Dangling off a hundred-storey skyscraper doesn’t sound like the safest job in the world, but it’s what these window cleaners do for a living. In fact, hanging off glass windows of some of the tallest buildings is what they do all day.

The Smithsonian Channel posted the video above on its YouTube page, showcasing perhaps the most daring job in all of Chicago, which is “window-cleaning one of Chicago’s tallest buildings”. The John Hancock Centre in particular is designed in such a manner that the windows can only be cleaned from the outside by scrubbing them down by hand. Which also means these two window cleaners in the clip have to start from the very top and make their way downwards.

Interestingly, despite the actual challenge of hanging in thin air, these workers encounter an array of other unique obstacles while on the job. Birds of prey, especially falcons, are known to nest in the facades of buildings, and can be quite aggressive if disturbed.

The phrase “occupational hazards” clearly takes on a whole new dimension here.