I learned the answer to this question last week after watching Supersized Earth, a BBC documentary on global cities. The show featured the window cleaning company Cox Gomyl, whose brave workers are tasked with cleaning the Burj Khalifa tower in Dubai, the tallest building in the world.

It takes a team of 36 window cleaners three months to clean the 2,717-foot building, which has 24,000 reflective windows and about 120,000 sq metres of glass.

They are able to do this terrifyingly daunting task with with 12 state-of-the-art machines that travel along tracks fixed to the exterior of the building. Operating at heights of 2,000 feet and covering 40 storeys each, the machines will ply the superscraper's facade even in high wind, blazing sun and during dust storms, with the cleaners inside harnessed to metal cages.

According to an article in The Telegraph, the cleaners will carry electrolyte packs and wear specialised clothing resembling moon suits, while working only on parts of the building that are in shade.

As I was researching this article, I learned that sadly (or maybe not so sadly) this job may soon be rendered obsolete by Swiss robots. 

Serbet's Gekko, a window cleaning robot

Several companies have invented robots to replace window cleaners, like the Swiss company Serbot's , Gekko, a disk-shaped robot that has a cleaning capacity of up to 400 square metres an hour (which is apparently fifteen times faster than manual cleaning). It uses vacuum power to attach itself to the surface to be cleaned, then applies a windshield-wiper type of brush to blast away any kind of dirt.

In an interview with UAE newspaper, The National, Mazen Harake, the managing director of Spider Access, which cleans more than 400 high-rise buildings in the UAE by hand, said that robots will never be as effective as humans.

"We've had previous encounters with about five of these robotic cleaners, mostly Swiss-made," Harake said. "They are very expensive, require a lot of maintenance, and are not very effective. The main issue is access restriction. These robots can only go up and down and can't reach all the areas. They will not affect our business at all."

It's comforting to know that good, old fashion human sweat equity can sometimes win the battle against technological innovation. 

According to Supersized Earth narrator Dallas Campbell, who had the experience of cleaning the Burj Khalifa for the documentary:

"It strikes me when we are out here, that even though we are in such a technically advanced building, in order to keep it nice and clean you still can't beat a man with a squeegee and a bucket."

And once they have cleaned all 24,000 windows in three months, they must start all over again.

Photo: CNN