1、Designation: E741 11 (Reapproved 2017)Standard Test Method forDetermining Air Change in a Single Zone by Means of aTracer Gas Dilution1This standard is issued under the fixed designation E741; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers techniques using tracer gasdilution for determining a single zones air c
3、hange with theoutdoors, as induced by weather conditions and by mechanicalventilation. These techniques are: (1) concentration decay, (2)constant injection, and (3) constant concentration.1.2 This test method is restricted to any single tracer gas.The associated data analysis assumes that one can ch
4、aracterizethe tracer gas concentration within the zone with a single value.The zone shall be a building, vehicle, test cell, or anyconforming enclosure.1.3 Use of this test method requires a knowledge of theprinciples of gas analysis and instrumentation. Correct use ofthe formulas presented here req
5、uires consistent use of units,especially those of time.1.4 Determination of the contribution to air change byindividual components of the zone enclosure is beyond thescope of this test method.1.5 The results from this test method pertain only to thoseconditions of weather and zonal operation that pr
6、evailed duringthe measurement. The use of the results from this test to predictair change under other conditions is beyond the scope of thistest method.1.6 The text of this test method references notes andfootnotes which provide explanatory material. These notes andfootnotes (excluding those in tabl
7、es and figures) shall not beconsidered requirements of this test method.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices
8、 and deter-mine the applicability of regulatory limitations prior to use.1.8 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Rec
9、om-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D4480 Test Method for Measuring Surface Wind by Meansof Wind Vanes and Rotating Anemometers (Withdrawn1999)3E260 Practice for Packed Column Gas ChromatographyE63
10、1 Terminology of Building ConstructionsE779 Test Method for DeterminingAir Leakage Rate by FanPressurizationE1186 Practices for Air Leakage Site Detection in BuildingEnvelopes and Air Barrier Systems2.2 ASHRAE Documents:4ASHRAE Handbook of Fundamentals Chapter 23ASHRAE Standard 623. Terminology3.1 D
11、efinitions:3.1.1 For definitions of general terms related to buildingconstruction used in this test method, refer to TerminologyE631.3.2 Definitions of Terms Specific to This Standard:3.2.1 air change flow, Q, nthe total volume of air passingthrough the zone to and from the outdoors per unit time (m
12、3/s,m3/h, ft3/h).3.2.2 air change rate, A, nthe ratio of the total volume ofair passing through the zone to and from the outdoors per unitof time to the volume of the zone (1/s, 1/h).51This test method is under the jurisdiction of ASTM Committee E06 onPerformance of Buildings and is the direct respo
13、nsibility of Subcommittee E06.41on Air Leakage and Ventilation Performance.Current edition approved Sept. 1, 2017. Published September 2017. Originallyapproved in 1980. Last previous edition approved in 2011 as E741 11. DOI:10.1520/E0741-11R17.2For referenced ASTM standards, visit the ASTM website,
14、www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from American Society
15、of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. (ASHRAE), 1791 Tullie Circle, NE, Atlanta, GA30329, http:/www.ashrae.org.5A common way of expressing air change rate units is ACH = air changes perhour = 1 h.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoh
16、ocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organ
17、ization Technical Barriers to Trade (TBT) Committee.13.2.3 envelope, nthe system of barriers between a condi-tioned building zone and the outdoors.3.2.3.1 DiscussionThis includes exterior doors, windows,roofs, walls, floors and ductwork. It excludes interiorpartitions, ducts, and so forth, that sepa
18、rate conditioned zones.3.2.4 tracer gas, na gas that is mixed with air andmeasured in very small concentrations in order to study airmovement.3.2.5 tracer gas analyzer, na device used to measure theconcentration of tracer gas in an air sample.3.2.6 tracer gas concentration, C, nthe ratio of the quan
19、-tity of tracer gas in air to the quantity of that air (moles/moleor m3/m3).3.2.7 single zone, na space or set of spaces wherein theconcentration of a tracer gas is maintained uniformly through-out and that only exchanges air with the outside.3.2.7.1 DiscussionMultizone buildings are difficult totre
20、at as single zones and meet the uniformity of tracer gasconcentration required in this test method. Single zones withinmultizone buildings are difficult to isolate such that theyexchange air only with the outside and not to other zoneswithin the building via ventilation ducts, electrical conduits,el
21、evator shafts, stairs, and other pathways.3.3 Symbols:3.3.1 Variables:A = air change rate (1/s, 1/h).C = concentration (dimensionless).CONF = confidence limit value (units of the variable mea-sured).d = desired precision (dimensionless).ESE = estimated standard error.i = location number.k = constant
22、.n = number of data points.N = number of sampling locations in the zone.Q = flow (m3/s, m3/h, ft3/h).s = sample standard deviation (units of the variableestimated).t = a specific time (s, h).T = a period of time (s, h).V = volume (m3,ft3). = probability (dimensionless). = error (units of the variabl
23、e estimated). = coefficient of variation (dimensionless).3.3.2 Superscripts: = value at the end of the test. = mean value.3.3.3 Subscripts:A = pertaining to air change rate.avg = average.bias = pertaining to bias.C = pertaining to concentration.est = estimated.GA = pertaining to the gas analyzer.i =
24、 pertaining to time or location.inj = pertaining to the injection period.lower = lower limit.meas = pertaining to the measurement.mix = pertaining to the mixing period.precis = pertaining to precision.rep = pertaining to replicates.sample = pertaining to a discrete tracer gas or air sample.target =
25、pertaining to the desired level of tracer gas.test = pertaining to the test period.twt = weighted according to tracer gas flow.tracer = pertaining to the tracer gas.upper = upper limit.vol = pertaining to the volume of the zone.zone = pertaining to the zone under study.1 = first occurrence under dis
26、cussion.2 = last occurrence under discussion.3.3.4 Other Notations:t = time interval between periodic samples.(t) = function of time.(t, i) = function of time, t, and location, i.t(n, 1) = t-distribution value for n degrees of freedom anda two-sided probability of .4. Summary of Test Method4.1 This
27、test method uses the measurement of tracer gasdilution to determine air change within a building or otherenclosure that is characterized as a single zone. The measure-ment of the concentration, and sometimes the volume rate ofthe tracer gas that is injected into the zone, allows calculationof the vo
28、lume rate of outgoing air from the zone. From this,one can infer the volume rate of incoming air. Three techniquesare presented: (1) concentration decay, (2) constant injection,and (3) constant concentration. Each technique employs spe-cific tracer gas injection and sampling strategies. Other tech-n
29、iques exist but are beyond the scope of this test method. Table1 summarizes the three techniques.4.2 Choice of TechniqueIn choosing a technique formeasuring air change, consider the quantity to be measured, thecomparative capabilities of the techniques, and the complexityof the required equipment.4.
30、2.1 Air Change Quantity to Be MeasuredChoose be-tween direct measurement of air change rate or air change flow.Conversions between rate and flow and vice versa are subjectto the precision and bias of the measurement of the zonevolume. To obtain air change rate directly, use the tracer gasdecay techn
31、ique. To obtain air change flow, use the constantinjection or constant concentration techniques.5. Significance and Use5.1 Effects of Air ChangeAir change often accounts for asignificant portion of the heating or air-conditioning load of abuilding. It also affects the moisture and contaminant balanc
32、esin the building. Moisture-laden air passing through the buildingenvelope can permit condensation and cause material degrada-tion. An appropriate level of ventilation is required in allE741 11 (2017)2buildings; one should consult ASHRAE Standard 62 to deter-mine the ventilation requirements of a bu
33、ilding.5.2 Prediction of Air ChangeAir change depends on thesize and distribution of air leakage sites, pressure differencesinduced by wind and temperature, mechanical systemoperation, and occupant behavior. Air change may be calcu-lated from this information, however, many of the neededparameters a
34、re difficult to determine. Tracer gas testing permitsdirect measurement of air change.5.3 Utility of MeasurementMeasurements of air changeprovide useful information about ventilation and air leakage.Measurements in buildings with the ventilation system closedare used to determine whether natural air
35、 leakage rates arehigher than specified. Measurements with the ventilation sys-tem in operation are used to determine whether the air changemeets or exceeds requirements.5.4 Known ConditionsKnowledge of the factors that af-fect air change makes measurement more meaningful. Relatingbuilding response
36、to wind and temperature requires repetitionof the test under varying meteorological conditions. Relatingbuilding response to the ventilation system or to occupantbehavior requires controlled variation of these factors.5.5 Applicability of ResultsThe values for air changeobtained by the techniques us
37、ed in this test method apply to thespecific conditions prevailing at the time of the measurement.Air change values for the same building will differ if theprevailing wind and temperature conditions have changed, ifthe operation of the building is different, or if the envelopechanges between measurem
38、ents because of construction ordeterioration. To determine air leakage sites, follow PracticesE1186.5.6 Fan PressurizationA related technique (Test MethodE779) uses a fan to pressurize the building envelope. Measure-ments of corresponding air flows and pressure differencesacross the envelope charact
39、erize envelope airtightness as eitherthe air leakage rate under specified induced pressure differ-ences or the equivalent leakage area of the envelope. Thesefactors permit modeling natural air change due to wind andtemperature differences. However, direct measurement of natu-ral air change is not po
40、ssible with Test Method E779. TestMethod E779 permits comparison of different buildings, iso-lation of leakage sites, and evaluation of retrofit measures.6. Apparatus6.1 The apparatus includes means for distributing the tracergas, means for obtaining air samples, a gas analyzer to measuretracer gas
41、concentration in the air samples, and other measure-ment devices.6.2 Tracer GasSee Appendix X1 for information on tracergases and equipment used to measure their concentrations.Appendix X1 also contains tracer gas target concentrationlevels and safety information.6.2.1 Tracer Gas Concentration Stand
42、ardA known con-centration of tracer gas in air.6.3 Tracer Gas Injection and Distribution ApparatusThere are several means for releasing the appropriate volumeof tracer gas and distributing it in the zone.6.3.1 Tracer Gas Metering and Injection DevicesTheseinclude (1) a graduated syringe or other con
43、tainer of knownvolume with a means for controlled release of its contents and(2) a compressed tracer gas supply with a critical orifice, acritical orifice metering valve, an electronic mass flowcontroller, or other tracer gas flow rate measurement andcontrol device.6.3.2 Tracer Gas Distribution Devi
44、cesThese include (1)fans that permit good mixing of tracer gases injected manuallywithin the zone (oscillating or hassock fans, or, ducted forcedair systems can serve this purpose), (2) tubing networks thatdispense tracer gas via manifolds and automated valves and (3)pressure-operated valves that st
45、op the flow from a tubingnetwork when the tubing is not pressurized. (Note that leaks intubing networks release tracer gas at unintended locations.)6.4 Tracer Gas Sampling ApparatusesExamples includecontainers for manual sampling and automatic samplers thatemploy containers or networks.6.4.1 Materia
46、ls for Sampling ApparatusesSelect andcheck materials used in tracer gas sampling systems carefullyfor their reactivity and absorption of the tracer gas in use.Depending on the tracer gas, desirable materials include glass,copper, and stainless steel. Metal foil is appropriate for flexiblecontainers.
47、 Other acceptable materials include polypropylene,polyethylene, and nylon. Materials that absorb tracer gasdegrade the accuracy of the measurement. Other materialsrelease substances that interfere with tracer gas analyzeraccuracy. Depending on the tracer gas, materials to avoidinclude soft plastics,
48、 like vinyl and TFE-fluorocarbon.6.4.2 Manual SamplersThese include syringes, flexiblebottles, or air sample bags with a capacity of at least threeTABLE 1 Summary of Air Change Measurement TechniquesNOTE 1Speed of MeasurementA one-time measurement of airchange is most quickly acquired with the conce
49、ntration decay techniqueand least quickly with the constant concentration technique.NOTE 2Time-Varying Air ChangeThe constant concentration andconstant injection techniques may be useful for measuring air change ratesthat vary with time.NOTE 3Complexity of Zone GeometryWhereas all the techniquesrequire uniform tracer gas concentration, the constant concentrationtechnique may be useful to achieve this in a zone with complex geometry.NOTE 4Equipment ComplexityThe complexity of the requiredequipment is lowest for the tracer gas decay techniq
