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Fixed fire systemsLesson 4 of 8

Water mist, sprinklers and water spray systems

You will know how water-based fire systems on ships are built and approved, and how to run the weekly to ten-yearly tests, including when failed sprinkler heads mean replacing a whole batch.

17 minutes · For signed-up learners, free · Rules checked 20 October 2026

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A sprinkler head is a small valve held shut by a glass bulb. It may hang over a cabin bed for twenty years, wet on the inside with stagnant water and exposed on the outside to steam, paint and cleaning sprays. On the day of a fire it has to open at the right temperature and spray the right pattern. Sprinkler heads that are corroded or clogged from the inside do not, and on ships that problem became serious enough for IMO to write a special testing procedure.

Water mist systems are now common in engine rooms, both as the main fixed system and as the local application system that sprays the hot spots on diesel engines and purifiers without stopping them. Ro-ro and car decks rely on large water spray (drencher) systems. This lesson covers all three: how they are built, how they are approved, and how they are tested.

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The rest of this lesson, the interactive The annual sprinkler test on a seven-year-old cruise ferry and the quiz are open to signed-up learners. It's free, takes a minute, and opens every lesson in all 14 courses.

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In this lesson

  • Try it: The annual sprinkler test on a seven-year-old cruise ferry
  • In plain words
  • In detail
  • What the rules say
  • Flag and class notes
  • Key numbers
  • What inspectors find
  • Questions people ask
  • Quiz: 6 questions

Sources

  1. 1 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, new paragraph 6.5, revised paragraphs 3.4, 7.5 and 9.3 and the sprinkler test flow chart), annex, paragraphs 4.7, 5.4, 6.5, 7.5, 9.3 and 10.2 (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
  2. 2 International Code for Fire Safety Systems (FSS Code), chapter 8, Automatic sprinkler, fire detection and fire alarm systems, paragraphs 2.1 to 2.5 (resolution MSC.98(73), as amended). https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.98(73).pdf
  3. 3 IMO MSC/Circ.1165, Revised guidelines for the approval of equivalent water-based fire-extinguishing systems for machinery spaces and cargo pump-rooms (10 June 2005), annex, paragraphs 10 to 26; amended by MSC.1/Circ.1237, MSC.1/Circ.1269 and MSC.1/Circ.1386. https://www.register-iri.com/wp-content/uploads/MSC.1-Circ.1165.pdf
  4. 4 IMO Resolution MSC.99(73), revised SOLAS chapter II-2 (adopted 5 December 2000), regulation II-2/10.5.6, as amended by resolution MSC.338(91). https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.99(73).pdf
  5. 5 IMO Resolution MSC.555(108), Amendments to the FSS Code (adopted 23 May 2024, in force 1 January 2026), annex, chapter 7, new section 2.5. https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.555(108).pdf
  6. 6 Republic of the Marshall Islands Maritime Administrator, Marine Notice 2-011-14 (Rev. Aug/2025), sections 9 and 12. https://www.register-iri.com/wp-content/uploads/MN-2-011-14.pdf
  7. 7 Panama Maritime Authority, Merchant Marine Circular MMC-281 (October 2025), paragraphs 4.2.4 and 4.5.5. https://flagadmin.com/upload/userfiles/Panama/MMC-281-OCTOBER-2025-CM.pdf
  8. 8 Hong Kong Marine Department, Merchant Shipping Information Note 55/2023 (4 September 2023), on MSC.1/Circ.1430/Rev.3. https://www.mardep.gov.hk/en/msnote/pdf/msin2355.pdf
  9. 9 Tokyo MOU, Report of the 2012 Concentrated Inspection Campaign (CIC) on Fire Safety Systems (November 2013), section 3, question 7. https://www.tokyo-mou.org/wp/wp-content/uploads/Final-Tokyo-MOU-Report-FSS-CIC-public-web-site.pdf

Free awareness training. Al Safwan Marine is not an approved training provider, so no certificate is given, and these courses are not a qualification. They don't replace STCW training, manufacturer training or the certification technicians need for this work. The manufacturer's manual and your flag's rules always come first.

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