We understand that Strategy 4 requires that each ventilation system that supplies recirculated air to occupied spaces have particle filters or air-cleaning devices. Our design proposes MERV 14 filters for all ventilation systems supplying air within the building, with the exception of vestibules that are only equipped with air curtains above each door to prevent cold air from coming in during winter. Since the mechanical engineer does not consider vestibules intended for human activities, and as such, are not occupied spaces as per the definition, we consider to be compliant with the strategies requirement. Could you please confirm whether or not our interpretation is correct ?