The Space Needle cleaning crew in action:

Photo: Karcher GmbH & Co.

Employees of Karcher GmbH & Co. are doing the work. They get paid. Karcher does not:

Early on, Kärcher determined that it would donate its cleaning services of public monuments, donating skilled labor as well as the technical, analytic and supervisory services necessary to complete such projects. Their reasoning was twofold: not only was the donation a goodwill gesture, but the feedback the company’s engineers received was invaluable in refining the innovation and manufacture of future cleaning systems.
To that end, Kärcher has carried out some 80 cleaning projects on historical monuments,…

Via Kottke.