A cold water immersion (CWI) protocol is only as good as its endpoints. El Dorado County, California's EMS protocol 502, Heat Illness, effective June 2026, addresses a question many agencies leave vague: exactly when should crews stop cooling. The answer, written into the protocol, is a core temperature of 102°F (39°C) or below, and it allows CWI already in progress by on-scene staff to run its full 10 to 15 minutes rather than being cut short for transport, unless trauma or another complication requires immediate hospital intervention.

Why a numeric endpoint matters

Without a defined stopping point, crews face two competing risks: ending immersion too early and leaving the patient under-cooled, or continuing past the point of benefit and risking overcooling and shivering, which can itself raise metabolic heat production. El Dorado County's protocol resolves that ambiguity in advance, which matters most in the highest-stress moments of an EHS call, when crews shouldn't be making a judgment call on temperature thresholds in real time.

A wildfire-adjacent county with double heat exposure

El Dorado County sits in California's Sierra foothills, an area with significant wildland-urban interface and active wildfire seasons. That gives the county's EMS agency two overlapping heat populations to manage: exertional heat stroke from recreational and occupational activity, and heat stress in wildland firefighters working active fire lines in full PPE. A protocol with a precise, evidence-based endpoint serves both populations without needing separate guidance for each.

The evidence behind the number

The 102°F/39°C discontinuation threshold aligns with the broader literature: Casa DJ et al. (Exercise and Sport Sciences Reviews, 2007) established the CWI cooling-rate data (approximately 0.35°C/min) that makes a 10-15 minute completion window realistic, and the ACSM 2023 Expert Consensus Statement frames sub-104°F recovery within 30 minutes of collapse as the outcome target that drives survival. Documenting the exact number a protocol should target, rather than leaving "cool until better" to interpretation, is what turns consensus guidance into something a crew can execute consistently under pressure.

Where Kollder fits

Executing a precise 10-15 minute immersion window depends on equipment that reaches and holds effective water temperature fast, and that lets crews monitor the patient continuously to confirm when the discontinuation threshold is reached. Kollder One™ deploys in under 2 minutes by a single operator and provides full 360° access to the patient throughout immersion, including airway and temperature monitoring, so crews executing a protocol like El Dorado County's can track progress against the numeric endpoint without lifting the patient out of the water to check. Specifications and quotes at kollder.com/#contact.

Pour aller plus loin / Further Reading

Sources: El Dorado County EMS Agency, Protocol 502, Heat Illness, effective June 2026; Casa DJ et al., Exercise and Sport Sciences Reviews, 2007; ACSM Expert Consensus Statement 2023.

Kollder is the emergency cooling tub that deploys in under 2 minutes, anywhere.

Request a quote