added by resolution MSC.532(107), prohibits the use or storage of fire-extinguishing media containing perfluorooctane sulfonic acid (PFOS). It applies to ships built on or after 1 January 2026 and, through regulation II-2/1.2.10, to existing ships from the first survey on or after 1 January 2026. Removed PFOS foam must go to a shore reception facility. PFOS was used mainly in older film-forming foams. To check your foam, read the product data sheet and the supplier’s declaration, and ask the lab to state PFOS content in the analysis if in doubt. The SOLAS ban covers PFOS only; some ports and regions restrict other fluorinated foams, so check local rules before landing or using foam in port.
What the rules say
- MSC.1/Circ.1312, section 5, says the first periodical control of foam concentrate should be performed “not more than 3 years after being supplied to the ship, and after that, every year”.1
- MSC.1/Circ.1312, section 4, requires the periodical tests (sedimentation, pH, expansion ratio, drainage time and volumic mass, plus fire and stability tests for protein-based alcohol-resistant concentrates) to be carried out at laboratories or authorised service suppliers acceptable to the Administration.1
- MSC.1/Circ.1312, paragraph 4.7 and section 5, requires protein-based alcohol-resistant concentrates to pass a chemical stability test with acetone before delivery to the ship and annually thereafter.1
- MSC.1/Circ.1312, section 2, sets the sample size for periodical controls at 2 litres, stored in filled containers.1
- MSC.1/Circ.1432, paragraph 6.2, calls for a quarterly check that the proper quantity of foam concentrate is in the foam system storage tank.2
- MSC.1/Circ.1432, paragraph 7.4, calls for annual flow tests of water supply and foam pumps, with all piping “thoroughly flushed with fresh water after service”, and for samples of all foam concentrates to be tested under MSC.1/Circ.1312 (low expansion) or MSC/Circ.670 (high expansion).2
- MSC.1/Circ.1432, paragraph 9.2, calls for a five-yearly test of all foam proportioners to confirm the mixing ratio is within +30% to -10% of the nominal ratio defined by the system approval.2
- MSC.1/Circ.1432, paragraph 7.11, says sealed portable foam containers (excluding protein-based) less than 10 years old can normally be accepted without periodical tests, while protein-based ones more than five years old must be tested or renewed.2
- FSS Code chapter 14, paragraph 2.2.1.3, requires enough foam concentrate for at least 20 minutes of foam generation on tankers with inert gas and 30 minutes on tankers without.3
- FSS Code chapter 6, paragraph 4.1.1, and chapter 14, paragraph 2.2.1.4, forbid mixing different foam concentrate types and require the concentrate to be approved for the cargoes carried.3
- FSS Code chapter 6, paragraph 3.1.7, requires a means for the crew to safely check the quantity of concentrate and take periodic control samples.3
- SOLAS regulation II-2/10.11.2.2 states: “Use or storage of extinguishing media containing perfluorooctane sulfonic acid (PFOS) shall be prohibited.”4
Flag and class notes
- Marshall Islands (Marine Notice 2-011-14, Rev. Aug/2025) applies the Circ.1312 intervals, wants the tests done by laboratories or service suppliers acceptable to the RO, and requires the inspection records to include the age of foam concentrates and subsequent controls. It applies the PFOS ban to existing ships from the first Safety Equipment survey on or after 1 January 2026, referring to the unified interpretation in MSC.1/Circ.1694 (which deals with the threshold value for PFOS content).510
- Bahamas (Marine Notice 79, version 2.2, November 2025) added a section on the PFOS prohibition, including delivery of removed PFOS media to shore reception facilities.6
- Panama (Merchant Marine Circular MMC-281, October 2025) lists MSC.1/Circ.1312 and the medium and high-expansion circulars “only as recommendation”, while making MSC.1/Circ.1432 and 1318/Rev.1 the basis of its maintenance rules. Check whether your RO applies the Circ.1312 intervals as a survey requirement anyway; most survey checklists ask for the latest foam analysis.7
- At the periodical and renewal surveys under the Harmonized System of Survey and Certification (HSSC), the surveyor confirms that foam compounds have been checked and the distribution pipework proved clear.8
Key numbers
| What | Value |
|---|---|
| First foam analysis | Not more than 3 years after supply1 |
| Foam analysis after the first | Every year1 |
| Sample size | 2 litres, container filled1 |
| Type approval pH range | 6 to 9.5 at 20°C1 |
| Maximum sediment at type approval | 0.25% by volume, dispersible through 180 µm sieve1 |
| Tank quantity check | Quarterly2 |
| Proportioner tolerance (5-yearly test) | +30% to -10% of nominal mixing ratio2 |
| Proportioner tolerance (installation) | +30% to -0%3 |
| Sealed portable drums, non-protein | Accepted untested up to 10 years old2 |
| Sealed portable drums, protein | Test or renew after 5 years2 |
| Deck foam supply, tank deck | At least 0.6 l/min per m² (or 6 or 3 l/min per m², whichever is greater)3 |
| Deck foam duration | 20 min with inert gas, 30 min without3 |
| Monitor minimum output | 1,250 l/min3 |
| High-expansion foam, filling time | Largest space within 10 min3 |
| PFOS ban, existing ships | From first survey on or after 1 January 20264 |
What inspectors find
- Foam analysis reports missing or more than a year old, or a first analysis never done on concentrate older than three years.1
- Storage tanks well below the required quantity, often after foam was used in a drill or leaked through a passing valve, because the quarterly quantity check was skipped.2
- Tanks topped up with a different product without a compatibility approval, or a Type B concentrate on a chemical tanker trading polar cargoes that need Type A.3
- Old portable foam drums with no production date or with protein concentrate past five years and never tested.2
- In the 2012 Paris and Tokyo MOU fire safety campaign, “fire protection systems not maintained ready for use” was the most frequent negative answer (11% of Tokyo MOU inspections), and it covered foam systems along with all other fixed systems.9
FAQ
Who may take the foam sample?
The crew can take it, following the laboratory’s instructions, as long as the sample is representative. The tests themselves must be done by a laboratory or service supplier acceptable to the Administration (MSC.1/Circ.1312, section 4).
The lab says the foam is "not fit for further use". Do we have to replace all of it?
Yes, normally the whole charge in that tank must be replaced, because you cannot fix a degraded concentrate by adding new product, and mixing is only allowed for approved compatible products. Report it to the company and your RO, and arrange the replacement and disposal.
Is fluorine-free foam allowed?
Yes, if it is approved for the system and the cargoes. The FSS Code requires the concentrate to be approved by the Administration under the relevant IMO guidelines. Changing to a different concentrate may also mean checking the proportioners and the system approval.
Our foam is AFFF bought in 2015. Does the PFOS ban affect us?
Probably not, because PFOS was largely phased out of new foam before then, but you must be sure. Check the safety data sheet and ask the supplier or lab to confirm that it contains no PFOS. If it does, it has to be landed by the first survey on or after 1 January 2026.
Quiz6 questions
Sources
- 1
IMO MSC.1/Circ.1312, Revised guidelines for the performance and testing criteria, and surveys of foam concentrates for fixed fire-extinguishing systems (10 June 2009, corrected by MSC.1/Circ.1312/Corr.1), annex, sections 1.2, 2, 3.3, 3.5, 4 and 5. https://www.register-iri.com/wp-content/uploads/MSC.1-Circ.1312.pdf
- 2
IMO MSC.1/Circ.1432, Revised guidelines for the maintenance and inspection of fire protection systems and appliances (31 May 2012), as amended by MSC.1/Circ.1516 (8 June 2015), annex, paragraphs 5.3, 6.2, 7.4, 7.11 and 9.2 (consolidated copy annexed to Cayman Islands Shipping Notice 01/2014 Rev 2). https://www.cishipping.com/system/files/notices/documents/CISN%202014_01%20Rev%202%20with%20Annex.pdf
- 3
International Code for Fire Safety Systems (FSS Code), chapter 6 as replaced by resolution MSC.327(90) (ships constructed on or after 1 January 2014), paragraphs 3.1.1, 3.1.7, 3.1.19, 3.4.2 and 4.1; and chapter 14 (fixed deck foam systems, revised for ships constructed on or after 1 July 2014), paragraphs 2.2.1 and 2.2.2. Resolution MSC.327(90): https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.327(90).pdf
- 4
IMO Resolution MSC.532(107), Amendments to SOLAS 1974 (adopted 8 June 2023, in force 1 January 2026), annex, regulations II-2/1.2.10 and II-2/10.11. https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.532(107).pdf
- 5
Republic of the Marshall Islands Maritime Administrator, Marine Notice 2-011-14 (Rev. Aug/2025), sections 7 and 12. https://www.register-iri.com/wp-content/uploads/MN-2-011-14.pdf
- 6
Bahamas Maritime Authority, Marine Notice 79, Firefighting Equipment, version 2.2 (20 November 2025), section 12. https://www.classnk.or.jp/hp/pdf/activities/statutory/solas/solas_treaty/fire_protection/circular/ci_fi_bahama.pdf
- 7
Panama Maritime Authority, Merchant Marine Circular MMC-281, Guidelines for the maintenance, inspection of fire-protection system and appliances (October 2025), references. https://flagadmin.com/upload/userfiles/Panama/MMC-281-OCTOBER-2025-CM.pdf
- 8
IMO Resolution A.1186(33), Survey guidelines under the Harmonized System of Survey and Certification (HSSC), 2023 (adopted 6 December 2023), annex, (EP) 1.3.2.2. https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/AssemblyDocuments/A.1186(33).pdf
- 9
Tokyo MOU, Report of the 2012 Concentrated Inspection Campaign (CIC) on Fire Safety Systems (November 2013), section 3, question 5a. https://www.tokyo-mou.org/wp/wp-content/uploads/Final-Tokyo-MOU-Report-FSS-CIC-public-web-site.pdf
- 10
Liberian Registry, IMO MSC 110 meeting summary (2025), unified interpretations: MSC.1/Circ.1694 (PFOS restrictions, threshold value), effective 1 January 2026. https://www.liscr.com/marketing/liscr/media/liscr/online%20library/maritime/msc-110-meeting-summary.pdf
Rules checked 20 October 2026. VSL Safety is not an approved training provider and doesn't issue certificates. These lessons don't replace STCW training, or the manufacturer's training and certification that service technicians need.
