Gas detection is very important in the maritime transport industry, due to closed watertight environments such
as machine rooms and various freight storages and gas tanks. These applications go for long periods of time
without ventilation and are likely to contain potentially toxic or explosive gases.

Effective oxygen detection is critical in confined spaces. The lack of oxygen aboard a ship normally occurs
due to oxygen enrichment (rust), organic oxygen consumption (grain transport) or the displacement of gas
by other gases (inert gases aboard oil tankers).

Explosive and toxic gases come from the metabolism of mold – CO2 detection in ballast tanks, explosive
hydrocarbon vapors issued from the burning of fuel (machine rooms), hydrogen (battery-charging rooms),
ammonia or freon (cold rooms), H2S (wastewater) etc. Additionally, risks related to gas mixtures are always
possible, and a continuous and simultaneous gas detection system should be implemented for any
Work being carried out aboard the ship.

Hydrogen sulphide stinks of rotten eggs, but kills without smell

Hydrogen sulphide is a poisonous gas whose odor in small doses is associated with the stench of rotten eggs.
At higher concentrations, the gas paralyzes the sense of smell, which means that we rarely detect the spill
before it is too late. The typical cause of death in hydrogen sulfide accidents is respiratory arrest.

Hydrogen sulphide is a toxic gas species with the chemical formula H2S, which typically occurs in sewers, manure and septic tanks, cargo holds with trash fish and other places with oxygen-poor conditions. It is typically formed by the breakdown of sulfur-containing proteins, or by sulfate-reducing bacteria reacting inorganic sulfite or sulfate. It can also be found in crude oil, natural gas and biogas.

In 2014, two fishermen perished on their fishing boats at Strandby in North Jutland as a result of a hydrogen sulfide accident. The accident occurred when the two fishermen were in the cargo hold and were unloading trash fish. Here they were exposed to a high concentration of hydrogen sulfide, which cost them their lives. Along the way, a pump man tried to rescue the two fishermen – he is brain damaged today.

Few notice the hydrogen sulphide gas in case of accidents

The concentration of hydrogen sulphide is crucial to the impact on the body. At 0.0003 to 100 ppm (parts per trillion / billion parts) we will notice the gas as it sets tracks in the air in form of a heavy stench of rotten eggs. If you exceed 100 ppm, the gas will stun the sense of smell, which means that we can no longer smell the gas, and theoretically do not know that we are in danger. At a concentration of 500 ppm and above, the gas will cause respiratory arrest, which is the typical cause of death in hydrogen sulfide accidents.

Another example of a hydrogen sulfide accident was when a pump on a paper mill broke, causing a hole in the pump housing. As a result, large amounts of a sulphide containing solution ran into the sewer where it reacted with a slightly acidic liquid and even released hydrogen sulphide. Twelve people were seriously poisoned and two died. Subsequently, it turned out that of the ten survivors, only two had detected the smell of rotten eggs.