According to the next few sentences in the article:
> The film was taken off the main roll at high speed, flowed upwards 20ft to overhead rollers, passed horizontally 20ft and then downwards to the slitting device, where it was spooled onto shorter rolls. The whole operation formed a cubical shaped tent, with two walls and a ceiling approximately 20ft square.
>> When he attempted to walk through the corridor formed by the moving film, he was stopped about half way through by an "invisible wall."
A corridor formed by the moving film?
I have a hard time understanding the situation.