In my submarine thriller, The Custom of the Trade, I describe an accident in an early submarine caused by hydrogen gas. Even today, hydrogen gas can be a killer in submarines. It has been reported that the recent accident in the Russian nuclear submarine, Losharik, was caused by a hydrogen gas explosion.
Before the advent of nuclear propulsion, submarines were entirely reliant on battery power when dived. Today, batteries are a back-up in the event of having to shut down the reactor. The trouble with batteries is that they give off hydrogen gas. Even in the days when it was not possible to provide ventilation for the submarine crews, submariners were careful to provide fans over the battery cells to ventilate the lethal gas, as it is highly combustible and a fire in a dived submarine is bad news, indeed.
Hydrogen is not the only lethal by-product of submarine batteries, however. A bigger problem for the submarine crews of conventional submarines (ie non-nuclear powered), is that when a battery cell is exposed to seawater, it gives off chlorine gas, the same poison gas used in WW1. On the surface, it is common practice to run with a hatch open in order to feed fresh air to the diesel engines. In rough weather, it is not unusual for the interior of the submarine to be swamped by large waves and when the seawater drains through the deck below, it finds the battery cells.
The Losharik tragedy this year and the loss of the Argentinian submarine ARA San Juan 18 months ago, are reminders of the dangers submariners of all nations have always faced and continue to fear.