Immersion suits, anti-exposure suits and thermal protective aids
1The lesson in plain words
A lifejacket provides flotation. An immersion suit adds thermal protection; a thermal protective aid reduces heat loss inside a survival craft.
Immersion suits
An immersion suit is a waterproof suit covering the whole body except the face; gloves may be separate but are permanently attached. On cargo ships SOLAS requires one for every person on board, plus suits at watch or work stations far from where the suits are stowed. Only ships other than bulk carriers that always trade in warm climates may be exempted by their flag state. You must be able to unpack and don it without help within 2 minutes, including any lifejacket worn with it.
What it must do
In approval tests, the suit allows you to climb a 5 m vertical ladder, swim a short distance and board a survival craft. It must withstand a 4.5 m test jump. You must be able to turn yourself face-up within 5 seconds. This is not automatic self-righting. If the suit needs a lifejacket, wear it over the suit. A suit approved for use without a lifejacket has its own light and whistle.
Insulated or not
In approval tests, an insulated suit limits your core temperature fall to 2 °C after 6 hours in water at 0–2 °C. An uninsulated suit limits the fall to 2 °C after 1 hour at 5 °C, worn over warm clothing. These are controlled test results, not guaranteed survival times. Wear the clothing specified for your suit.
Anti-exposure suits
An anti-exposure suit is a working suit for rescue boat crews and marine evacuation system parties. It gives at least 70 N of buoyancy, is donned within 2 minutes, has a hood, gloves and a pocket for a portable VHF (very high frequency) radio, and lets you work and handle a boat. In approval tests in water at 5 °C, core temperature must fall no faster than 1.5 °C per hour after the first half hour. This is a test limit, not a survival-time guarantee.
Thermal protective aids
A thermal protective aid (TPA) is a bag or suit of waterproof material that holds heat in, carried in lifeboats and liferafts. It covers the whole body of a person wearing a lifejacket, except the face, and cuts heat loss from wind and evaporation. Put a cold or wet survivor in one once inside the craft. It works in air from −30 °C to +20 °C; if it hinders swimming, you can take it off in the water within 2 minutes.
2Key data
- Immersion suit donning
- Within 2 min, unaided, with any lifejacket needed
- Insulated suit
- Core fall of 2 °C or less after 6 h in water at 0–2 °C
- Uninsulated suit
- Core fall of 2 °C or less after 1 h at 5 °C, over warm clothes
- Anti-exposure suit
- 70 N or more; core fall ≤ 1.5 °C/h at 5 °C after 0.5 h
- TPAs in survival craft
- For 10 % of the persons or two, whichever is greater
- TPA air range
- −30 °C to +20 °C
3Key points
- 1
Cargo ships carry an immersion suit for every person; only some non-bulk carriers in warm climates are exempted.
- 2
Don it unaided within 2 minutes; a lifejacket, if needed, goes over the suit.
- 3
Insulated: 2 °C core fall in 6 h at 0–2 °C. Uninsulated: 1 h at 5 °C, over warm clothes.
- 4
Anti-exposure suits are working suits for rescue boat crews.
- 5
TPAs in survival craft cut heat loss from wind and evaporation.
4Frequent mistakes
Wrong: An uninsulated immersion suit is warm enough over underwear.
Right: An uninsulated suit must be worn over the specified warm clothing to provide its tested thermal protection.
Wrong: Put the lifejacket on first and the immersion suit over it.
Right: If the suit needs a lifejacket, the lifejacket goes over the suit, never underneath.
Wrong: A thermal protective aid is a swimming suit for the water.
Right: A TPA is used inside the survival craft. Take it off in the water if it stops you swimming.
5Practice case & exam keys
Your bulk carrier is in the North Atlantic in winter. At the drill, a new crew member says he will not bother with the immersion suit, because his lifejacket will keep him afloat.
Show the answer
A lifejacket keeps him afloat, but in near-freezing water cold soon weakens him and can kill. Bulk carriers must carry an immersion suit for every person, and he must be able to don it within 2 minutes. Help him practise at the drill: warm clothes underneath, suit on, then the lifejacket over it if the suit is marked for one. Show him the light, whistle and buddy line.
Exam keys
- Immersion suit for every person on cargo ships; bulk carriers have no warm-climate exemption.
- Donned unaided within 2 min; 4.5 m approval jump test; turn yourself face-up within 5 s, not automatic self-righting.
- Insulated: ≤ 2 °C core fall after 6 h at 0–2 °C; uninsulated: after 1 h at 5 °C.
- TPA: covers all but the face, works −30 °C to +20 °C, removable in water within 2 min.
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