Outdoor air delivery rates to occupants and age of air

Zhenhai Li, Jianshun S. Zhang, Leslie L. Christianson, Russell N. Kulp, Leslie E. Sparks

Research output: Contribution to journalArticlepeer-review


A simple and accurate technique to directly measure the outdoor air delivery rates to building occupants is presented. A few (two to three) measurements of tracer concentrations are sufficient for calculation. Experimental results show that the calculated outdoor air change rates from the tracer gas experiments agreed well with the outdoor airflow rates measured independently by nozzles. A relationship between the local outdoor air exchange rate and the mean age of air was derived. The proposed technique provides a way of simplifying the measurement of mean age of air and correcting experimental errors. Experimental results show that almost all the errors in the mean age of air (a maximum of 20% in our tests) caused by inaccurate timing of the start of a tracer gas step-up process (tracer buildup) can be corrected by the proposed method. The underestimated ages of air in the step-down processes (tracer decay) were also successfully corrected.

Original languageEnglish (US)
Pages (from-to)313-321
Number of pages9
JournalASHRAE Transactions
Issue number2
StatePublished - 1996
Externally publishedYes

ASJC Scopus subject areas

  • Building and Construction
  • Mechanical Engineering


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