ASTM E741-00(2006)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E 741 – 00 (Reapproved 2006)
Standard Test Method for
Determining Air Change in a Single Zone by Means of a
Tracer Gas Dilution
This standard is issued under the fixed designation E741; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method covers techniques using tracer gas 2.1 ASTM Standards:
dilution for determining a single zone’s air change with the D4480 Test MEthod for MEasuring Surface Wind by
outdoors, as induced by weather conditions and by mechanical Means of Wind Vanes and Rotating Anemometers
ventilation. These techniques are: (1) concentration decay, (2) E260 Practice for Packed Column Gas Chromatography
constant injection, and (3) constant concentration. E779 Test Method for Determining Air Leakage Rate by
1.2 This test method is restricted to any single tracer gas. Fan Pressurization
The associated data analysis assumes that one can characterize E1186 PracticesforAirLeakageSiteDetectioninBuilding
thetracergasconcentrationwithinthezonewithasinglevalue. Envelopes and Air Barrier Systems
The zone shall be a building, vehicle, test cell, or any 2.2 Other Documents:
conforming enclosure. ASHRAE Handbook of Fundamentals, Chapter 23
1.3 Use of this test method requires a knowledge of the ASHRAE Standard62
principles of gas analysis and instrumentation. Correct use of
3. Terminology
the formulas presented here requires consistent use of units,
3.1 Definitions of Terms Specific to This Standard:
especially those of time.
1.4 Determination of the contribution to air change by 3.1.1 air change flow, Q, n—the total volume of air passing
through the zone to and from the outdoors per unit time (m /s,
individual components of the zone enclosure is beyond the
3 3
scope of this test method. m /h, ft /h).
3.1.2 air change rate, A, n—the ratio of the total volume of
1.5 The results from this test method pertain only to those
air passing through the zone to and from the outdoors per unit
conditionsofweatherandzonaloperationthatprevailedduring
themeasurement.Theuseoftheresultsfromthistesttopredict of time to the volume of the zone (1/s, 1/h).
3.1.3 envelope, n—the system of barriers between a condi-
air change under other conditions is beyond the scope of this
test method. tioned building zone and the outdoors.
3.1.3.1 Discussion—This includes exterior doors, windows,
1.6 The text of this test method references notes and
footnoteswhichprovideexplanatorymaterial.Thesenotesand roofs, walls, floors and ductwork. It excludes interior parti-
tions, ducts, and so forth, that separate conditioned zones.
footnotes (excluding those in tables and figures) shall not be
considered requirements of this test method. 3.1.4 tracer gas, n—a gas that is mixed with air and
measured in very small concentrations in order to study air
1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the movement.
3.1.5 tracer gas analyzer, n—a device used to measure the
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- concentration of tracer gas in an air sample.
bility of regulatory limitations prior to use.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contactASTM Customer Service at service@astm.org. ForAnnual Book ofASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
Withdrawn.
1 4
This test method is under the jurisdiction of ASTM Committee E06 on Available from American Society of Heating, Refrigerating, and Air-
Performance of Buildings and is the direct responsibility of Subcommittee E06.41 Conditioning Engineers, Inc. (ASHRAE), 1791 Tullie Circle, NE, Atlanta, GA
on Air Leakage and Ventilation. 30329, http://www.ashrae.org.
Current edition approved Oct. 1, 2006. Published October 2006. Originally A common way of expressing air change rate units is ACH=air changes per
approved in 1980. Last previous edition approved in 2000 as E741–00. hour=1/h.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 741 – 00 (2006)
3.1.6 tracer gas concentration, C, n—the ratio of the
twt = weighted according to tracer gas flow.
quantity of tracer gas in air to the quantity of that air
tracer = pertaining to the tracer gas.
3 3
(moles/mole or m /m ).
upper = upper limit.
vol = pertaining to the volume of the zone.
3.1.7 single zone, n—a space or set of spaces wherein the
zone = pertaining to the zone under study.
concentration of a tracer gas is maintained uniformly through-
1 = first occurrence under discussion.
out and that only exchanges air with the outside.
2 = last occurrence under discussion.
3.1.7.1 Discussion—Multizone buildings are difficult to
3.2.4 Other Notations:
treat as single zones and meet the uniformity of tracer gas
concentration required in this test method. Single zones within
multizone buildings are difficult to isolate such that they
Dt = time interval between periodic samples.
exchange air only with the outside and not to other zones
(t) = function of time.
within the building via ventilation ducts, electrical conduits,
(t, i) = function of time, t, and location, i.
elevator shafts, stairs, and other pathways.
t(n, = t-distribution value for n degrees of freedom
1−a) and a two-sided probability of a.
3.2 Symbols:
3.2.1 Variables:
4. Summary of Test Method
4.1 This test method uses the measurement of tracer gas
A = air change rate (1/s, 1/h).
dilution to determine air change within a building or other
C = concentration (dimensionless).
enclosure that is characterized as a single zone. The measure-
CONF = confidence limit value (units of the variable mea-
ment of the concentration, and sometimes the volume rate of
sured).
the tracer gas that is injected into the zone, allows calculation
d = desired precision (dimensionless).
of the volume rate of outgoing air from the zone. From this,
ESE = estimated standard error.
onecaninferthevolumerateofincomingair.Threetechniques
i = location number.
are presented: (1) concentration decay, (2) constant injection,
k = constant.
and (3) constant concentration. Each technique employs spe-
n = number of data points.
cific tracer gas injection and sampling strategies. Other tech-
N = number of sampling locations in the zone.
3 3 3
niquesexistbutarebeyondthescopeofthistestmethod.Table
Q = flow (m /s, m /h, ft /h).
1 summarizes the three techniques.
s = sample standard deviation (units of the variable
4.2 Choice of Technique—In choosing a technique for
estimated).
t = a specific time (s, h). measuringairchange,considerthequantitytobemeasured,the
T = a period of time (s, h). comparative capabilities of the techniques, and the complexity
3 3
V = volume (m,ft ).
of the required equipment.
a = probability (dimensionless).
4.2.1 Air Change Quantity to Be Measured—Choose be-
e = error (units of the variable estimated).
tweendirectmeasurementofairchangerateorairchangeflow.
n = coefficient of variation (dimensionless).
3.2.2 Superscripts:
TABLE 1 Summary of Air Change Measurement Techniques
NOTE 1—Speed of Measurement—A one-time measurement of air
change is most quickly acquired with the concentration decay technique
8 = value at the end of the test.
and least quickly with the constant concentration technique.
− = mean value.
NOTE 2—Time-Varying Air Change—The constant concentration and
constantinjectiontechniquesmaybeusefulformeasuringairchangerates
3.2.3 Subscripts:
that vary with time.
NOTE 3—Complexity of Zone Geometry—Whereas all the techniques
require uniform tracer gas concentration, the constant concentration
A = pertaining to air change rate.
techniquemaybeusefultoachievethisinazonewithcomplexgeometry.
avg = average.
NOTE 4—Equipment Complexity—The complexity of the required
bias = pertaining to bias.
equipment is lowest for the tracer gas decay technique and highest for the
C = pertaining to concentration.
constant concentration technique.
est = estimated.
Type of Air Steady-State Concentration
Tech- Volume Control of
GA = pertaining to the gas analyzer.
Change Mea- Assumption Measurement
nique Tracer Gas
surement Required? Relative To
i = pertaining to time or location.
Concentration Decay—Section 8
inj = pertaining to the injection period.
Average Rate No Approximate initial- Other samples
lower = lower limit.
target
meas = pertaining to the measurement.
Regres- Rate Yes Approximate initial Other samples
sion target
mix = pertaining to the mixing period.
Constant Injection—Section 9
precis = pertaining to precision.
Average Flow No Flow rate to within Absolute stan-
rep = pertaining to replicates.
2% dard
sample = pertaining to a discrete tracer gas or air sample. Constant Concentration—Section 10
Flow No Mean concentration Absolute stan-
target = pertaining to the desired level of tracer gas.
within2%oftarget dard
test = pertaining to the test period.
E 741 – 00 (2006)
Conversions between rate and flow and vice versa are subject 6. Apparatus
to the precision and bias of the measurement of the zone
6.1 The apparatus includes means for distributing the tracer
volume. To obtain air change rate directly, use the tracer gas
gas,meansforobtainingairsamples,agasanalyzertomeasure
decay technique. To obtain air change flow, use the constant
tracer gas concentration in the air samples, and other measure-
injection or constant concentration techniques.
ment devices.
6.2 Tracer Gas—See Appendix X1 for information on
5. Significance and Use tracer gases and equipment used to measure their concentra-
tions. Appendix X1 also contains tracer gas target concentra-
5.1 Effects of Air Change—Air change often accounts for a
tion levels and safety information.
significant portion of the heating or air-conditioning load of a
6.2.1 Tracer Gas Concentration Standard—A known con-
building. It also affects the moisture and contaminant balances
centration of tracer gas in air.
inthebuilding.Moisture-ladenairpassingthroughthebuilding
6.3 Tracer Gas Injection and Distribution Apparatus—
envelope can permit condensation and cause material degrada-
There are several means for releasing the appropriate volume
tion. An appropriate level of ventilation is required in all
of tracer gas and distributing it in the zone.
buildings; one should consult ASHRAE Standard62 to deter-
6.3.1 Tracer Gas Metering and Injection Devices—These
mine the ventilation requirements of a building.
include (1) a graduated syringe or other container of known
5.2 Prediction of Air Change—Air change depends on the
volume with a means for controlled release of its contents and
size and distribution of air leakage sites, pressure differences
(2) a compressed tracer gas supply with a critical orifice, a
induced by wind and temperature, mechanical system opera-
criticalorificemeteringvalve,anelectronicmassflowcontrol-
tion, and occupant behavior. Air change may be calculated ler, or other tracer gas flow rate measurement and control
device.
from this information, however, many of the needed param-
6.3.2 Tracer Gas Distribution Devices—These include (1)
etersaredifficulttodetermine.Tracergastestingpermitsdirect
fans that permit good mixing of tracer gases injected manually
measurement of air change.
within the zone (oscillating or hassock fans, or, ducted forced
5.3 Utility of Measurement—Measurements of air change
air systems can serve this purpose), (2) tubing networks that
provide useful information about ventilation and air leakage.
dispensetracergasviamanifoldsandautomatedvalvesand(3)
Measurements in buildings with the ventilation system closed
pressure-operated valves that stop the flow from a tubing
are used to determine whether natural air leakage rates are
network when the tubing is not pressurized. (Note that leaks in
higher than specified. Measurements with the ventilation sys-
tubing networks release tracer gas at unintended locations.)
tem in operation are used to determine whether the air change
6.4 Tracer Gas Sampling Apparatuses—Examples include
meets or exceeds requirements.
containers for manual sampling and automatic samplers that
5.4 Known Conditions—Knowledge of the factors that af-
employ containers or networks.
fectairchangemakesmeasurementmoremeaningful.Relating
6.4.1 Materials for Sampling Apparatuses—Select and
building response to wind and temperature requires repetition
check materials used in tracer gas sampling systems carefully
of the test under varying meteorological conditions. Relating
for their reactivity and absorption of the tracer gas in use.
building response to the ventilation system or to occupant
Depending on the tracer gas, desirable materials include glass,
behavior requires controlled variation of these factors. copper,andstainlesssteel.Metalfoilisappropriateforflexible
containers. Other acceptable materials include polypropylene,
5.5 Applicability of Results—The values for air change
polyethylene, and nylon. Materials that absorb tracer gas
obtainedbythetechniquesusedinthistestmethodapplytothe
degrade the accuracy of the measurement. Other materials
specific conditions prevailing at the time of the measurement.
release substances that interfere with tracer gas analyzer
Air change values for the same building will differ if the
accuracy. Depending on the tracer gas, materials to avoid
prevailing wind and temperature conditions have changed, if
include soft plastics, like vinyl and TFE-fluorocarbon.
the operation of the building is different, or if the envelope
6.4.2 Manual Samplers—These include syringes, flexible
changes between measurements because of construction or
bottles, or air sample bags with a capacity of at least three
deterioration. To determine air leakage sites, follow Practice
timestheminimumsamplesizeofthegasanalyzerused.These
E1186.
containers shall have an airtight seal to assure that the sample
5.6 Fan Pressurization—A related technique (Test Method
is not diluted or contaminated. Each container shall have a
E779) uses a fan to pressurize the building envelope. Mea-
labelthatkeysittoarecordofthetimeandlocationthatitwas
surements of corresponding air flows and pressure differences
used. Do not reuse sample containers without first confirming
acrosstheenvelopecharacterizeenvelopeairtightnessaseither
that they are not contaminated with tracer gas.
the air leakage rate under specified induced pressure differ-
6.4.3 Automatic Samplers—These apparatuses comprise
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