Placing VOC Sensors forAssessing Air Quality : A CFD Study of Indoor VOC Distribution

Abstract: The Swedish Obligatory Ventilation Control (OVK) was established to ensure that ventilation systemsare clean and work according to design. The control system of today is however not perfect, and thereare many aspects of OVK which could be approached differently for improved efficiency and occupanthealth. A current project in Stockholm is looking at the possibility to use sensors, continuouslymetering volatile organic compounds (VOC), temperature, and relative humidity, in place of the airflowmetering of the traditional OVK solution. One of the first issues encountered was sensor placement, asthe sensors must be discreetly installed on available surfaces while the collected air quality data mustrepresent the air in the occupied zone. A second challenge concerns how the sensor outputs should beinterpreted in terms of indoor air quality.The main purpose of this thesis is to suggest a model that can evaluate the suitability of differentplacements of sensors (such as the ceiling, walls, or lamp fixtures) from a VOC perspective. The idea isto evaluate what areas of the room best represent the average air quality of the occupied zone. This partof the study was approached by combining literature review and computational fluid dynamics (CFD)in two case studies; one office and one apartment. The intent behind the iterated method is to present ageneral CFD model that can be easily interpreted and adapted to accommodate new objects (e.g.building types or rooms). A secondary objective is to discuss how temperature and relative humiditycan be included in the spatial position evaluation. Thirdly, the thesis aims to develop a base for furtherdiscussion regarding a method for how the sensor outputs can be combined into a single indoorenvironment quality index. The two last parts were primarily based on literature review.The conclusions drawn in this study include a general CFD model that can be modified to evaluatedifferent spatial location of VOC sensors, and general guidelines regarding placement of VOC meters inoffices or apartments. Also provided in this report is a base for further discussion concerning indoor airquality estimations by combining the provided sensor-outputs, i.e. total VOC, temperature, and relativehumidity.