Ice on the regulator caused free flow, resulting in an aborted dive.
Reported Story
The day of the dive was relatively cold. The water temperature was 35°F (1.6°C), and the air temperature was 38°F (3.3°C). There was no ice on the water near our dive area. After five minutes into the dive at about 22 feet (6.7 m), my regulator started to buzz on inhale. After three noisy inhalations, the second stage began to free flow, and the BCD inflator was stuck open.
I yelled through my regulator, attempting to signal my buddy, and I flared out my legs to slow my ascent. I switched to my alternate second stage while trying to release air from the BCD. My buddy and I surfaced together, and my buddy was able to turn off the tank valve. The first stage of the regulator was completely covered with ice. We decided to terminate any diving for the rest of that day.
Comment
Diving in cold water even in the absence of ice cover can create serious problems with equipment. The expansion of high-pressure air from the cylinder to intermediate pressure in the first stage produces a cooling effect. Despite the fact that the water temperature is above freezing, the cooling can cause the temperature of the first stage to reach 32°F (0°C) or lower. Ice can and will form on the first stage, interfering with proper function.
Most modern regulators in this situation will free flow rather than stop providing breathing gas. As this diver discovered, the same cooling with expansion effect can cause the inflator/deflator mechanism on the BCD to malfunction as it ices as well. It is paramount when diving in cold water to make sure that your regulator and other equipment are compatible with the cold environment to avoid potentially dangerous situations. Work with the professionals at your local dive shop to select and/or prepare equipment for this harsh environment.
Marty McCafferty, EMT-P, DMT, EMD-A