the owners want to evaluate how in compliance to 101 the mall is 'as is'.
Maybe.
To evaluate if it currently meets 2009 NFPA 101, you need to review Ch. 37 Existing Mercantile Occupancies. Yes, 37.3.1 allows any vertical opening protection allowed in 8.6, and 8.6 permits no separations and no smoke control for "
existing, previously approved atriums"; but don't forget the special provisions specifically for Malls in 37.4.4. If the egress travel distance exceeds the max for any of the occupancies served by the mall common area, it is allowed to be increased an additional 200 ft if (among other things) "
Malls with a floor opening connecting more than two levels shall be provided with a smoke control system.". So it is possible that this "open to above" area may need smoke control, not because it is an atrium, but because max travel distance is otherwise exceeded.
Existing ones are already approved.
Well, yeah, I suppose. I agree that if the original building "got away without" smoke control, none is needed now. IMHO, "existing, previously approved atriums" is a pretty weak statement, and fairly unique to the codes. In most other code topics, it always goes back to "code in effect at the time". Usually, if the code officials missed something required by the code in effect under the original permit, it is "oops my bad, but you have to retrofit" the next time around. Here, if Radar O'Rielly slipped a CO into a pile of paper, and CBO Blake signed it, the atrium will never be required to have smoke control.