What to check on a Insulated Immersion Suit.
SOLAS distinguishes between an immersion suit and an insulated immersion suit by thermal performance, not by cut or material alone. Both are one-piece waterproof garments donned over normal clothing that give buoyancy and protect against immersion. An insulated immersion suit must, when tested on a person in calm circulating water at 5 degrees Celsius, limit the drop in the wearer's core body temperature to no more than 2 degrees Celsius after six hours; an ordinary (uninsulated) immersion suit is not required to meet this test and is instead normally issued…
What defines an insulated immersion suit
SOLAS distinguishes between an immersion suit and an insulated immersion suit by thermal performance, not by cut or material alone. Both are one-piece waterproof garments donned over normal clothing that give buoyancy and protect against immersion. An insulated immersion suit must, when tested on a person in calm circulating water at 5 degrees Celsius, limit the drop in the wearer's core body temperature to no more than 2 degrees Celsius after six hours; an ordinary (uninsulated) immersion suit is not required to meet this test and is instead normally issued together with a separate thermal protective aid. The practical difference is where the suit is carried: vessels operating on colder or longer-exposure routes are far more likely to carry the insulated type as standard.
Main components
Outer waterproof shell
A single-layer or laminated waterproof fabric, cut to allow a full range of movement, sealed at every seam so the suit stays airtight and watertight when worn correctly.
Insulation layer
Built-in thermal insulation, integral to the suit rather than added separately, is what allows the insulated type to meet the 2-degree core temperature test on its own.
Closure and face seal
A watertight zip, usually self-donning and reachable by the wearer without assistance, plus a face seal or hood that keeps water off the head and neck while leaving the airway clear.
Buoyancy and righting
Built-in buoyancy sufficient to turn an unconscious wearer face-up in the water within a defined time, combined with a light and, on suits intended for lifeboats, retro-reflective tape for visibility.
Hand and foot protection
Integral boots or foot pockets and either integral gloves or a means of protecting the hands, since bare-hand exposure is one of the fastest routes to incapacitation in cold water.
Selection and sizing
Suits are sized to fit the full range of crew body sizes carried onboard, and SOLAS requires that a suit be donned, unassisted, within two minutes including time to don over normal clothing and a lifejacket where worn together. Selection therefore has to check donning time for the smallest and largest crew members expected to use each stowed suit, not just an average fit. Sizing also has to account for whether the suit is worn with or without a lifejacket underneath, since some designs integrate buoyancy and others rely on a separate lifejacket.
Regulations and class
SOLAS Ch. III requires immersion suits or thermal protective aids for every person on certain ship types and areas of operation, with the insulated immersion suit standard set out in the LSA Code. Suits must carry wheelmark or equivalent type approval, a stated shelf or service life from the manufacturer, and are subject to periodic servicing intervals — commonly annual inspection with a more thorough service at intervals set by the manufacturer, often around ten years, after which replacement rather than further servicing is usually required. Stowage location and marking are checked at every safety equipment survey.
| Requirement | Detail |
|---|---|
| Core temperature test | Max 2 deg C drop after 6 hours at 5 deg C water |
| Donning time | Unassisted, within 2 minutes |
| Approval | Wheelmark/type approval under the LSA Code |
| Service interval | Annual inspection, manufacturer-set overhaul or replacement cycle |
Typical faults
- Zip corrosion or seizure — a zip that will not close fully defeats the whole suit's watertight integrity, and is the single most common defect found at inspection.
- Seam or fabric degradation — UV exposure and age embrittle the material over years of stowage, leading to leaks that only show up under a proper pressure or immersion check.
- Face seal perishing — a hardened or torn face seal lets water in around the head, undermining thermal protection even if the rest of the suit is sound.
- Incorrect stowage size mix — a locker holding only mid-size suits leaves the smallest or largest crew unable to don a suit within the required time.
What to look for in a supplier
- Current wheelmark or flag-recognised type approval certificate for the insulated immersion suit standard specifically, not the lighter uninsulated type.
- A stated manufacturer service life and clear servicing instructions, since replacement timing is set by the manufacturer, not a fixed SOLAS number.
- A size range that genuinely covers the crew list, including any known outliers in height or build.
- Servicing agent availability at the ship's normal ports of call, since suits requiring workshop service cannot always travel with the vessel.
Check the zip and face seal on every suit at every drill, not just the sealed bag date: a suit that looks fine in its stowage bag can still have a seized zip that only fails when someone tries to get into it in a hurry.
