A huge colony of Pacific Walrus on Arakamchechen Island in the Northern Bering Sea. (Photo by Francois Gohier/Ardea/Caters News)

Some of London's telephone operators and engineers, trying out their gas masks at the anti-gas civilian training centre in Gloucester, where they were taught how to deal with gas attacks. (Photo by Harry Todd/Fox Photos/Getty Images). 13th February 1937

Soldiers use electronic sensors to search for missing firefighters under a line of fire trucks caught in massive gas explosions in Kaohsiung, Taiwan, Friday, August 1, 2014. A series of underground explosions about midnight Thursday and early Friday ripped through Taiwan's second-largest city, killing scores of people, Taiwan's National Fire Agency said Friday. (Photo by Wally Santana/AP Photo)

A pistol is lies near the body of a drug suspect who was killed with two others in an alleged “buy-bust” operation before dawn on Friday, September 30, 2016, in Caloocan city, north of Manila, Philippines, in the continuing “War on Drugs” campaign of President Rodrigo Duterte. Duterte said he would be “happy to slaughter” 3 million addicts. (Photo by Bullit Marquez/AP Photo)

Women carry gas cylinders to fill them at a distribution point in Cairo January 19, 2015. Egypt is going through its worst energy crisis in decades and is seeking fresh sources of natural gas, which powers most of its homes and factories. (Photo by Mohamed Abd El Ghany/Reuters)

Three workers demonstrating the different types of gas masks used in mine rescue work. (Photo by Fox Photos/Getty Images). December 1925

Convicts showcase creations during a fashion show at female penal colony No 10 in the village of Gornoye, Primorye Territory, Russia on June 7, 2017. Prisoners of the colony sew clothes at a garment factory and every year they celebrate Day of Light Industry by presenting the clothes they made. (Photo by Yuri Smityuk/TASS)