I bought a fairly large (750 KV) VDG kit on eBay a couple of years ago just for the lulz, and I soon came to appreciate how unpredictable and unintuitive electrostatic phenomena can really be. Not only was the charge-transfer mechanism between the belt, rollers, and brushes completely different from what I'd always assumed, but the macro-level effects were sometimes downright confusing. In some ways, the operation of a Van de Graaff generator is even harder to internalize than that of a Tesla coil.
I expected longer discharges in dry weather -- nope, it does better in moderate humidity. I expected styrofoam peanuts to be consistently attracted (or maybe repelled) when thrown at the sphere, not to be attracted at first and then rapidly repelled at some small distance from the sphere. I expected the strongest discharges to occur when the generator was operated with no large objects nearby; instead, positioning it within a few feet of a tall wooden bookcase results in sparks (in any direction) at least 25% longer.
So I'm not too surprised at tales of strange force fields in a cellophane-tape factory. I am surprised that the rollers didn't have grounding brushes all over the place... but given my experiences with the VDG, for all I know that would have made things worse.
From what I was told in high school when they used to bring out the VDG's was that it would take a voltage potential in the millions to be harmful.
What my guess would be is that the mechanical energy from forcing the charged cellophane into compact rolls was forcing the free-electrons off of the cellophane belt and they were simply carrying on travelling. By the description it sounds like the rolling phase was giving the electrons a downward motion if it was a "tent" shape operation.
My guess it that it was simply a voltage-potential field. If the energy had found a way to ground itself it would have, and anyone walking around on a concrete floor wasn't going to provide a quicker route to ground. Probably similar to how a pigeon doesn't explode sitting on a power line, because despite sitting on a line with millions of watts of potential energy, until it comes actual energy (like when a tree branch hits across the lines) it's not dangerous.
Rather than a "force field," another possibility was Taser effect, where numerous tiny sparks to the skin will cause muscles to clench, making it impossible to walk. Search keywords: tetanizing beam
I expected longer discharges in dry weather -- nope, it does better in moderate humidity. I expected styrofoam peanuts to be consistently attracted (or maybe repelled) when thrown at the sphere, not to be attracted at first and then rapidly repelled at some small distance from the sphere. I expected the strongest discharges to occur when the generator was operated with no large objects nearby; instead, positioning it within a few feet of a tall wooden bookcase results in sparks (in any direction) at least 25% longer.
So I'm not too surprised at tales of strange force fields in a cellophane-tape factory. I am surprised that the rollers didn't have grounding brushes all over the place... but given my experiences with the VDG, for all I know that would have made things worse.