Negative pressure differential test

We have disignated smoking rooms in the building. Now we are planning to carry out negative pressure defferetial test for thes rooms. There are 2 questions. 1. Even if the spaces are devided by slab to slab wall, do we need to measure the difference between spaces? 2. As they are located in same place per floor, smoking rooms have other smoking rooms as their vertical adjaceny rooms. In this case we believe there is no need to have negative pressure or defference between these rooms. Are we on the right track? Thank you.