title: Air exchange rates from atmospheric CO2daily cycle.
abstract: We propose a new approach for measuring ventilation air exchange rates (AERs). The method belongs to the class of tracer gas techniques, but is formulated in the light of systems theory and signal processing. Unlike conventional CO2based methods that assume the outdoor ambient CO2concentration 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 CO2concentrations. 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 CO2in the building. Using a naturally-ventilated residential apartment, AERs obtained using the new method compared favorably (within 10%) to those obtained using the conventional CO2decay fitting technique. The new method has the advantages that no tracer gas injection is needed, and high time resolution results are obtained.
authors.affiliation: ADAI, LAETA, Department of Mechanical Engineering, University of Coimbra, 3030-788 Coimbra, Portugal.
authors.forename: João Dias
authors.initials: JD
authors.lastname: Carrilho
authors.affiliation: ADAI, LAETA, Department of Mechanical Engineering, University of Coimbra, 3030-788 Coimbra, Portugal.
authors.forename: Mário
authors.initials: M
authors.lastname: Mateus
authors.affiliation: Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI 48105, USA.
authors.forename: Stuart
authors.initials: S
authors.lastname: Batterman
authors.affiliation: ADAI, LAETA, Department of Mechanical Engineering, University of Coimbra, 3030-788 Coimbra, Portugal.
authors.forename: Manuel Gameiro
authors.initials: MG
authors.lastname: da Silva
keywords: Air exchange rate; Air infiltration; Atmospheric CO2; Hilbert transform; Time varying; Tracer gas