Start hereRules checked 20 October 2026
Cold water kills faster than drowning. An insulated immersion suit keeps a person’s core temperature from dropping more than 2 °C over six hours in near-freezing water, but only if water stays out. That depends on two things the crew cannot see from the outside of the bag: a zip that runs freely, and seams whose glue has not aged.
Inspectors keep finding the same faults. From 1 January 2023, immersion suit defects made up nearly a third of all life-saving deficiencies in the Marshall Islands’ flag State inspections. Stiff or broken zips were the biggest single cause, failed seams the next, followed by holes, missing lights or whistles and overdue air pressure tests. This lesson gives you the IMO inspection routine step by step, the air test that finds bad seams, and how different flags handle older suits.
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In this lesson
- Monthly inspection: immersion suits in the crew locker
- In plain words
- In detail
- What the rules say
- Flag and class notes
- Key numbers
- What inspectors find
- Quiz: 6 questions
Try it
Monthly inspection: immersion suits in the crew locker
In plain words
An immersion suit is a waterproof one-piece suit with feet, gloves and a hood that you climb into over your clothes before you abandon ship. Some keep you warm on their own; others must be worn with warm clothes underneath. Some float you face up on their own; others need a lifejacket on top. Cargo ships carry one for every person on board.
An anti-exposure suit is a lighter, more flexible suit for the people who crew the rescue boat or run the evacuation system, so they can work while wearing it. A thermal protective aid is a foil-like bag kept in liferafts and lifeboats to wrap survivors in.
Once a month the crew take each suit out, look it over, run the zip up and down, lubricate it with the maker’s product and put it back with the zip open. Every three years each suit is pumped up with low-pressure air and the seams are painted with soapy water to find leaks. Old suits are tested more often.
In detail
Who needs which suit
- Cargo ships: an immersion suit to LSA Code section 2.3 for every person on board, plus extra suits at watch or work stations far from where suits are normally kept (SOLAS III/32.3, in force since 1 July 2006 for new ships and from the first safety equipment survey after that date for existing ones). Ships other than bulk carriers that trade constantly in warm climates may be exempted by the flag.1
- Rescue boat crew and marine evacuation system (MES) party, all ships: an immersion suit or anti-exposure suit of an appropriate size for each person, unless the flag considers the ship constantly in warm climates.7
- Survival craft: thermal protective aids in every liferaft for 10% of the persons it may carry, or two, whichever is greater.4
What the LSA Code requires
| Item | Immersion suit (LSA 2.3) | Anti-exposure suit (LSA 2.4) |
|---|---|---|
| Donning | unpacked and on without help within 2 min, including lifejacket if needed6 | within 2 min4 |
| Coverage | whole body except the face; gloves permanently attached if separate6 | whole body except, if the flag allows, the feet; hood and gloves permanently attached6 |
| Jump | from 4.5 m without damage or injury, and no undue water ingress4 | from 4.5 m feet first4 |
| Thermal | uninsulated: core temperature falls no more than 2 °C in 1 h in 5 °C water; insulated: no more than 2 °C in 6 h in 0 to 2 °C water4 | core temperature falls no more than 1.5 °C per hour after the first 0.5 h in 5 °C water6 |
| Buoyancy | mouth at least 120 mm clear of the water; face down to face up in not more than 5 s6 | at least 70 N inherent buoyancy; face up in not more than 5 s4 |
| Other | buoyancy loss no more than 5% after 24 h; marked if it must be worn with a lifejacket, which goes over the suit6 | pocket for a portable VHF; lateral vision at least 120°4 |
These are the requirements of the LSA Code as amended by MSC.207(81), in force since 1 July 2010.6
A thermal protective aid must be made of waterproof material with a thermal conductance of not more than 7,800 W/(m²·K), cover the whole body of a person wearing a lifejacket except the face, be easy to put on without help in a survival craft, be removable in the water in not more than 2 min, and work from -30 °C to +20 °C.4
The monthly inspection (MSC/Circ.1047)
SOLAS III/20.7 requires a monthly inspection of life-saving appliances. The IMO guidelines for immersion and anti-exposure suits set out eight steps:2
- Check the bag closures and general condition so the suit comes out easily; make sure the donning instructions are legible; confirm the suit is the type and size marked on the bag.
- Lay the suit on a clean, flat surface; make sure it is dry inside and out; look for damage. Rips, tears or punctures are repaired to the maker’s instructions by a suitable repair station.
- Slide the zip up and down. Lubricate the front and back of the zip and the slide with the lubricant the maker recommends. If the zip does not work, take the suit out of service and discard it or return it to the maker or a suitable repair station.
- If fitted, check the inflatable head support or buoyancy ring and its hose; at least quarterly, inflate it and test it for leaks.
- Check the retro-reflective tape for condition and adhesion.
- Check the whistle and the expiry date of the light and battery.
- Put the suit back in its bag with the zip fully open.
- Use the opportunity for crew to practise putting the suits on.
A “suitable repair station” is one authorized by the suit maker and/or acceptable to the Administration.2
Vacuum-packed suits
Some makers supply suits sealed in clear airtight bags. The UK accepts a monthly check of the bag and the visible parts of the suit, to the maker’s instructions, instead of unpacking it, provided the bag is transparent and strong, can be opened easily, enough unpacked suits are kept for drills, and suits are unpacked and inspected under MSC/Circ.1047 if the bag is damaged or in doubt. If one packed suit is found defective, a further 25% are unpacked and inspected; any further fault means all are inspected.9 Liberia accepts vacuum packs on similar conditions.5
The air pressure test (MSC/Circ.1114)
The monthly look does not find seams and zips whose adhesive has aged. MSC/Circ.1114 recommends that each suit be air tested at intervals not exceeding three years, “or more frequently for suits over ten years of age”:3
- Fit a head piece with an air inlet into the face opening and secure it to limit leakage. Fit a low-pressure gauge. If gloves or boots are detachable, seal the wrists or cuffs with a short plastic pipe and clamps.
- Close the zip fully and any face flap. Inflate the suit to 0.7 to 1.4 kPa (0.1 to 0.2 psi). Inflate any auxiliary buoyancy through its oral valve to 0.7 kPa or until firm.
- Brush soapy water over every seam and closure, and over the seams, oral tube, attachment points and valves of the auxiliary buoyancy.
- Mark any area where bubbles form. Clean the suit with fresh water, dry it and have it repaired to the maker’s instructions.
The circular recommends doing the test at a shore facility able to make repairs with the maker’s instructions, parts and adhesives, but allows it on board if suitable equipment is available.3
What the rules say
- SOLAS regulation III/32.3.2, as replaced by MSC.152(78), requires an immersion suit complying with LSA Code section 2.3 for every person on board a cargo ship.1
- SOLAS regulation III/32.3.3 requires additional immersion suits at watch or work stations remote from the normal stowage, for the number of persons normally there.1
- SOLAS regulation III/7.3 requires an immersion suit or anti-exposure suit of an appropriate size for every person assigned to crew the rescue boat or the MES party.7
- LSA Code paragraph 2.3.2.2 requires an insulated immersion suit to limit the fall in body core temperature to 2 °C after 6 hours in calm circulating water at 0 °C to 2 °C.4
- LSA Code paragraph 2.3.1.1.1, as amended by MSC.207(81), requires an immersion suit to be unpacked and donned without assistance within 2 minutes.6
- LSA Code paragraph 4.1.5.1.24 requires thermal protective aids in each liferaft for 10% of its capacity or two, whichever is greater.4
- IMO guidelines MSC/Circ.1047 set the monthly inspection, including removing from service a suit whose zip does not work and quarterly leak tests of inflatable head supports.2
- IMO guidelines MSC/Circ.1114 recommend an air pressure test of seams and closures at 0.7 to 1.4 kPa at intervals not exceeding three years, or more often for suits over ten years old.3
Flag and class notes
The IMO text says only “more frequently” for suits over ten years old, so flags fill in the number. Check yours:
| Flag | Under 10 years | Over 10 years | Notes |
|---|---|---|---|
| United Kingdom (MGN 529) | every 3 years | every 2 years, and annual service at an authorized station | rules for airtight packaging9 |
| Liberia (SAF-007) | every 3 years | every other year | crew may test on board with the maker’s manual and test kit, trained crew and procedures in the safety management system (SMS), to the class surveyor’s satisfaction; “warm climates” defined as 32° N to 32° S5 |
| Cayman Islands (MACI 003/2007) | every 3 years | annually | test or repair by a station authorized by the maker; risk assessment for crew sizes8 |
- Marshall Islands. Marine Safety Advisory 08-23 asks owners to review their safety management system for MSC/Circ.1047 and 1114, to open and close zips over their whole length at each monthly check, and to tell the flag if serviceable suits fall below the number on the Safety Equipment Certificate.10
- Class surveyors check the condition of immersion and anti-exposure suits, their lights’ batteries, and the marking of suits that must be worn with a lifejacket at every annual survey.11
Key numbers
| What | Value |
|---|---|
| Donning time | 2 min unaided6 |
| Insulated suit thermal performance | core fall no more than 2 °C after 6 h in 0 to 2 °C water4 |
| Uninsulated suit thermal performance | core fall no more than 2 °C after 1 h in 5 °C water4 |
| Face-up turning time | not more than 5 s6 |
| Mouth clearance | at least 120 mm6 |
| Air pressure test pressure | 0.7 to 1.4 kPa (0.1 to 0.2 psi)3 |
| Air pressure test interval | not more than 3 years; more often over 10 years old3 |
| Head support leak test | at least quarterly2 |
| Thermal protective aids per liferaft | 10% of capacity or 2, whichever is greater4 |
| Share of RMI LSA deficiencies, 2023 | nearly one-third were immersion suits10 |
What inspectors find
- Defective or inoperable zips, the largest single group of immersion suit defects in Marshall Islands inspections.10
- Failed seams and holes in the suit material.10
- Missing or inoperative lights and whistles, and lights with expired batteries.1012
- Overdue air pressure tests, or no record of the last test on board.1012
- Fewer serviceable suits than the number on the Safety Equipment Certificate, for example after defective suits are taken out of service and no spares are carried.108
FAQ
Can the crew do the air pressure test?
MSC/Circ.1114 prefers a shore facility but allows testing on board with suitable equipment. Some flags, such as Liberia, set conditions: the maker’s service manual and test kit on board, trained crew, procedures in the SMS, and the test done to the satisfaction of the class surveyor. Repairs still go to an authorized station.
Should crew wear immersion suits inside a totally enclosed lifeboat?
Generally not. Liberia, citing IMO guidance in MSC.1/Circ.1278, notes that immersion suits are mainly for when the lifeboat cannot be boarded, and should not normally be worn when boarding a totally enclosed lifeboat.
Is an immersion suit also a lifejacket?
Only if it also meets the lifejacket requirements of LSA Code section 2.2. A suit that must be worn with a lifejacket is marked so, and surveyors check that marking.
What about the suits used for drills?
Keep enough unpacked suits for drills, especially if most are vacuum packed, and include them in the monthly inspection like the others.
Quiz6 questions
Sources
- 1
IMO Resolution MSC.152(78), Amendments to SOLAS (adopted 20 May 2004, in force 1 July 2006), new SOLAS regulation III/32.3 (Immersion suits). https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.152(78).pdf
- 2
IMO MSC/Circ.1047, Guidelines for monthly shipboard inspection of immersion suits and anti-exposure suits by ships’ crews (28 May 2002), Annex paragraphs 1 to 8 (copy published by the Indian Register of Shipping). https://www.irclass.org/media/6651/msc1-circ1047.pdf
- 3
IMO MSC/Circ.1114, Guidelines for periodic testing of immersion suit and anti-exposure suit seams and closures (25 May 2004), Annex paragraphs 1 to 4 (reproduced in NOAA Vessel Inspection Bulletin 04-10 Amendment 1). https://www.omao.noaa.gov/sites/default/files/documents/Vessel%20Inspection%20Bulletin%2004-10%20Amendment.pdf
- 4
LSA Code, IMO Resolution MSC.48(66), sections 2.3 (Immersion suits), 2.4 (Anti-exposure suits), 2.5 (Thermal protective aids) and paragraph 4.1.5.1.24. https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.48(66).pdf
- 5
Liberia Maritime Authority, Marine Notice SAF-007 Rev. 07/20, Lifesaving equipment: immersion suits and thermal protective aids, section 1. https://www.liscr.com/sites/default/files/online_library/SAF-007.pdf
- 6
IMO Resolution MSC.207(81), Amendments to the LSA Code (adopted 18 May 2006, in force 1 July 2010), amendments 6 to 21 (sections 2.3 and 2.4). https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.207(81).pdf
- 7
SOLAS chapter III, regulation 7.3 (Immersion suits and anti-exposure suits), as adopted by IMO Resolution MSC.47(66). https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/MSCResolutions/MSC.47(66).pdf
- 8
Cayman Islands Shipping Registry, Shipping Notice MACI 003/2007, The carriage, inspection and testing of immersion suits onboard Cayman Islands ships (May 2007), sections 2 and 3. https://cishipping.com/system/files/notices/documents/2007_03_CISN.PDF
- 9
UK Maritime and Coastguard Agency, MGN 529 (M+F), Life-Saving Appliances: Immersion Suits, Acceptance Criteria for Airtight Packaging (December 2014). https://assets.publishing.service.gov.uk/media/5a759cdee5274a545822cde4/MGN_529.pdf
- 10
Republic of the Marshall Islands Maritime Administrator, Marine Safety Advisory No. 08-23, Immersion suit defects (23 June 2023), as enclosed in Indian Register of Shipping Technical Circular 015/2023. https://www.irclass.org/media/6654/technical-circular-no15.pdf
- 11
IMO Resolution A.1186(33), Survey Guidelines under the HSSC, 2023, Annex items (EA) 1.2.2.31 and 1.2.2.32. https://wwwcdn.imo.org/localresources/en/KnowledgeCentre/IndexofIMOResolutions/AssemblyDocuments/A.1186(33).pdf
- 12
Indian Register of Shipping, PSC Annual Report 2024, life-saving appliance deficiencies, immersion suits. https://www.irclass.org/media/7954/psc-annual-report-2024.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.
