While it is always better to treat bed bugs before a tenant moves sometimes there is no other choice, usually because of the tenant failing to cooperate, but to have a tenant move out of a building with infested furniture. One thing the exterminator can do in this setting is to ensure that the suite (baseboards, door and window frames, etc) is always well treated. Over a period of time the bugs will abandon all the areas that have been treated and infest areas that have not been treated. Therefore all untreated items such as clutter, boxes, papers, books etc., will become infested. When the tenant moves out the bugs will all be in the untreated belongings.
Then the exterminator needs to time the hallway chemical treatments to coincide exactly with the move out day. Preferably the hallways should be treated just before and just after the move.
I have recently followed this procedure with a tenant nursing a small bed bug infestation over 6 months due to non cooperation. The suite was constantly treated over that 6 month span and the hallways treated before and after moving.
Then we removed and discarded the baseboards and treated the those areas chemically. No activity was noted. A bed was set up closest to the known infested area and climb up interceptor/ glue board traps were set up. A person has been sleeping on this bed every night for three weeks and there has been zero activity. Once we reach 6 weeks of zero activity I will declare the suite clean. I will allow a new tenant to move in at the 4 week mark with instructions to maintain the traps for another 2 weeks.
It appears the low level infestation has exported out of the building – excellent!