Nuclear submarines, when at sea, usually operate submerged in a closed and hermetic environment. To avoid the dangerous accumulation of carbon dioxide (CO2), they use a special purification system. This system is based on the use of a chemical substance called amine, which has the peculiar ability to absorb CO2 at lower temperatures and release it when the temperature rises. The amine is processed by a piece of equipment known as a CO2 scrubber, which alternates between heating and cooling the gas, directing it to the ocean and keeping the internal air safe to breathe. Although this system is extremely effective, it has a “side effect”: the amine gives the air a very distinct odor, which ends up impregnating every corner of the submarine, from the internal compartments to the clothing and skin of the crew. In addition to this smell, sailors are also exposed to aromas coming from the kitchen, hydraulic oil vapors, diesel engine exhaust gases, ventilation of sanitary tanks and the collective smell of many people confined in a small space. Over time, crew members get used to these odors, but outsiders always notice them.

Once, upon returning from a mission in a submarine, I flew home dressed as a civilian. During the flight, an elderly lady asked me, “Have you been on a submarine?” Surprised, I answered yes, and she told me that her husband had served on a submarine and that she would never forget the distinctive smell of those ships.