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

South African maidens wrap themselves in blankets as they head to a ritual bath in a local river on September 5, 2014 at the eNyokeni Royal Palace in Nongoma in the KwaZulu-Natal region ahead of the 13th anniversary of the Reed Dance (uMkhosi woMhlanga) celebrated by the Zulu King Goodwill Zwelithin. As part of the ceremony, the young women dance bare-breasted for the king, each carrying a long reed, deposited later as they approach the King and is a cultural celebration that promotes respect for young women, and preserves the custom of keeping girls as virgins until marriage. (Photo by Marco Longari/AFP Photo)

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 competitor makes their way through fire as they take part in the Tough Guy endurance event near Wolverhampton, central England, on January 27, 2019. The Tough Guy event challenges hundreds of competitors to run a gruelling course whilst negotiating up to 300 obstacles including water, fire, and tunnels. (Photo by Oli Scarff/AFP Photo)

A competitor reacts as she emerges from the water during the Tough Guy event in Perton, central England, January 26, 2014. The annual Tough Guy race – “the toughest race in the world” – at Perton in Staffordshire. Tough Guy claims to be the world’s most demanding one-day survival ordeal. First staged in 1987, the Tough Guy Challenge has been widely described as one of the hardest races of it’s type with up to one-third of the starters failing to finish in a typical year. (Photo by Darren Staples/Reuters)

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)

A fireman from the London Fire Brigade, wearing a smoke helmet. (Photo by Topical Press Agency/Getty Images). Circa 1908