Protesters run for cover after riot police fired tear gas towards the bridge they were climbing down to the road below, to escape from Hong Kong Polytechnic University campus and from police, in Hung Hom district in Hong Kong on November 18, 2019. Dozens of Hong Kong protesters escaped a besieged university campus on November 18 by lowering themselves on a rope from a footbridge to a highway, AFP video showed. Once on the road they were seen being picked up by waiting motorcyclists. (Photo by Anthony Wallace/AFP Photo)

Drivers push cars to gas station during “oil crisis”, Roslindale, Boston, Massachusetts, 1973. (Photo by Spencer Grant/Getty Images)

A coil-shaped Helix Nebula showing a fine web of filamentary “bicycle-spoke” features embedded in the colorful red and blue ring of gas. At 650 light-years away, the Helix is one of the nearest planetary nebulae to Earth. A planetary nebula is the glowing gas around a dying, Sun-like star. (Photo by Reuters/NASA)

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)

Riot police fire tear gas at demonstrators during a protest against fare hikes for city buses in Sao Paulo, Brazil, January 8, 2016. Brazilian riot police on Friday fired tear gas and stun grenades to disperse a violent protest against a rise in public transport fares in the country's largest city, Sao Paulo. (Photo by Nacho Doce/Reuters)

People assist a woman who was exposed to tear gas by pouring milk over her face after police fired tear gas and water canon to try and disperse protesters outside Parliament on November 17, 2020 in Bangkok, Thailand. The demonstrators gathered outside parliament, on Tuesday, as the Thai government met to discuss amendments to the country's constitution. (Photo by Lauren DeCicca/Getty Images)

A man wears a gas mask as he holds a bouquet of flowers, following the outbreak of the novel coronavirus on Valentine’s Day in Hong Kong, China on February 14, 2020. (Photo by Tyrone Siu/Reuters)