There are some limited exemptions for workplaces where people also reside, such as care homes. In these workplaces, smoking is allowed in either a bedroom or a designated smoking room, but only by residents and their guests. Employees are not allowed to smoke on the premises, except in smoking rooms on offshore platforms. Hotels and guest houses may allow smoking in designated bedrooms. To gain these exemptions, the rooms have to be designated in writing by the person in charge of the premises as rooms where smoking is permitted. The rooms must not have a ventilation system which vents into other parts of the premises.