Skyscraper cleaners working on high buildings are often visible to people on the ground. Photo provided to China Daily

Even though he has cleaned skyscrapers for about 20 years, Hu Bensheng, 39, still feels nervous every time he scales the heights.

The job is much more difficult than people might imagine, says the real-life spiderman who works for Shanghai Xin Dong Hu Environmental Clean Technology Co Ltd.

"In good conditions it usually takes us 20 working days to complete a 240-meter-tall building. But with the time off for wind or rain added, that can stretch to a month."

One of the keys to the safety of Hu and his colleagues is their ropes—apart from the main ropes, there are safety ropes—which are made of polyamide and are at least 2 centimeters in diameter.

"I have been in this industry for 20 years and have not seen an accident in our company. We attach great importance to safety. Both the work ropes and safety ropes have to be changed every two years under government regulations, but our company changes them more frequently to be on the safe side."

Hu says if a project has extreme safety risks, the company will turn it down.

"The managers will not put our lives at risk," he says.

On a regular day, Hu works six to seven hours, with a 90-minute lunch break.

Unlike many other migrant workers in first-tier Chinese cities, Hu has lived with his wife and son in Shanghai since he arrived from his hometown, Lu'an, in Anhui province, 20 years ago. His son, 14, has now returned there to attend junior high school.