The market for field-deployable cold water immersion devices remains narrow. Three manufacturers currently define the category: Corben (France), Nereus Medical with the I-CWIK (United Kingdom), and Kollder (France). For institutional buyers — fire and rescue services, military medical units, sporting event medical directors — understanding the technical and operational differences between these solutions is essential before any procurement decision.
Corben: the French incumbent
Corben is a French company active in prehospital equipment since 2004. Their emergency cooling tub is one of the earliest commercial solutions in this segment and has an established presence in French public procurement, including SDIS framework contracts notified in 2025.
Technically, the Corben tub uses an aluminium tubular frame and a welded blue PVC liner with integrated headrest. Deployed dimensions: 205 x 65 cm. A drain valve is positioned at the foot end.
Identified limitations: Field user feedback has raised concerns about the stability of the device under real-world conditions, particularly on uneven surfaces. Some practitioners have also reported questions around structural robustness with repeated use. The aluminium frame, while lightweight, offers lower rigidity characteristics than a stainless steel structure under intensive mechanical stress.
Nereus Medical I-CWIK: the British bag format
The I-CWIK (Ice-Cold Water Immersion Kit) is developed by Nereus Medical, a UK manufacturer. It is a bag-type device — the patient is immersed inside a flexible high-grade Belgian PVC envelope, sealed with fully waterproof YKK AQUASEAL zips. The I-CWIK is registered as a Class 1 Medical Device (GMDN 35474).
The bag format offers compactness and portability advantages. It is used in military, ultra-endurance, and industrial emergency contexts across several English-speaking markets, and distributed in France by MedHybride/Harvor.
Identified limitations: The closed-bag concept mechanically restricts patient access during immersion. Airway monitoring, vital sign assessment, and direct medical intervention are constrained by the enveloping structure. In prehospital emergency medicine, full patient access is not optional — it is a safety requirement. The I-CWIK addresses this through reinforced side panels, but opening the device remains slower than with an open-frame structure. The bag format is also inherently less stable than a rigid frame on uneven terrain.
Kollder: open-frame stainless steel, French manufacturer
Kollder is a French manufacturer. The Kollder cooling tub uses a different architecture from the two solutions above: open-frame food-grade stainless steel structure, deployable in under 2 minutes by a single operator, without tools.
Deployed dimensions: 205 x 80 x 60 cm. Packed and transport format: 85 x 10 x 10 cm in the included carry bag. Patient access is complete throughout immersion — airways, monitoring, and direct medical intervention are accessible at all times.
The choice of food-grade stainless steel is decisive on two levels: structural rigidity, which guarantees device stability even on uneven terrain and under the weight of an adult patient, and long-term durability against repeated use cycles and decontamination protocols. These are the precise criteria on which Kollder differentiates from the aluminium or flexible PVC solutions available on the market.
The design addresses the two most critical operational constraints identified in field use: single-operator deployment speed, and continuous patient access during cooling. The reference protocol — Cool First, Transport Second (ACSM 2023, IOC/BJSM 2021) — requires immediate immersion and continuous monitoring. An open structure is the only architecture that enables both without compromise.
Fire and rescue units, military medical teams, and sporting event medical directors wishing to evaluate the solution: kollder.com/#contact.
Decision criteria for institutional buyers
Four parameters drive procurement decisions in this segment:
Patient access. An open structure allows continuous airway monitoring, vital sign assessment, and immediate intervention if the patient's condition deteriorates. A closed bag requires reopening to intervene.
Stability and robustness. A stainless steel frame guarantees device stability on any terrain and withstands repeated mechanical stress. This is a non-negotiable criterion in emergency intervention.
Single-operator deployment. In an EHS intervention, every second matters. A device requiring multiple operators for setup diverts human resources from medical care to logistics.
Packed size. A response vehicle is a constrained space. An 85 x 10 x 10 cm packed format integrates without sacrificing cargo capacity.
Further reading
- Cold water immersion vs other cooling methods: comparison
- Exertional heat stroke: organ consequences
- Request a Kollder quote
Sources: ACSM Expert Consensus Statement 2023 — IOC, Hosokawa Y, Racinais S et al., BJSM 2021 — Casa DJ et al., Exercise and Sport Sciences Reviews 2007 — Nereus Medical, nereusmedical.com — Corben, corben.fr
Kollder is the emergency cooling tub that deploys in under 2 minutes, anywhere.
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