You only need to add emissions to your process when it is a direct emitter itself. E.g. when modeling the use phase of cooling systems (aircons, fridges etc), usually a small amount of coolant leaks slowly from the pipes during the many years of operation. Or if you use household biomass boilers to produce heat, it lets out particulates, NOx, VOC, SOx, soot etc
Obviously you have to know these processes well enough to be able to measure or estimate these emissions. This is usually only necessary when the process has a central role in your product system. Otherwise you should rely on the processes in your database and don't touch the emission flows until you know what you do.
Hope it helps,