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Measurement of Infiltration Rates from the Daily Cycle of Ambient CO2

Abstract A new approach for measuring air infiltration rates in buildings is proposed. The method belongs to the class of tracer gas techniques but, unlike conventional CO2 based methods that assume the outdoor ambient CO2 concentration is constant, the proposed method recognizes that photosynthesis and respiration cycle of plants and processes associated with fuel combustion produce daily, quasi-periodic, variations in the ambient CO2 concentrations. These daily variations, which are within the detection range of existing monitoring equipment, are utilized for estimating ventilation rates without the need of a source of CO2 in the building. The new method has the advantages that no tracer gas injection is needed, and time resolved results are easily obtained.