United States
               Environmental Protection
               Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
               Research and Development
EPA/600/SR-95/013   February 1995
EPA      Project  Summary
               Air  Infiltration  Measurements
               Using  Tracer  Gases:  A  Literature
               Review
               MaxM. Samfield
                 The report gives results of a litera-
               ture review of air infiltration measure-
               ments using tracer gases, including
               sulfur hexafluoride, hydrogen, carbon
               monoxide, carbon dioxide, nitrous ox-
               ide, and radioactive argon and kryp-
               ton.  Sulfur  hexafluoride  is the
               commonest tracer gas, primarily be-
               cause its presence may be accurately
               measured  in the parts per billion
               range, while most of the other gases
               used may be accurately measured in
               the  parts per million range. The re-
               port describes a computer-controlled
               injection system.
                 This Project Summary was developed
               by EPA's Air and Energy Engineering
               Research Laboratory, Research Triangle
               Park, NC, to announce key findings of
               the research project that is fully docu-
               mented in a separate report of the same
               title (see Project Report ordering infor-
               mation at back).
                 The use of tracer gases for the mea-
               surement of air  infiltration into structures
               and  interzonal flows within  a structure is
               not new. This technique has been investi-
               gated over the past 15  years. Numerous
               tracer gases have been used, among
               which are sulfur  hexafluoride, hydrogen,
               carbon monoxide, carbon dioxide, nitrous
               oxide, and radioactive argon and krypton.
Sulfur hexafluoride is the most common
tracer gas of choice—primarily because
its presence may be accurately measured
in the parts per billion range using elec-
tron  capture/gas  chromatography tech-
niques. Most of the other gases used may
be accurately measured in the parts per
million range using infrared technology.
  There  are  generally three types  of
methods used: tracer gas decay,  con-
stant concentration, and constant injec-
tion.  Investigations  comparing tracer
gases have led to the following conclu-
sions: (a) Even though sulfur hexafluo-
ride  is appreciably  heavier than  air,
mixing is not a problem; and (b) The
inherent uncontrollable variables present
in tracer gas work limit the accuracy of
determinations to +5-10%. There is thus
no reason why  one  tracer gas should
be selected over another provided other
criteria are met.  In the case of hydro-
gen,  diffusion of the gas through  the
surrounding walls can pose a problem.
  Tracer gases may be used in air flow
measurements in large  buildings where
the building  may be  treated as several
coupled zones. In such a case, the decay
technique can still be  used by having the
system repeat the injection at regular in-
tervals. A computer-controlled  injection
system is described in the full report.

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  Max M. Samfield, Durham, NC 27701, is an independent consultant.
  David C. Sanchez is the EPA Project Officer (see below).
  The complete report, entitled "Air Infiltration Measurements Using Tracer Gases: A
    Literature Review,"(Order No. PB95-173225; Cost: $17.50, subject to change)
    will be available only from
         National Technical Information Service
         5285 Port Royal Road
         Springfield, VA22161
         Telephone: 703-487-4650
  The EPA Project Officer can be contacted at
         Air and Energy Engineering Research Laboratory
         U.S. Environmental Protection Agency
         Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268

Official Business
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         EPA
   PERMIT No. G-35
EPA/600/SR-95/013

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