Fire systems on Ro-Ro passenger ship weather decks carrying vehicles: the 2026 IMO requirement and how to write the TOR

When a weather deck carrying vehicles must have a fixed fire-extinguishing system — the two dates that must be kept apart

The requirement that turns this into real work for an owner, a technical manager or a yard does not come from one document. It comes from two resolutions adopted together at the 108th session of IMO’s Maritime Safety Committee (MSC 108, 15–24 May 2024). Both are dated 23 May 2024, both were deemed accepted on 1 July 2025, and both enter into force on 1 January 2026.

• Resolution MSC.550(108) — Amendments to chapters II-2 and V of SOLAS 1974. This inserts a new sub-heading, “6.2 Fixed water-based fire-extinguishing system on weather decks intended for carriage of vehicles”, into SOLAS II-2/20, and retitles regulation 20 as “Protection of vehicle, special category, open and closed ro-ro spaces, and weather decks intended for the carriage of vehicles”. The former paragraph 6.2, on portable extinguishers, is renumbered 6.3.
• Resolution MSC.555(108) — Amendments to the International Code for Fire Safety Systems (FSS Code). This amends FSS Code chapter 7, on fixed water-spraying and water mist systems, and chapter 9, on fire detection and alarm systems, adding an entirely new section 7/2.5.

The point to get right from the outset is that every engineering number used to design this system is in MSC.555(108), not in MSC.550(108). SOLAS II-2/20.6.2.1 says only that the ship shall have fixed monitors and that the system “shall comply with the provisions of the Fire Safety Systems Code”. A TOR or tender document that cites only MSC.550(108) gives a bidder nothing to work from, and the reference is incomplete against the text.

The two dates that must be kept apart

• 1 January 2026. Ro-ro passenger ships constructed on or after that date must meet the full requirement — SOLAS II-2/20.6.2.1 and 20.6.2.2 together with the whole of FSS Code 7/2.5. The word “constructed” in SOLAS is governed by regulation II-2/1.2.1, read with II-2/1.3 for what counts as a similar stage of construction. In practical terms classification societies read this as the date the keel is laid or an equivalent stage of construction — not the delivery date and not the contract date.
• The first survey falling due on or after 1 January 2028. Passenger ships with vehicle spaces, special category spaces or ro-ro spaces constructed before 1 January 2026 — including those built before 1 July 2012 — must comply with paragraph 20.6.2.3 no later than the first survey on or after 1 January 2028. The text says “on or after”, not “after”, and “first survey” in practice means the first annual, intermediate or renewal survey, whichever falls due first.

For a fleet already trading in Thai waters and on international routes, the date with real budget consequences is the second one, not the first. Existing ships are caught by their own survey cycle, which may fall in early 2028 or late in the year. Working through each vessel’s survey calendar is therefore the first task, before any system design begins.

Which ships are caught, and how far ‘weather deck’ extends in the text

The first question to settle, before any thought about equipment, is whether a given ship is caught at all — and if so, which parts of the deck count as protected area. The text defines some of this and not all of it, and that gap is where genuine disagreement between an owner and a surveyor arises.

The definitions that do exist, in SOLAS chapter II-2 regulation 3

• Weather deck (3.50) — “a deck which is completely exposed to the weather from above and from at least two sides”.
• Ro-ro passenger ship (3.42) — a passenger ship with ro-ro spaces or special category spaces.
• Vehicle spaces (3.49) — cargo spaces intended for the carriage of motor vehicles with fuel in their tanks for their own propulsion.
• Open ro-ro spaces (3.35) — ro-ro spaces open at both ends, or open at one end and provided with natural ventilation through permanent openings of at least 10 per cent of the total side area.
• Closed vehicle spaces (3.13) — defined by exclusion, as vehicle spaces that are neither open vehicle spaces nor weather decks. That in itself confirms a weather deck is a different category from a closed vehicle space.

The phrase that is not defined, and has to be settled with the Administration

The composite phrase the text actually uses is “weather deck intended for the carriage of vehicles” — and that phrase is defined nowhere in either resolution. Both define “weather deck” alone. The scope of “intended for the carriage of vehicles” attaches to intended use, not to a physical line drawn in the regulation, and FSS Code 7/2.5.1.2 uses a second parallel phrase, “the area intended for vehicle storage”.

The practical consequence is that a deck used for vehicles on some voyages and not others, a deck carrying only crew vehicles, or a deck where vehicles alternate with containers, all have to be settled with the flag Administration and the classification society. It is not for the designer or the equipment supplier to decide alone. This page therefore draws no fixed line about which decks are caught, because the text does not draw one.

Two different ship scopes inside the same package

An easily missed point: this set of amendments uses two different scopes in the same body of work.

• FSS Code 7/2.5, which is where the full specification lives, is written narrowly — it applies to ro-ro passenger ships constructed on or after 1 January 2026.
• The retroactive provision in SOLAS II-2/20.6.1 is written more broadly — passenger ships with vehicle, special category or ro-ro spaces constructed before 1 January 2026.

These two phrases are not equivalent and should not be used interchangeably in a specification or a fleet assessment. Some passenger ships with vehicle spaces that are not classified as ro-ro passenger ships may be caught by the retroactive provision while falling outside the full FSS 7/2.5 specification.

New ships and existing ships fall under different requirements — the most commonly mistaken point

This is where a great deal of published material gets it wrong, and the mistake costs owners money: it leads to being quoted for a specification the flag Administration never required.

New ships, constructed on or after 1 January 2026 — the full specification

FSS Code 7/2.5 opens plainly: “The requirements of this paragraph shall apply to ro-ro passenger ships constructed on or after 1 January 2026.” SOLAS II-2/20 carries the parallel sentence for paragraphs 6.2.1 and 6.2.2. So the whole set of figures — the combined 2.0 L/min per square metre, the 8.0 m boundary, the 75 % of throw distance rule, the 40 m water supply length, and the 5.0 L/min per square metre nozzles — is tied to this group of ships alone.

Existing ships, constructed before 1 January 2026 — a much lighter requirement

Existing ships are caught by SOLAS II-2/20.6.2.3 alone, which asks for only three things:

1. Monitors positioned so as to protect the vehicles without obstruction as far as practicable.
2. That operation of the monitors is assured, by safe access ways or by remote control not impaired by a fire in the area that monitor protects.
3. That each monitor delivers not less than 1,250 L/min.

That is the whole of it. The new-ship figures — the 2.0 L/min per square metre density, the 75 % rule, the 40 m supply length — do not appear in 20.6.2.3 and are not imposed on existing ships. Material circulating in this market routinely applies the new-build figures to the existing fleet. It should not be accepted without being shown where in the text it comes from.

The FSS Code 7/2.5 specification, set out so it can be lifted straight into a TOR

This is the section a naval architect, marine engineer or superintendent can copy directly into a procurement specification. Every line below comes from FSS Code chapter 7, section 2.5 as adopted by Resolution MSC.555(108), and applies to ro-ro passenger ships constructed on or after 1 January 2026 only.

Three points that are commonly misread

1. The 2.0 L/min per square metre is a combined figure; the 1,250 L/min is per monitor. The text reads: “The combined capacity of all fixed monitors shall be minimum 2.0 L/min per square metre of the protected area, but in no case shall the output of any monitor be less than 1,250 L/min.” A surprising amount of published material swaps these two round, which throws the whole system size out.
2. The 75 % rule is directional, not a radius. The text refers only to the farthest extremity “forward of that monitor”. Writing a specification as a 75 % radius circle around each monitor does not match the text and produces the wrong monitor count.
3. The 8.0 m is measured horizontally from the vehicle storage area, and stops at the nearest vertical boundary if that comes first. It is not 8.0 m measured along a slope or a diagonal.

Indicative worked example: a weather deck 120 m long and 22 m wide

This example exists to show the method. Real figures must be calculated from the actual ship drawings and agreed with the classification society and the flag Administration. Every assumed value is flagged as such.

Assumed inputs

• A weather deck used for vehicle stowage, 120 m long and 22 m wide (assumed for this example).
• Superstructure boundaries on two sides, each with a run of wall within 8.0 m of the vehicle area, 60 m long and averaging 6 m high (assumed for this example).
• Monitor throw distance in still air, from the test report for the selected model, assumed at 60 m (this figure must come from the actual test report for the model offered; never assume it in real work).

Step 1 — the protected area as the text defines it

FSS 7/2.5.1 defines the protected area as the entire length and width of the weather deck. The wording about superstructure boundaries within 8.0 m is a duty to deliver water to them — it does not say that the vertical surface is added to the area on which the 2.0 L/min per square metre is calculated.

• Protected area as the text defines it = 120 × 22 = 2,640 m²
• Superstructure boundaries within 8.0 m, 60 m long and 6 m high each side, approximately 720 m² — this figure is used to check whether the monitors reach, not added to the area basis.

A note on an unsettled reading. This point is not settled in practice. Some designers add the 720 m² of vertical surface to the area basis as well. This example uses the literal reading — deck area only — and shows the effect of the other reading at the end of the section.

Step 2 — combined monitor capacity

• Minimum combined rate = 2.0 × 2,640 = 5,280 L/min
• Using monitors at the statutory floor of 1,250 L/min each, 5,280 ÷ 1,250 = approximately 4.2, so not fewer than 5 monitors on flow grounds.
• On the inclusive reading, the area basis becomes 3,360 m², the combined rate becomes 6,720 L/min, and the minimum count rises to 6.

Step 3 — check again on geometry, which usually governs the real count

• Forward distance one monitor may be credited with = 0.75 × 60 = 45 m
• Over a 120 m deck, firing fore to aft in one direction, positions along the length = 120 ÷ 45 = approximately 2.67, so not fewer than 3 positions along the length.
• But the 22 m width and the “stowed to maximum capacity” condition normally force monitors on both port and starboard, raising the count to 3 × 2 = 6 positions.
• The monitor count actually used is the greater of Step 2 and Step 3, not one or the other. In this example the two happen to converge at 6, which on a real ship they often do not.

Step 4 — sizing the water supply, where prices differ most

• The area strip under 7/2.5.5 = full width 22 m × 40 m length = 880 m²
• Simultaneous rate for that strip = 2.0 × 880 = 1,760 L/min
• The text adds a second floor: water supply capacity must be not less than that required by the largest monitor. In this example the monitors selected at Step 2 sit at the statutory floor of 1,250 L/min, so that floor does not yet bind, and the design figure is 1,760 L/min.
• But if the designer chooses fewer, larger monitors — say 3 at 2,500 L/min — the floor becomes 2,500 and the design figure changes to 2,500 L/min instead. The size of the water supply therefore depends on which monitor is selected, not on deck area alone.

What this means for a tender

If a TOR does not state whether the protected area includes superstructure boundaries within 8.0 m, a bidder counting deck area only arrives at 2.0 × 2,640 = 5,280 L/min while one counting the boundaries arrives at about 6,720 L/min — a difference of roughly 27 per cent, from the same clause. And if the TOR does not fix the monitor size, the water supply floor moves with whichever model each bidder chooses. A bidder offering large monitors must offer a correspondingly large pump; one offering monitors at the statutory floor offers a smaller pump. Those two bids cannot be compared at all, though both will claim compliance with the same requirement. This is why a TOR must fix the area basis and the per-monitor rate from the outset.

Coverage and monitor placement studies on the actual general arrangement are work that belongs before the specification is locked, not after.

Water supply, isolation valves and interaction with the ship’s fire pumps

FSS 7/2.5.5 requires the system to be immediately available and capable of continuous discharge, and permits the water to come from more than one source: the ship’s fire main, pumps serving other fixed fire-fighting systems, or a dedicated seawater pump.

That flexibility is where retrofit projects either save money or lose it. Three points decide which.

The pumps must allow isolated or simultaneous operation. The arrangement has to permit the fire main and the deck monitors to run either independently or together, with adequate pressure for both. A design that can feed the monitors only by starving the fire main will not pass plan approval — and on an existing ship this is the constraint that most often forces a new pump rather than a tie-in.

Pressure at the monitor, not at the pump, is what matters. Throw distance is a function of nozzle pressure and flow. A monitor rated at a given throw in still air achieves it only at its rated pressure. Long runs of undersized pipe from an existing fire main will deliver flow but not pressure, and the coverage calculation from Step 3 above then silently fails. Hydraulic calculation to the furthest monitor, at the design flow, is not optional.

Isolation valves have to be reachable during a fire. The same principle that puts monitors outside the area they protect applies to the valves that control them. A valve that can only be reached across the deck that is burning is not an operable valve.

On existing ships, this section is usually where the real cost sits — not in the monitors themselves, but in whether the existing pumps, mains and sea suctions can carry the additional simultaneous demand. That assessment should be done before any equipment is selected.

The 125 % drainage requirement, and where the rule allows water in place of steel

The same resolutions add two further groups of requirements on the weather deck. Neither is about the monitors themselves, but both have to be designed alongside them, and both are routinely forgotten until they become expensive rework.

Drainage sized at 125 %

SOLAS II-2/20.6.2.2, for ro-ro passenger ships constructed on or after 1 January 2026, requires that where a fixed water-based system is fitted to cover a weather deck used for vehicles, drainage shall be provided and sized for not less than 125 % of the combined capacity of both the monitors and the required number of fire hose nozzles.

The reasoning behind this is not fire-fighting; it is stability. Water lying as a sheet on an open deck creates a free surface effect, which reduces metacentric height and can heel the ship dangerously. The more water discharged, the more must drain away, and the more margin is needed.

The point most often computed wrongly is the basis. The text says to calculate from the combined capacity of the monitors plus the required fire hose nozzles — not from the size of the water supply as designed. Those are not the same figure, and using the supply capacity gives an answer that is too low.

A simple worked figure, using the numbers from the calculation section above: with six monitors at 1,250 L/min each, the combined monitor capacity is 7,500 L/min, so drainage must handle not less than 1.25 × 7,500 = 9,375 L/min for the monitor portion alone, before adding the fire hose nozzle portion at the actual rating of the nozzles fitted to that ship.

A caution that follows: for a weather deck the minimum rate is already fixed at 2.0 L/min per square metre by FSS 7/2.5.2. The drainage load therefore has a floor that no technology choice can go below for this duty. The argument that a system using less water needs less drainage applies to enclosed spaces where the discharge rate is not fixed; it does not apply to an open weather deck. If a bidder offers that reasoning for weather deck work, ask them to point to the clause that supports it.

Safety distances on deck, and the option the rule offers

SOLAS II-2/20.5.3, a new provision on the arrangement of weather decks used for vehicles, sets three distances.

• More than 6.0 m — the horizontal safety distance from the designated vehicle stowage area to accommodation, control stations and service spaces that are normally manned, in adjacent superstructures and deckhouses.
• Reduced to 3.0 m where all boundaries within 6.0 m, including windows and doors, have A-60 fire integrity.
• More than 12.0 m — for survival craft, their embarkation stations, and access to those stations.

And here is the sentence that carries the most weight in this whole section. Paragraph 20.5.3.3 offers an alternative: an “A-0” boundary protected by a water-based system delivering not less than 5.0 L/min per square metre may be accepted as equivalent.

In other words, the rule itself offers water in exchange for steel. Cooling a boundary with water at 5.0 L/min per square metre on an A-0 boundary is accepted in place of upgrading the structure to A-60 — which on a retrofit is usually less disruptive structurally, shorter in yard time, and easier to demonstrate. The caution is that the 5.0 L/min per square metre in this clause is a different thing from the 5.0 L/min per square metre for nozzles covering areas monitors cannot reach under FSS 7/2.5.4. The two figures happen to be equal but do different jobs. Do not merge them into one line in a specification.

Companion requirements in the same resolutions: detection, CCTV and photoluminescent signage

An owner budgeting for a single yard visit should know that these resolutions add more than the deck system. Several other requirements share the same dates — 1 January 2026 for new ships, first survey on or after 1 January 2028 for existing ones. Combining them into one package is cheaper than doing them piecemeal.

Fire detection

• SOLAS II-2/20.4.1.1 requires detection of both smoke and heat throughout vehicle spaces, special category spaces and ro-ro spaces, and permits the Administration to accept a linear heat detector for the heat detection duty.
• Paragraph 20.4.1.6 applies the same requirement to passenger ships constructed before 1 January 2026.
• Paragraph 20.4.3.1 requires an efficient fire patrol in special category spaces.

Detector spacing under the amended FSS Code 9/2.4.2.2

For linear heat detectors, the text requires spacing not exceeding 9.0 m and not more than 4.5 m from a bulkhead, tested to EN 54-22:2015 together with IEC 60092-504.

CCTV with immediate playback

SOLAS II-2/20.4.4 is entirely new. It requires a CCTV system with immediate playback, cameras mounted high enough to see over vehicles stowed to full capacity, and playback retrievable from a continuously manned control station or the safety centre, retaining recordings for:

• not less than 7 days on ships constructed on or after 1 January 2026
• not less than 24 hours on existing ships

Photoluminescent signage

SOLAS II-2/20.7, also new, requires section identification signage for the fixed water-spraying system in photoluminescent material on newly constructed ships.

All of this bears directly on crew readiness. A system that is fully installed but that nobody is confident enough to operate in the first thirty seconds delivers no more than having no system at all. Drills and training should be planned alongside the installation, not after it.

What to write into a TOR so that bids can be compared

The questions a bidder cannot answer are the ones that become variation orders later. This list is written to be lifted into a specification.

A. The design basis

• State one base standard and its edition. Cite SOLAS II-2/20.6.2 (Res. MSC.550(108)) and FSS Code 7/2.5 (Res. MSC.555(108)) together — citing the SOLAS resolution alone gives the bidder no figures.
• State whether the ship is a new build under the full specification or an existing ship under 20.6.2.3. These are different scopes of work and should never be priced against the same clause list.
• Fix the protected area basis. State explicitly whether superstructure boundaries within 8.0 m are included in the area on which the 2.0 L/min per square metre is calculated, or treated only as a coverage duty. Without this, bids differ by roughly a quarter for no reason a buyer can see.

B. Monitors

• Require the still-air throw distance for the model offered, from a test report, with the nozzle type, working pressure and elevation angle at which it was measured. This is the figure the 75 % rule turns on, and no layout can be checked without it.
• Fix the minimum flow per monitor at 1,250 L/min and state the combined figure required.
• Require the coverage calculation to be presented directionally, as the text is written — the farthest extremity forward of each monitor — not as a radius.
• Require the layout to be demonstrated with vehicles stowed to maximum capacity, since that is the condition the text sets.

C. Water supply and drainage

• Require the hydraulic calculation to the furthest monitor at design flow, showing pressure at the monitor, not at the pump.
• Require confirmation that the fire main and the monitors can run isolated or simultaneously with adequate pressure for both.
• Require the drainage calculation to be based on 125 % of combined monitor plus required hose nozzle capacity, and to state the figures used.

D. Evidence

• Require type approval or plan approval documentation naming the model offered, and state that certificates covering a different model or a different configuration will not be accepted.
• Require the commissioning test procedure to be submitted with the bid, not after award.

E. The companion items

• State whether detection, CCTV and photoluminescent signage are in scope, and if so require them to the same clause references, so that one contractor is responsible for the interfaces.

The most common errors in documents circulating in this market

Collected from material currently in circulation. Each one is a real error with a real cost.

Citing a regulation number that does not exist. There is no SOLAS regulation II-2/20-2. The operative provisions are II-2/20.6.2 and FSS Code 7/2.5.

Swapping the two flow figures. The 2.0 L/min per square metre is the combined capacity of all monitors; the 1,250 L/min is the floor for any single monitor. Reversing them changes the system size entirely.

Applying new-ship figures to existing ships. Existing ships fall under 20.6.2.3, which requires unobstructed protection as far as practicable, safe access or protected remote operation, and 1,250 L/min per monitor. It does not impose the 2.0 L/min per square metre density, the 75 % rule or the 40 m supply length.

Treating the 75 % rule as a radius. It is directional — the farthest extremity forward of that monitor.

Quoting the throw distance from a brochure rather than a test report. Throw depends on nozzle type, flow and pressure, discharge medium, throw angle and mounting height. A single number without those conditions stated cannot be used for a layout.

Confusing the two 5.0 L/min per square metre figures. One is for nozzles covering areas monitors cannot reach (FSS 7/2.5.4). The other is the boundary cooling equivalence for an A-0 boundary (SOLAS II-2/20.5.3.3). Same number, different duties.

Computing the 125 % drainage from supply capacity. The basis is combined monitor plus required hose nozzle capacity.

Presenting this as a water mist requirement. FSS Code 7/2.5 specifies monitors and performance figures. It does not name a technology, and no technology claim substitutes for the flow, throw and distribution evidence.

The PFOS foam requirement is a separate instrument — do not confuse them

More than one IMO requirement falls due around 2026, and two of them are frequently swapped in owners’ internal documents, although they are different instruments, different duties and different budgets.

Neither substitutes for the other, and neither makes the other go away. One ship may have to do both in the same docking, but they are two separate work items technically, documentarily and contractually. The error we see is combining them into a single budget line and then under-pricing one of them.

This page covers the first only.

Primary sources

Everything on this page is drawn from the following. Where a figure could not be verified against a primary text, it is not stated here.

Regulation

• Resolution MSC.550(108) — Amendments to chapters II-2 and V of SOLAS 1974, adopted 23 May 2024, in force 1 January 2026.
• Resolution MSC.555(108) — Amendments to the FSS Code, adopted 23 May 2024, in force 1 January 2026. Introduces FSS Code 7/2.5 and amends chapter 9.
• SOLAS chapter II-2 consolidated text, for the definitions in regulation 3 and for regulation 1.2.1 read with 1.3 on what “constructed” means.

Other standards referenced

• NFPA 750 for the definition of water mist pressure classes.
• EN 54-22:2015 and IEC 60092-504 for linear heat detector testing, as referenced by the amended FSS Code chapter 9.

A note on what is not cited here. No manufacturer’s throw distance, type approval number or performance figure appears on this page. Those belong to a specific product and should be supplied by the bidder with the test report behind them.

SATU Innovative and Ro-Ro weather deck fire systems in Thailand

This page is a regulatory reference document, not a product page. It names no brand, because what determines whether a system passes is the text and the certificates, not the manufacturer’s name.

What we do. SATU Innovative works on the engineering and procurement side: reading the requirement against the correct edition, converting it into a specification that can be verified on acceptance, calculating monitor count and placement from the throw distance a manufacturer will certify, checking whether the certificates a bidder submits actually cover the model and configuration being offered, and writing the checklist for the acceptance test.

What we do not claim. We are not the distributor of any fire monitor brand for this duty, and we do not claim to be. When a manufacturer provides certification and verifiable throw figures, we will publish that information with its source stated.

If you are writing a TOR for a weather deck, or working out what an existing ship has to do before its first survey, talk to our engineers with the ship type, keel-laying date, deck dimensions and the general arrangement you have.

Frequently asked questions

When does the IMO requirement for fire systems on weather decks carrying vehicles take effect?

Two resolutions adopted together at MSC 108 on 23 May 2024 govern it: Resolution MSC.550(108), amending SOLAS chapters II-2 and V, and Resolution MSC.555(108), amending the FSS Code. Both enter into force on 1 January 2026. Ro-ro passenger ships constructed on or after that date must meet the full specification in FSS Code 7/2.5. Passenger ships with vehicle, special category or ro-ro spaces constructed before that date fall under the lighter SOLAS II-2/20.6.2.3, no later than the first survey falling due on or after 1 January 2028.

Our ship was built in 2015 and has a weather deck used for vehicles. What do we have to do, and by when?

You fall under SOLAS II-2/20.6.2.3, not under the full FSS 7/2.5 specification, and the deadline is the first survey falling due on or after 1 January 2028. That provision requires three things only: monitors positioned to protect the vehicles without obstruction as far as practicable; assurance that they can be operated, by safe access ways or by remote control not impaired by a fire in the area protected; and not less than 1,250 L/min from each monitor. The 2.0 L/min per square metre density, the 75 % throw rule and the 40 m supply length do not apply to your ship. If a bidder quotes you against those figures, ask which clause imposes them.

Is the 2.0 L/min per square metre a per-monitor figure or a combined figure?

Combined. The text reads that the combined capacity of all fixed monitors shall be minimum 2.0 L/min per square metre of the protected area, but that in no case shall the output of any monitor be less than 1,250 L/min. So the density is a system-level figure and the 1,250 L/min is a per-monitor floor. A good deal of circulating material reverses these two, which throws the whole system size out.

How many monitors are required? Is there a table based on the beam of the ship?

There is no table. The count is whichever is greater of two independent calculations. The first is flow: combined capacity of at least 2.0 L/min per square metre of protected area, with no monitor below 1,250 L/min. The second is geometry: the distance from each monitor to the farthest extremity of the protected area forward of it must not exceed 75 % of that monitor’s still-air throw distance, with vehicles stowed to maximum capacity. On most ships geometry governs, and the beam usually forces monitors on both sides.

How is the 75 % of throw distance rule calculated so that it matches the text?

Directionally, not as a radius. FSS 7/2.5.3 refers to the distance from a monitor to the farthest extremity of the protected area forward of that monitor. Drawing a 75 % radius circle around each monitor does not match the text and produces the wrong count. The throw distance itself must come from the test report for the model offered, stating nozzle type, working pressure and elevation angle — a single brochure number without those conditions cannot be used.

Can we feed the deck monitors from the ship’s existing fire pumps?

FSS 7/2.5.5 permits the water to come from the ship’s fire main, from pumps serving other fixed fire-fighting systems, or from a dedicated seawater pump. But the arrangement must allow the fire main and the monitors to run either isolated or simultaneously with adequate pressure for both. In practice the binding question on an existing ship is not flow but pressure at the monitor, since throw distance depends on it. A hydraulic calculation to the furthest monitor at design flow will tell you whether a tie-in works or whether a new pump is needed, and that assessment should come before any equipment is selected.

Can low-pressure water mist be used instead of monitors on the weather deck?

That is not the right way to frame it, and the misunderstanding is common. FSS Code 7/2.5 calls for fixed monitors delivering a stated flow, positioned to satisfy the throw-distance rule. What must be demonstrated to a classification society is flow rate, throw distance and uniform distribution — not the name of a technology. The weather deck is monitor work. Water mist is the answer for enclosed spaces on the same ship, under different approval routes entirely.

Can MSC.1/Circ.1430 be cited for the weather deck?

No. MSC.1/Circ.1430/Rev.3 covers closed vehicle decks, ro-ro spaces and special category spaces — enclosed spaces. The open weather deck is governed by SOLAS II-2/20.6.2 and FSS Code 7/2.5, which are regulation rather than guidance. Citing the circular for a weather deck duty points at the wrong instrument and at a different space type, and it is one of the more common errors in documents circulating in this market.