There is a very good presentation by Simo Hostikka from Aalto University at the 2016 Fire and Evacuation Modelling Technical Conference put up by Thunderhead Engineering on Youtube - https://www.youtube.com/watch?v=4bH3Ast47nw&t=6s .
The presentation discusses modern airtight (relatively) apartments and fire pressures being such that apartment doors cannot be opened for escape.
Worth looking at.
Robert Peart
C/VM2 is a verification method; not a design code