A Review of CO2 Measurement Procedures in Ventilation Research

It is widely recognised that the carbon dioxide (CO2) concentration level inside a building is a reflection of the indoor air quality in that building. In most buildings, occupants are a major source of CO2 through exhalation. It is generally accepted that the concentration of CO2 varies with location (horizontal and vertical) within an enclosed space and this can impact on the variation of indoor air quality within the space. Hence, measurement errors related to CO2 sampling strategies in a space are important as they can lead to uncertainties in the mean concentration for the space. The aim of this paper is to investigate existing measurement practices and sampling locations and how these influence the CO2 concentrations monitored in buildings. To identify the work done in CO2 measurement practice and determine the current limitations in establishing representative locations for CO2 concentration in buildings, two main approaches were used: (i) an extensive literature review of existing knowledge from peer reviewed articles and other relevant documents (database); (ii) the use of questionnaires to identify reported measurements with CO2 sensors as representation of research methods applied by professionals and research organisations. The findings show that most researchers (based on the database and questionnaires analysed) prefer heights between 1.0 m to 1.2 m in the middle of an occupied zone as a representative location. This compares to the recognised breathing zone height of between 0.75 m to 1.8 given in the literature surveyed.