Start hereRules checked 20 October 2026
Every fixed system in this course depends on someone knowing there is a fire. In a manned engine room or a busy galley, people may see it. In a cabin at 3 a.m., an unattended engine room, a container hold or a cable trunk, the fire detection system is the only witness. The sooner it raises the alarm, the smaller the fire the crew has to fight.
Detection systems also fail in quiet ways: a detector covered with a plastic bag during painting, a loop isolated after a false alarm and never restored, a smoke detector in a galley that keeps going off. On the cruise ship Edinburgh Castle in 1998, the galley’s detection loop had been isolated after a fault, and the fire was found by a patrol. This lesson covers where detectors go, how the system must behave, and how to test it.
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In this lesson
- Which detection fits the space?
- In plain words
- In detail
- What the rules say
- Flag and class notes
- Key numbers
- What inspectors find
- Quiz: 6 questions
Try it
Which detection fits the space?
In plain words
A fire detection system has four parts:
- Detectors that sense smoke, heat or flame.
- Manual call points: the red “break glass” or “press here” boxes, so anyone who sees a fire can raise the alarm.
- A control panel, on the bridge or in the fire control station, that shows where the alarm came from and sounds a signal. If no one acknowledges it within two minutes, it sets off the alarm throughout the crew areas.
- Cables, power supplies and batteries that keep it working even in a blackout, and tell you if a wire is broken.
Detectors are chosen for the space. Smoke detectors find most fires earliest, so they are used in cabins, corridors and stairways. Where steam or fumes would set off a smoke detector all the time, like a galley, a laundry or a sauna, heat detectors are used. Flame detectors see the flicker of a flame and react in seconds, which suits engine room hot spots. Cargo holds use a different idea: a fan sucks air from each hold through small pipes to a sensor on the bridge, so the crew can see which hold the smoke comes from.
The system only works if every detector is tested with real smoke or heat, a few every month so all are done within five years, and nobody switches parts of it off and forgets.
In detail
Where detection is required (SOLAS II-2/7)
| Space | Requirement |
|---|---|
| Periodically unattended machinery spaces, and machinery spaces with remote control from a manned control room | Fixed fire detection and alarm system; systems using only heat detectors are not permitted except in spaces of restricted height |
| Accommodation, all ships | Smoke detectors in all stairways, corridors and escape routes |
| Passenger ships > 36 passengers | Smoke detection in service spaces, control stations and accommodation, including corridors and stairways (with sprinklers under SOLAS II-2/10.6.1) |
| Cargo ships, method IC | Smoke detection in corridors, stairways and escape routes |
| Cargo ships, method IIC | Sprinkler, fire detection and alarm system in accommodation and service spaces, plus smoke detection in corridors, stairways and escape routes |
| Cargo ships, method IIIC | Detection in all accommodation and service spaces, plus smoke detection in corridors, stairways and escape routes |
| Cargo spaces | Detection or sample extraction in cargo spaces of passenger ships not accessible; required for dangerous goods (II-2/19.3.3) and vehicle and ro-ro spaces (II-2/20.4) |
| Manual call points | Throughout accommodation, service spaces and control stations; one at each exit; no point in a corridor more than 20 m from a call point |
How the system must behave (FSS Code chapter 9)
- Two power supplies, one of them an emergency source, through an automatic change-over switch near the panel; for ships built from 1 July 2014, a change-over or a single supply failure must not cause loss of detection. At the end of the emergency period, the system must still run all alarm signals for at least 30 minutes.
- Alarm sequence: a detector or call point gives a visual and audible signal at the panel and indicating units; if not acknowledged within 2 minutes, an audible alarm sounds automatically throughout crew accommodation, service spaces, control stations and category A machinery spaces.
- Faults (open circuit, earth fault, wire-to-wire short) give a fault signal distinct from a fire signal.
- Disconnection: particular spaces may be disconnected, for example a workshop during hot work or a ro-ro space during loading, but the system must restore itself automatically after a set time, and the space must be manned or patrolled meanwhile.
- Sections: a section covering accommodation, service spaces or control stations must not include a category A machinery space or a ro-ro space. Passenger ships need individually identifiable detectors; cargo ships need at least section identification. Ships built from 1 July 2014 with a cargo control room need an additional indicating unit there.
- Detector performance: smoke detectors in stairways, corridors and escape routes operate before smoke density exceeds 12.5% obscuration per metre but not below 2%; heat detectors between 54°C and 78°C when temperature rises slower than 1°C per minute; up to 130°C in drying rooms and 140°C in saunas.
Detector spacing (FSS Code table 9.1)
| Detector | Max floor area per detector | Max distance between centres | Max distance from bulkheads |
|---|---|---|---|
| Heat | 37 m² | 9 m | 4.5 m |
| Smoke | 74 m² | 11 m | 5.5 m |
| Combined smoke and heat (added for ships from 1 January 2026) | 74 m² | 9 m | 4.5 m |
Detectors go on the deckhead at least 0.5 m from bulkheads (except in corridors, lockers and stairways), away from beams, ducts and air flows that would keep smoke away. In stairways they are at least at the top level and every second level below.
New from 1 January 2026 (resolution MSC.555(108)): for ships built on or after that date, linear heat detectors must be tested to EN 54-22:2015 and laid at most 9 m apart and 4.5 m from bulkheads; combined smoke and heat detectors get their own spacing row; and on new ro-ro passenger ships, alarms must follow a consistent presentation scheme, and only the smoke function in vehicle spaces may be disconnected during loading, with automatic reset. Heat detection and manual call points may not be disconnected.
Sample extraction smoke detection (FSS Code chapter 10)
Air is drawn by duplicate fans from smoke accumulators in each hold through sampling pipes of at least 12 mm bore to a control panel where the crew can see smoke in each pipe and a sensor alarms before 6.65% obscuration per metre. Accumulators are on the deckhead, no part of the overhead more than 12 m horizontally from one, with another in each exhaust ventilation duct. Where the pipes double as CO2 discharge lines, three-way valves switch them from the detector to the CO2 manifold. Sequential scanning systems must re-scan each point within 120 seconds. On installation, smoke at the most remote accumulator must give an alarm within 180 s on vehicle decks and 300 s in container and general cargo holds. The pipes must have a means of purging with compressed air.
Testing (MSC.1/Circ.1432 and SOLAS II-2/7.3)
| Interval | Test |
|---|---|
| Weekly | Lamp or indicator test on the fire detection and alarm panel |
| Monthly | Test a sample of detectors and manual call points so that all have been tested within five years (the Administration sets the sample for very large systems) |
| Annual | Test all fire detection systems, including those that release extinguishing systems automatically; visually inspect all accessible detectors for tampering or obstruction so all are seen within one year; test the emergency power change-over |
SOLAS II-2/7.3.2 requires tests with equipment producing hot air at the right temperature, smoke or aerosol of the right density and particle size, or other phenomena the detector responds to. In practice: a smoke aerosol cup on a pole for smoke detectors, a heat tool for heat detectors, a flame simulator for flame detectors, and real smoke at the far accumulator for sample extraction systems. Use the maker’s approved test equipment and procedure. Never test by spraying anything that leaves residue on the sensor. Detectors in cold rooms need procedures suited to the cold. Ships with self-diagnostic systems and a cleaning regime may test as the Administration requires.
Log each test with the detector address or location, date, result and any detector replaced; an addressable panel’s event log is a useful record but does not replace the test list.
What the rules say
- SOLAS regulation II-2/7.3.2 requires fixed fire detection and alarm systems to be “periodically tested” by equipment producing hot air, smoke or aerosol particles, or other phenomena to which the detector is designed to respond.1
- SOLAS regulation II-2/7.4.2 does not permit detection systems using only thermal detectors in periodically unattended machinery spaces, except in spaces of restricted height.1
- SOLAS regulation II-2/7.5.1 requires smoke detectors in all stairways, corridors and escape routes within accommodation spaces.1
- SOLAS regulation II-2/7.7 requires a manual call point at each exit and that no part of a corridor is more than 20 m from a manual call point.1
- FSS Code chapter 9, paragraph 2.5.1.1, requires an audible fire alarm throughout crew accommodation, service spaces, control stations and category A machinery spaces if a fire signal is not acknowledged within 2 minutes.2
- FSS Code chapter 9, paragraph 2.1.1, allows particular spaces to be disconnected only with automatic restoration after a predetermined time and with the space manned or patrolled.2
- FSS Code chapter 9, paragraph 2.4.2.2 and table 9.1, set the maximum spacing of heat detectors (37 m², 9 m apart, 4.5 m from bulkheads) and smoke detectors (74 m², 11 m apart, 5.5 m from bulkheads).2
- FSS Code chapter 9, as amended by resolution MSC.555(108), requires linear heat detectors on ships built on or after 1 January 2026 to be tested to EN 54-22:2015 and laid at most 9 m apart and 4.5 m from bulkheads.4
- FSS Code chapter 10, paragraph 2.4.2.2, requires a sample extraction system, when installed, to give an alarm within 180 s on vehicle decks and 300 s in container and general cargo holds after smoke is introduced at the most remote accumulator.3
- MSC.1/Circ.1432, paragraph 5.10, calls for monthly testing of a sample of detectors and manual call points so that all devices are tested within five years.5
- MSC.1/Circ.1432, paragraph 7.2, calls for annual testing of all detection systems, a visual inspection of all accessible detectors within one year, and a test of the emergency power supply change-over.5
Flag and class notes
- Bahamas (Marine Notice 79, version 2.2) says the monthly schedule should physically test alternating detectors each month; on very large systems (1,000+ detectors) at least one detector in each large compartment, or in each group of small compartments on the same deck and fire zone, and at least one on each cable line in each fire zone. Manual call points are tested with the detectors. Sample extraction systems should be fully tested every month, and before loading where laden voyages exceed one month.6
- Marshall Islands (Marine Notice 2-011-14, Rev. Aug/2025) lists the weekly, monthly and annual detection tests of MSC.1/Circ.1432 in its interval table and requires deficiencies and corrective actions to be recorded.7
- Class and IMO interpretations: IACS UI SC35 requires the alarm sounder system to have two power sources, one an emergency source, and IMO’s MSC.1/Circ.1433 clarifies that the IEC standard for detectors is IEC 60092-504. Under IACS UI SC271, a space with a cargo control console counts as a cargo control room even if it is not a dedicated one (for example a ship’s office or machinery control room), so it needs the additional indicating unit.2
- Combined detector spacing: IMO has issued a unified interpretation of the new spacing rule for combined smoke and heat detectors (MSC.1/Circ.1695, effective 1 January 2026). Ask your RO how it applies to your ship.10
- Surveys: HSSC survey guidelines have the surveyor examine and test, as feasible, the detection and sample extraction systems at the annual survey and test them at periodical and renewal surveys.8
Key numbers
| What | Value |
|---|---|
| Manual call point distance in corridors | No point more than 20 m away1 |
| Unacknowledged alarm to general crew alarm | 2 min2 |
| Smoke detector response (escape routes) | Above 2% and before 12.5% obscuration per metre2 |
| Heat detector response | Between 54°C and 78°C (rise < 1°C/min)2 |
| Heat detectors in drying rooms / saunas | Up to 130°C / 140°C2 |
| Heat detector spacing | 37 m², 9 m apart, 4.5 m from bulkheads2 |
| Smoke detector spacing | 74 m², 11 m apart, 5.5 m from bulkheads2 |
| Minimum distance from bulkhead | 0.5 m (not corridors, lockers, stairways)2 |
| Alarm signals after emergency period | At least 30 min2 |
| Sample extraction scan interval | Not more than 120 s3 |
| Sample extraction alarm time (installation test) | 180 s vehicle decks, 300 s cargo holds3 |
| All detectors and call points tested | Within 5 years (monthly sample)5 |
| All accessible detectors visually inspected | Within 1 year5 |
What inspectors find
- In the 2012 Paris and Tokyo MOU fire safety campaign, activating a detector or call point failed to give the required signal at the panel in 2.4% of Tokyo MOU inspections, and fire detection deficiencies were about 10% of all campaign deficiencies.9
- Loops or zones isolated after false alarms and never restored, often in galleys, laundries and engine rooms; the FSS Code requires automatic restoration after a set time.2
- Detectors covered with plastic or tape after painting or hot work, or removed and not replaced; detectors blocked by new ceilings or cable trays.5
- No record showing that every detector and call point has been tested within five years, or tests done only with the panel’s test button.5
- Sample extraction pipes blocked by dust or cargo residue, flow indicators not working, or the three-way valves left in the CO2 position.3
FAQ
Can I test smoke detectors with the panel's test button?
No. The panel lamp test (weekly) proves the indicators. SOLAS II-2/7.3.2 requires detectors to be tested with heat, smoke or aerosol of the right kind, so the sensing element and the path to the panel are both proven.
We do hot work in the engine room workshop. May we isolate the detectors?
Yes, the FSS Code allows a space to be disconnected, for example during hot work, but the system must restore automatically after a set time and the space must be manned or patrolled meanwhile. Record the isolation in the hot work permit.
Our ship is a cargo ship. Do we need addressable (individually identifiable) detectors?
Not by SOLAS: cargo ships need at least section identification. If an addressable system is fitted, the FSS Code requires that a fault in one section does not stop the remaining detectors from being identified, though isolator modules need not be fitted at every detector in cargo ships if the arrangement limits the effect of a fault.
How do we test a sample extraction system?
Introduce smoke at the accumulators (starting with the most remote), check that it appears at the right pipe in the control panel and that the alarm sounds, and check the airflow indication for each line. The Bahamas expects a full test every month.
Quiz6 questions
Sources
- 1
IMO Resolution MSC.99(73), revised SOLAS chapter II-2 (adopted 5 December 2000, in force 1 July 2002), regulation II-2/7 (Detection and alarm), paragraphs 3, 4, 5 and 7, as amended. https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.99(73).pdf
- 2
International Code for Fire Safety Systems (FSS Code), chapter 9 as replaced by resolution MSC.311(88) (ships constructed on or after 1 July 2012) and amended by resolutions MSC.339(91) and MSC.555(108), paragraphs 1.1, 2.1, 2.2, 2.3, 2.4 and 2.5; with IACS UI SC35 and SC271 and MSC.1/Circ.1433 and 1528. https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.311(88).pdf
- 3
International Code for Fire Safety Systems (FSS Code), chapter 10, Sample extraction smoke detection systems, as replaced by resolution MSC.292(87) (ships constructed on or after 1 January 2012), paragraphs 2.1.2, 2.2, 2.3 and 2.4. https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.292(87).pdf
- 4
IMO Resolution MSC.555(108), Amendments to the FSS Code (adopted 23 May 2024, in force 1 January 2026), annex, chapter 9, paragraphs 1.1, 2.3.1.5, 2.4.2.2 and 2.5.1.2 to 2.5.1.4. https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.555(108).pdf
- 5
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, annex, paragraphs 4.1, 5.10 and 7.2 (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
- 6
Bahamas Maritime Authority, Marine Notice 79, Firefighting Equipment, version 2.2 (20 November 2025), section 5. https://www.classnk.or.jp/hp/pdf/activities/statutory/solas/solas_treaty/fire_protection/circular/ci_fi_bahama.pdf
- 7
Republic of the Marshall Islands Maritime Administrator, Marine Notice 2-011-14 (Rev. Aug/2025), section 12 and Appendix A. https://www.register-iri.com/wp-content/uploads/MN-2-011-14.pdf
- 8
IMO Resolution A.1186(33), Survey guidelines under the Harmonized System of Survey and Certification (HSSC), 2023, annex, (EA) 1.2.2.9 and (EP) 1.3.2.4. 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 8 and deficiency analysis (code 07106). 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.1695 (FSS Code chapter 9, paragraph 2.4.2.2, spacing of combined smoke and heat detectors), 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.
