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  • AutorenbildMichael Mutter

A case of skin burns during a cold water dive

Year-round diving in Swiss lakes is becoming increasingly popular because of the good visibility. To overcome the stakes of hypothermia, divers like to use active heating measures in addition to passive insulation. In recent years, the industry has developed battery-powered heating garments that can be worn in dry suits.

We report the case of a diver who suffered 2nd degree burns due to an overcurrent in the heating suit during a dive.

Click here for ice diving in the Klöntalersee with the diving school H2O.

Ice diving in the Klöntal. Picture: Tauchschule H2O

Case history

In December 2022, a fit 35-year-old diving instructor undertook a night dive in a group of three divers from a boat in a Swiss lake on open circuit (D12) using nitrox (EAN 32) to a maximum depth of 27 msw. Due to the environmental conditions (air temperature 2° C, water temperature 4° C), he used an electrically heated system that he wore under his drysuit consisting of a whole-body suit and two gloves (+ 200 dives and + 50 dives performed respectively), which were directly coupled to the sleeves of the suit. Power was provided by an external battery pack worn on the harness (Li-ion 11.1 V/3 cells à 3.7 V, 24.5 Ah). After 30 minutes of the dive, he switched on the active heating system. Within seconds, he felt a sharp, burning pain in both shoulders. This prompted him to immediately switch off the heating system and additionally disconnect the cable from the external battery. Because the pain persisted, the dive was aborted. The group immediately ascended to the surface within the no decompression limit and returned to port. After removing the gear, 2nd degree skin burns with blistering were found over both his shoulders and on his upper arms (figure 1 and 2). The fabric of the heated underwear had partially melted in the area of the shoulders and over the upper arms.

Skin burns. Published with patient´s consent

Skin burns. Published with patient´s consent

Forensic examination

The entire heating system, including the battery, was examined by computed tomography and tested both physically and electrically by the Forensic Institute of the Zurich Cantonal Police Force. The lithium battery used worked properly and the amperage and voltage it supplied did not exceed the needs and specifications of the heating suit. The thermostat was identified in the suit and its functionality was proven. However, no fuse against an electrical overcurrent was installed in the suit. The insulation of the electrical line to the right-hand heating glove, which was built in the suit, had melted from the neck to the sleeve cuff. A cable break was found on the right-hand heating glove immediately after the plug socket, which connected it to the in-suit electrical supply line.

This cable break created an alteration in contact resistance, which heated up and melted the insulation of the glove’s electrical supply line in the suit. The high electrical current and the resulting temperatures also bent the contact of the thermostat. However, this had no influence on the melting of the insulation, since the thermostat only switched due to the temperatures and not due to an electrical overcurrent.

The clinical course of the burn injury was uneventful. The blisters healed completely with conservative therapy.


Heat loss is an important issue in diving, not only but specifically in cold water. Hypothermia leads to confusion, disorientation, switch-off phenomena, cardiac arrhythmias and eventually unconsciousness and death if the core temperature drops below 35°C. In addition, body temperature has a direct effect on tissue saturation and desaturation of inert gases and thus on decompression. A low body temperature causes a centralization of blood flow. As a result, there is delayed inert gas saturation of peripheral tissues, which is a desirable effect. However, this also leads to slower desaturation, which has an unfavorable effect on decompression. Indeed, one study showed a significant decrease in the incidence of decompression sickness (DCS) in a group of divers who were warmed up during decompression compared to a group that was not warmed up during the decompression phase. Thus, it is recommended as best practice to actively heat the diver only as much as necessary to avoid incapacitating hypothermia during the bottom time, and to use an active heating system warmer only during the decompression phase. From this point of view, switching on the heating only when feeling cold or during ascent, as it was done in our case report, was correct, even though study data were not collected on scuba divers.

The dive team performed a predive-check, however without turning on the heating, thus potentially missing a possible malfunction before the dive. This underscores the need to check all diving equipment for proper function before a dive.

The use of heating systems that are not specifically approved for diving is strongly discouraged.

Passive thermal insulation is often not enough to protect divers in cold waters.

In addition to passive protection against heat loss, scuba divers like to use other heating measures, such as chemical heating packs and heated underwear, which are used in winter sports. These gadgets are not specifically approved for diving and accidents are known, both published and anecdotal. For instance, an air-activated heating pack auto-ignited due to a high partial pressure of oxygen causing severe burns to the diver. For this reason, the use of heaters not approved for diving is strongly discouraged. This explicitly also applies to carrying batteries in a dry suit, as a possible battery fire would be harmful.

Batteries should never be carried within a dry suit.

In recent years, the diving industry has developed battery-powered heating systems - from small vests to full-body suits - that are approved for dry and wet suits. Although these devices are approved for hyperbaric conditions and carry appropriate CE marks, they are not immune to malfunction. In our case, the breakage of a cable in the heating glove caused an overcurrent in the power supply line within the heating suit, resulting in second-degree burns. The protection against an overcurrent in this case was not an electrical fuse, but a thermostat that did not break the circuit until the temperature reached 70°C. In contrast, the suit's user manual specifies a maximum heating temperature of 45° C. A fuse that would protect against overheating and overcurrent was missing.

Manufacturers of heating systems for diving are urged to tailor their products to the needs of divers without compromise.

The heating system is manufactured by a renowned diving equipment company whose products are highly appreciated in the diving scene, carry a CE mark and are marketed specifically for diving. However, the electrical configuration of the heating suit does not meet the promised safety requirements. Fortunately, the dive could be terminated immediately within the no-decompression limit. The malfunction of the heating suit could have led to further consequences such as barotrauma or decompression sickness if a proper ascent or decompression obligation had been omitted due to panic.

In response to this diving accident, the manufacturer has agreed to revise the electrical configuration of the heating suit to eliminate future malfunctions.

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