Reno:

This intriges me:
"It's also interesting that the safety department has forbidden getting to the fan using the very means used by the original contractor."

Could this 'means' be taking the big cover off from the roof to access the fan??

I had something similar back in the day. Vacant bldg, 45' slab to deck; unmarked panels; we dumped the main and did an attack from the rooftop.



John