It is not allowed to smoke in the dormitories common areas. That also include staircases, galleries, basements, the laundry rooms, common rooms, etc. Smoking is therefore only allowed in the private accommodation, where it is allowed according to the house rules, or outside. This is substantiated in the law of smoking.
The law of smoking became effective the 15th of August 2007 and it consists of a general non-smoking rule in the public as well as the private job market. The law is therefore primarily a work environment law. It contains rules about public areas such as public transport and serving places. The purpose of the law is to make more non-smoking environments to prevent health risks for passive smoking and to prevent that someone is involuntary exposed to passive smoking.
In all dormitory resident meetings in 2018, the residents decided that all dormitories should be non-smoking areas, including the accommodations themselves. Therefore, tenants who move in after September 2018 are not allowed to smoke in their accommodations either, as stated in the lease.
Note that the residents are responsible for their guests behavior.