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

Dancers at the Windmill Theatre in London, England practice a routine wearing gas masks and hard-hats with their costumes, 1940. (Photo by Hulton Archive/Getty Images)

“Man is least himself when he talks in his own person. Give him a mask, and he will tell you the truth”. – Oscar Wilde. (Photo by Lala Roe)

Prayer flags fly at Namgyal Tsemo Monastery above the town of Leh in Ladakh, India September 24, 2016. High in the Indian Himalayas, young novice monks in maroon robes take their lessons inside the 15th-century Thiksey monastery. (Photo by Cathal McNaughton/Reuters)

Mananya Boonmee, 49, works on the make-up of a “child angel” doll at her house in Nonthaburi, Thailand, January 26, 2016. A craze for lifelike dolls thought to bring good luck is sweeping Thailand, reflecting widespread anxiety as the economy struggles and political uncertainty persists nearly two years after a coup. (Photo by Athit Perawongmetha/Reuters)

A woman works in a rubber plantation in Yala province, southern Thailand, January 30, 2017. Thai rubber exporters say they have enough of the commodity in stockpiles to ensure only minimal disruption to scheduled shipments in the wake of deadly floods in key growing regions. (Photo by Surapan Boonthanom/Reuters)

In this October 6, 1976 file photo a member of a Thai political faction strikes at the lifeless body of a hanged student outside Thammasat University in Bangkok October 6, 1976. For some Thais, the bloody events of October 6, 1976 are still a nightmare. On that day, heavily armed security forces shot up Bangkok's Thammasat University campus and killed scores of students, while right-wing vigilantes captured would-be escapees, subjecting them to ghoulish lynchings. (Photo by Neal Ulevich/AP Photo)