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)

Masks of Republican presidential candidate Donald Trump (C) and Joaquin "El Chapo" Guzman (2nd L) are seen at Grupo Rev in the Mexican city of Cuernavaca near Mexico City, October 14, 2015. (Photo by Henry Romero/Reuters)

A women wearing a mask to protect from extreme smog visits the Tiananmen Gate in Beijing December 8, 2015 as China's capital issues its first ever "red alert" for pollution. (Photo by Damir Sagolj/Reuters)

In this Monday, March 10, 2014 photo, a 9,000 year-old mask is on display at the Israel Museum in Jerusalem. The exhibition called “Face To Face” shows eleven stone masks, said to have been discovered in the Judean desert and hills near Jerusalem, which date back 9,000 years and offer a rare glimpse at some of civilization's first communal rituals. (Photo by Tsafrir Abayov/AP Photo)

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

Members of Japanese idol group Kamen Joshi (Masked Girls) pose for a photo after a rehearsal for a concert at their theatre in Tokyo's Akihabara district, Japan March 17, 2016. For countless girl and pop-idol bands in Japan, standing out from the crowd can be daunting, but one group – “Kamen Joshi” – seems to have found the answer by hiding behind masks. The Tokyo-based all female band has 18 members, split into three groups that perform across Japan and elsewhere in Asia. (Photo by Toru Hanai/Reuters)

A man dressed as a devil poses next to a grafitti of late rebel hero Ernesto "Che" Guevara in the indigenous community of Monimbo in Masaya, Nicaragua, October 16, 2015. People prepare to participate in the popular annual festival called "The Aguizotes" held on the last Friday of October, where residents dress up as characters from legends and folklore mythology of Nicaragua. (Photo by Oswaldo Rivas/Reuters)