Evaluation of the potential of water vapor to be used as a tracer gas for determining air change rates

Conventional tracer gas testing, using conservative tracer gases (like SF6 or CO2), is the most accurate method for assessing air change rates, but it can be expensive and cumbersome to perform. Using water vapor as unconventional tracer gas has been proposed as an alternative, but it has not been broadly validated through the build environment. This paper evaluates water vapor tracer gas testing in a new context. Eight simultaneous water vapor and CO2 tracer gas tests were conducted on a Mongolian ger (or “yurt” in Russian). The air change rates from the water vapor (ACHH2O) and CO2 tracer gas tests (ACHCO2) were compared to evaluate the accuracy of the method. Under ideal conditions, the ACHH2O values were accurate within 21–41% of the ACHCO2 values (consistent with the literature). Indoor combustion and rainstorms were identified to cause higher errors (70–88% and 76%, respectively). Limitations in the accuracy and deployment of the sensors made characterization of the air change rate (ACH) errors challenging. However, the agreement between the ACHH2O and ACHCO2 observed in this study was consistent with other lower cost alternatives to conventional tracer gas testing. This paper evaluates water vapor tracer gas testing in a new residential building type, and it is the first study to consider water vapor tracer gas testing in the presence of indoor combustion and after a rainstorm.