I am new to NFPA and I am trying to determine spray density. I have yet to hear a definition for basing a "area of sprinkler operation" - NFPA 13 - Figure 11.2.3.1.1. I am trying to size for a 37,000 ft^2 building and all I hear from people are "rules of thumb". I fall in Ordinary hazard 2 and I...