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)

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

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)

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)

“Very small forest-dwelling wallabies are known as pademelons (genus Thylogale) and dorcopsises (genera Dorcopsis and Dorcopsulus). The name wallaby comes from the Eora Aboriginal tribe who were the original inhabitants of the Sydney area. Wallabies are herbivores whose diet consists of a wide range of grasses, vegetables, leaves, and other types of foliage”. – Wikipedia

Photo: A baby wallaby sits in a zoo attendant's lap at Edogawa Natural Zoo on August 4, 2009 in Tokyo, Japan. The staff of the zoo have raised the young wallaby after her mother neglected her. (Photo by Junko Kimura/Getty Images)

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)