The wording is from the floor to 6 feet above the equipment or up to some type of structural ceiling.
We had a similar situation with tons of foreign piping above the gear in a job in downstate Illinois and they installed a concrete slab below the gear and the piping. The AHJ said that a suspended ceiling or drywall wasn't acceptable, but he would accept something "that you could walk on".
BTW, be glad that you're not in Chicago, where the space isn't just above the equipment, but also above the working space.
