ASTM E1258-88(2018)
(Test Method)Standard Test Method for Airflow Calibration of Fan Pressurization Devices
Standard Test Method for Airflow Calibration of Fan Pressurization Devices
SIGNIFICANCE AND USE
5.1 The fan pressurization procedure provides a relatively fast evaluation of the airtightness of building envelopes. In order for the accuracy of the test results to be known, the airflow rate measurement technique of the fan pressurization system must be calibrated.
5.2 This test method is applicable to fan pressurization systems that are installed in an opening in the building envelope, as opposed to pressurization techniques involving the mechanical ventilation system of the building.
5.3 The technique of pressurization testing of buildings puts specific requirements on the calibration of fan pressurization systems. The calibration must cover the range of fan pressure differences (approximately 12.5 to 75 Pa) that is induced during pressurization tests. The calibration must also cover a range in fan airflow rates corresponding to the range in building size and airtightness that the fan pressurization system will encounter in the field.
5.4 The fan pressurization system must be calibrated in both directions of airflow used to pressurize and depressurize a building if the system airflow direction is reversible. These two calibrations can be conducted using the various setups described in this test method; however some of the setups can be combined such that a single calibration facility can be used to calibrate the fan in both directions. Such a single setup may involve moving the fan pressurization system from one end of the chamber to the other, reversing the orientation of the system at the same end of the chamber, or it may not require moving the system at all.
5.5 The calibration technique is applicable to the two basic types of fan pressurization systems in use, r/min doors and signal doors.
5.6 For fan pressurization systems that operate in multiple ranges of airflow rate, the system must be calibrated in each range.
5.7 The calibration technique is intended to provide a complete calibration of a fan pressurization system. After calibratin...
SCOPE
1.1 This test method covers the airflow measurement calibration techniques for fan pressurization systems used for measuring air leakage rates through building envelopes.
1.2 This test method is applicable to systems used for air leakage measurement as described in Test Method E779.
1.3 This test method involves the installation of the fan pressurization system in a calibration chamber. Use of the fan pressurization system in an actual building may introduce additional errors in the airflow measurement due to operator influence, interference of internal partitions and furnishings, weather effects, and other factors.
1.4 The proper use of this test method requires a knowledge of the principles of airflow and pressure measurement.
1.5 This standard includes two basic procedures, a preferred procedure, based on ASHRAE 51/AMCA 210, and an optional procedure based on a nonstandard airflow measurement technique, commonly used by manufacturers of fan pressurization devices, but which has not been compared with standard airflow measurement techniques.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: E1258 − 88 (Reapproved 2018)
Standard Test Method for
Airflow Calibration of Fan Pressurization Devices
This standard is issued under the fixed designation E1258; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the airflow measurement cali-
E631 Terminology of Building Constructions
bration techniques for fan pressurization systems used for
E779 Test Method for Determining Air Leakage Rate by Fan
measuring air leakage rates through building envelopes.
Pressurization
1.2 This test method is applicable to systems used for air
2.2 American Society of Heating, Refrigerating, and Air-
leakage measurement as described in Test Method E779.
Conditioning Engineers Standard:
1.3 This test method involves the installation of the fan
ASHRAE 51 ⁄AMCA 210 Laboratory Methods for Testing
pressurization system in a calibration chamber. Use of the fan
Fans for Rating
pressurization system in an actual building may introduce 4
2.3 American Society of Mechanical Engineers Standard:
additional errors in the airflow measurement due to operator
ASME MFC-3M Standard Measurement of Fluid Flow in
influence, interference of internal partitions and furnishings,
Pipes Using Orifice, Nozzle, and Venturi
weather effects, and other factors.
3. Terminology
1.4 The proper use of this test method requires a knowledge
of the principles of airflow and pressure measurement.
3.1 Definitions—For definitions used in this test method,
see Terminology E631.
1.5 This standard includes two basic procedures, a preferred
procedure, based on ASHRAE 51 ⁄AMCA 210, and an optional
3.2 Definitions of Terms Specific to This Standard:
procedure based on a nonstandard airflow measurement 3.2.1 ambient conditions, n—conditions in the space from
technique, commonly used by manufacturers of fan pressur-
which air is drawn into the calibration chamber and into which
ization devices, but which has not been compared with the chamber air is expelled.
standard airflow measurement techniques.
3.2.2 chamber, n—an enclosure of rectangular or circular
cross section to simulate the entrance and exit conditions that
1.6 The values stated in SI units are to be regarded as
the fan is expected to encounter in service.
standard. No other units of measurement are included in this
standard.
3.2.3 fan air density, n—density of air at the fan inlet
expressed in kilograms per cubic metre.
1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 3.2.4 fan airflow rate, n—volumetric airflow rate at the fan
responsibility of the user of this standard to establish appro- air density expressed in cubic metres per second.
priate safety, health, and environmental practices and deter-
3.2.5 fan outlet area, n—gross inside area measured in the
mine the applicability of regulatory limitations prior to use.
plane of the fan outlet opening expressed in square metres.
1.8 This international standard was developed in accor-
3.2.6 fan pressure difference, n—the static pressure differ-
dance with internationally recognized principles on standard-
ence between two stations expressed in pascals, measured
ization established in the Decision on Principles for the
using the static pressure taps described in Fig. 1. One station is
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. 2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
1 3
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 Performance. 30329, http://www.ashrae.org.
Current edition approved July 1, 2018. Published July 2018. Originally approved Available from American Society of Mechanical Engineers (ASME), ASME
in 1988. Last previous edition approved in 2012 as E1258 – 88 (2012). DOI: International Headquarters, Two Park Ave., New York, NY 10016-5990, http://
10.1520/E1258-88R18. www.asme.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1258 − 88 (2018)
3.2.8 fan signal, n—an output from a fan pressurization
system (other than fan speed) that is related to fan airflow rate
by the system calibration, such as the static pressure difference
across a constriction that is integral to the system.
3.2.9 fan speed, n—speed of rotation of the fan impeller
expressed in inverse seconds.
3.2.10 flow conditioners, n—a combination of screens or
perforated plates located within the calibration chamber to
reduce pressure disturbances within the chamber.
3.2.11 nozzle, n—a gradually tapered constriction, of very
precise elliptical shape, used in airflow rate measurement (see
Fig. 2).
3.2.12 nozzle chamber pressure difference, n—static pres-
sure difference measured across a nozzle or bank of nozzles
FIG. 1 Static Pressure Tap Specifications
when nozzles are installed in a chamber expressed in pascals.
3.2.13 nozzle throat diameter, n—diameter of nozzle dis-
charge end expressed in square metres.
located within the chamber between the fan and the nearest
3.2.14 nozzle throat pressure difference, n—static pressure
flow conditioners. The other station is outside the chamber.
difference across the nozzle in a duct measured with throat taps
3.2.7 fan pressurization system, n—a device for measuring
expressed in pascals (see Fig. 2).
the air leakage rate of a building envelope under controlled
3.2.15 orifice, n—a sharp-edged circular constriction used in
pressurization or depressurization of the building interior. The
airflow measurement (see Fig. 3).
system includes controllable air-moving equipment, an airflow
rate measuring system, and a device for measuring the pressure 3.2.16 orifice pressure difference, n—static pressure differ-
difference across the building envelope. Such a system is often ence measured across an orifice when the orifice is installed in
referred to as a blower door. a chamber expressed in pascals.
Nozzle with throat taps Nozzle without throat taps
NOTE 1—Nozzle throat dimension L shall be either 0.6 D 6 0.005 D (recommended) or 0.5 D 6 0.005 D .
n n n n
NOTE 2—Nozzle shall have elliptical section as shown. Two and three radii approximations to the elliptical form that do not differ at any point in the
normal direction more than 1.5 % D from the elliptical form may be used. The outlet edge of the nozzle shall be square, sharp, and free from burrs, nicks,
n
or roundings.
NOTE 3—The nozzle throat shall be measured (to an accuracy of 0.001 D ) at the minor axis of the ellipse and the nozzle exit. At each place, four
n
diameters, approximately 45° apart must be within 60.002 D of the mean. At the entrance to the throat the mean may be 0.002 D greater, but no less
n n
than the mean at the nozzle exit.
NOTE 4—The nozzle surface shall fair smoothly so that a straightedge may be rocked over the surface without clicking and the surface waves shall
not be greater than 0.001 D peak to peak.
n
NOTE 5—When nozzles are used in a chamber, either of the types shown above may be used. Where a nozzle discharges directly to a duct, nozzles
with throat taps shall be used, and the nozzle outlet should be flanged.
NOTE 6—Throat tap nozzles shall have four static pressure taps 90° apart connected to a piezometer ring.
FIG. 2 Nozzle Specifications
E1258 − 88 (2018)
FIG. 4 Transformation Piece
Recommended Plate Thickness, b
1.5 mm for d up to 150 mm
2.5 mm for d up to 300 mm
3.2 mm for d up to 600 mm
4.5 mm for d up to 1200 mm
Recommended Edge Thickness, a
Less than 0.02 d
NOTE 1—For thin plates (b < 0.02 d), there is no need for beveling the
edge of the orifice.
FIG. 3 Sharp-Edged Orifice Design
3.2.17 revolution-per-minute (r/min) door, n—a fan pressur-
ization system with a calibration that relates the fan airflow rate
to the fan speed.
3.2.18 signal door, n—a fan pressurization system with a
calibration that relates the fan airflow rate to an output signal
NOTE 1—Surface finish shall be 1 µm or better. The static orifices may
other than fan speed.
not exceed 1 mm in diameter. The minimum pitot tube stem diameter
recognized under this standard shall be 2.5 mm. In no case shall the stem
3.2.19 transformation piece, n—an element to connect a
diameter exceed ⁄30 of the test duct diameter.
duct with a measuring station to a fan when the fan connection
FIG. 5 Pitot Tube Specifications
is a different size than the duct (see Fig. 4).
4. Summary of Test Method
techniques in a duct can be used such as orifice plates (ASME
4.1 This test method contains two procedures for calibrating MFC-3M) or constant injection tracer gas methods. In order
fan pressurization devices, a preferred procedure based on for an alternative airflow rate measurement technique to be
included as a preferred procedure, the errors introduced by the
ASHRAE 51 ⁄AMCA 210, and an optional procedure employ-
ing an orifice in a chamber. procedure must be demonstrated not to exceed those intro-
duced by a nozzle or pitot traverse. In the optional procedure,
4.2 Both procedures involve the installation of the fan
the airflow is measured with a series of sharp-edged orifices
pressurization system in a chamber.
installed in the wall of the chamber.
4.3 The calibration consists of a comparison of the airflow
4.4 The calibration must include measurement points that
rate through the fan pressurization system measured by the
cover a specific range in both fan pressure difference and fan
system itself, and the airflow rate measured in the calibration
airflow rate.
facility. In the preferred procedure, three modes of airflow
measurement are acceptable: (1) a nozzle or bank of nozzles in
the chamber, (2) a traverse in a duct using a pitot tube (see Fig. 5
Persily, A. K., “Air Flow Calibration of Building Pressurization Devices,”
5), and (3) a nozzle in a duct. Other airflow rate measurement NBSIR 84-2849, National Bureau of Standards, 1984.
E1258 − 88 (2018)
5. Significance and Use Exercise care to prevent any objects from being knocked down
or blown around the test area.
5.1 The fan pressurization procedure provides a relatively
fast evaluation of the airtightness of building envelopes. In 6.3 Noise may be generated by the moving air. Make
order for the accuracy of the test results to be known, the
hearing protection equipment available for personnel involved
airflow rate measurement technique of the fan pressurization in the testing.
system must be calibrated.
6.4 Design the ducts, chamber, and other equipment utilized
5.2 This test method is applicable to fan pressurization
to withstand the pressure and other forces to be encountered.
systems that are installed in an opening in the building
envelope, as opposed to pressurization techniques involving
7. Apparatus
the mechanical ventilation system of the building.
7.1 The calibration facility must include the following
5.3 The technique of pressurization testing of buildings puts
components:
specific requirements on the calibration of fan pressurization
7.1.1 Preferred Procedure:
systems. The calibration must cover the range of fan pressure
7.1.1.1 Chamber—An enclosure of rectangular or circular
differences (approximately 12.5 to 75 Pa) that is induced
cross section with characteristic dimension, M. In the case of a
during pressurization tests. The calibration must also cover a
rectangular cross section, the height H shall be at least 2.1 m,
range in fan airflow rates corresponding to the range in
the width W shall be at least 2.4 m, and M is given by =4HW/π.
building size and airtightness that the fan pressurization system
In the case of a circular cross section, the chamber diameter
will encounter in the field.
shall be at least 2.5 m and M is equal to the chamber diameter.
5.4 The fan pressurization system must be calibrated in both When multiple nozzles are used in a chamber, the chamber
directions of airflow used to pressurize and depressurize a must be large enough to accommodate all the nozzles as
building if the system airflow direction is reversible. These two described in 7.1.2.1 and 7.1.2.2.
calibrations can be conducted using the various setups de-
7.1.1.2 Flow Conditioners—A combination of screens or
scribed in this test method; however some of the setups can be
perforated plates located in the chamber to reduce pressure
combined such that a single calibration facility can be used to
disturbances within the enclosure. These air to be located
calibrate the fan in both directions. Such a single setup may
within the chamber in accordance with 7.1.2. Where a mea-
involve moving the fan pressurization system from one end of
suring plane is located downstream of the flow conditioners,
the chamber to the other, reversing the orientation of the
the flow conditioners are provided to ensure a substantially
system at the same end of the chamber, or it may not require
uniform flow ahead of the measuring plane. Where a measur-
moving the system at all.
ing plane is located upstream of the flow conditioners, the
5.5 The calibration technique is applicable to the two basic purpose of these screens is to absorb some of the kinetic energy
types of fan pressurization systems in use, r/min doors and
of the upstream jet, and allow its normal expansion as if in an
signal doors. unconfined space. Screens of square-mesh round wire with
open areas of 50 to 60 % are suggested and several will usually
5.6 For fan pressurization systems that operate in multiple
be needed. Any combination of screens or perforated plates
ranges of airflow rate, the system must be calibrated in each
that provide this flow conditioning may be used.
range.
7.1.1.3 Airflow Rate Measurement System, for measuring
5.7 The calibration technique is intended to provide a
the fan airflow rate. Acceptable systems include a nozzle or
complete calibration of a fan pressurization system. After
bank of nozzles within the chamber, a nozzle
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E1258 − 88 (Reapproved 2012) E1258 − 88 (Reapproved 2018)
Standard Test Method for
Airflow Calibration of Fan Pressurization Devices
This standard is issued under the fixed designation E1258; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the airflow measurement calibration techniques for fan pressurization systems used for measuring
air leakage rates through building envelopes.
1.2 This test method is applicable to systems used for air leakage measurement as described in Practice Test Method E779.
1.3 This test method involves the installation of the fan pressurization system in a calibration chamber. Use of the fan
pressurization system in an actual building may introduce additional errors in the airflow measurement due to operator influence,
interference of internal partitions and furnishings, weather effects, and other factors.
1.4 The proper use of this test method requires a knowledge of the principles of airflow and pressure measurement.
1.5 This standard includes two basic procedures, a preferred procedure, based on ASHRAE 51 ⁄AMCA 210, and an optional
procedure based on a nonstandard airflow measurement technique, commonly used by manufacturers of fan pressurization devices,
but which has not been compared with standard airflow measurement techniques.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E631 Terminology of Building Constructions
E779 Test Method for Determining Air Leakage Rate by Fan Pressurization
2.2 American Society of Heating, Refrigerating, and Air-Conditioning Engineers Standard:
ASHRAE 51 ⁄AMCA 210 Laboratory Methods for Testing Fans for Rating
2.3 American Society of Mechanical Engineers Standard:
ASME MFC-3M Standard Measurement of Fluid Flow in Pipes Using Orifice, Nozzle, and Venturi
3. Terminology
3.1 Definitions—For definitions used in this test method, see Terminology E631.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 ambient conditions, n—conditions in the space from which air is drawn into the calibration chamber and into which the
chamber air is expelled.
This test method is under the jurisdiction of ASTM Committee E06 on Performance of Buildings and is the direct responsibility of Subcommittee E06.41 on Air Leakage
and Ventilation Performance.
Current edition approved Oct. 1, 2012July 1, 2018. Published October 2012July 2018. Originally approved in 1988. Last previous edition approved in 20082012 as
E1258 – 88 (2008).(2012). DOI: 10.1520/E1258-88R12.10.1520/E1258-88R18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
Available from American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. (ASHRAE), 1791 Tullie Circle, NE, Atlanta, GA 30329,
http://www.ashrae.org.
Available from American Society of Mechanical Engineers (ASME), ASME International Headquarters, ThreeTwo Park Ave., New York, NY 10016-5990,
http://www.asme.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1258 − 88 (2018)
3.2.2 chamber, n—an enclosure of rectangular or circular cross section to simulate the entrance and exit conditions that the fan
is expected to encounter in service.
3.2.3 fan air density, n—density of air at the fan inlet expressed in kilograms per cubic metre.
3.2.4 fan airflow rate, n—volumetric airflow rate at the fan air density expressed in cubic metres per second.
3.2.5 fan outlet area, n—gross inside area measured in the plane of the fan outlet opening expressed in square metres.
3.2.6 fan pressure difference, n—the static pressure difference between two stations expressed in pascals, measured using the
static pressure taps described in Fig. 1. One station is located within the chamber between the fan and the nearest flow conditioners.
The other station is outside the chamber.
3.2.7 fan pressurization system, n—a device for measuring the air leakage rate of a building envelope under controlled
pressurization or depressurization of the building interior. The system includes controllable air-moving equipment, an airflow rate
measuring system, and a device for measuring the pressure difference across the building envelope. Such a system is often referred
to as a blower door.
3.2.8 fan signal, n—an output from a fan pressurization system (other than fan speed) that is related to fan airflow rate by the
system calibration, such as the static pressure difference across a constriction that is integral to the system.
3.2.9 fan speed, n—speed of rotation of the fan impeller expressed in inverse seconds.
3.2.10 flow conditioners, n—a combination of screens or perforated plates located within the calibration chamber to reduce
pressure disturbances within the chamber.
3.2.11 nozzle, n—a gradually tapered constriction, of very precise elliptical shape, used in airflow rate measurement (see Fig.
2).
3.2.12 nozzle chamber pressure difference, n—static pressure difference measured across a nozzle or bank of nozzles when
nozzles are installed in a chamber expressed in pascals.
3.2.13 nozzle throat diameter, n—diameter of nozzle discharge end expressed in square metres.
3.2.14 nozzle throat pressure difference, n—static pressure difference across the nozzle in a duct measured with throat taps
expressed in pascals (see Fig. 2).
3.2.15 orifice, n—a sharp-edged circular constriction used in airflow measurement (see Fig. 3).
3.2.16 orifice pressure difference, n—static pressure difference measured across an orifice when the orifice is installed in a
chamber expressed in pascals.
3.2.17 revolution-per-minute (r/min) door, n—a fan pressurization system with a calibration that relates the fan airflow rate to
the fan speed.
3.2.18 signal door, n—a fan pressurization system with a calibration that relates the fan airflow rate to an output signal other
than fan speed.
3.2.19 transformation piece, n—an element to connect a duct with a measuring station to a fan when the fan connection is a
different size than the duct (see Fig. 4).
4. Summary of Test Method
4.1 This test method contains two procedures for calibrating fan pressurization devices, a preferred procedure based on
ASHRAE 51 ⁄AMCA 210, and an optional procedure employing an orifice in a chamber.
FIG. 1 Static Pressure Tap Specifications
E1258 − 88 (2018)
Nozzle with throat taps Nozzle without throat taps
NOTE 1—Nozzle throat dimension L shall be either 0.6 D 6 0.005 D (recommended) or 0.5 D 6 0.005 D .
n n n n
NOTE 2—Nozzle shall have elliptical section as shown. Two and three radii approximations to the elliptical form that do not differ at any point in the
normal direction more than 1.5 % D from the elliptical form may be used. The outlet edge of the nozzle shall be square, sharp, and free from burrs, nicks,
n
or roundings.
NOTE 3—The nozzle throat shall be measured (to an accuracy of 0.001 D ) at the minor axis of the ellipse and the nozzle exit. At each place, four
n
diameters, approximately 45° apart must be within 60.002 D of the mean. At the entrance to the throat the mean may be 0.002 D greater, but no less
n n
than the mean at the nozzle exit.
NOTE 4—The nozzle surface shall fair smoothly so that a straightedge may be rocked over the surface without clicking and the surface waves shall
not be greater than 0.001 D peak to peak.
n
NOTE 5—When nozzles are used in a chamber, either of the types shown above may be used. Where a nozzle discharges directly to a duct, nozzles
with throat taps shall be used, and the nozzle outlet should be flanged.
NOTE 6—Throat tap nozzles shall have four static pressure taps 90° apart connected to a piezometer ring.
FIG. 2 Nozzle Specifications
4.2 Both procedures involve the installation of the fan pressurization system in a chamber.
4.3 The calibration consists of a comparison of the airflow rate through the fan pressurization system measured by the system
itself, and the airflow rate measured in the calibration facility. In the preferred procedure, three modes of airflow measurement are
acceptable: (1) a nozzle or bank of nozzles in the chamber, (2) a traverse in a duct using a pitot tube (see Fig. 5), and (3) a nozzle
in a duct. Other airflow rate measurement techniques in a duct can be used such as orifice plates (ASME MFC-3M) or constant
injection tracer gas methods. In order for an alternative airflow rate measurement technique to be included as a preferred
procedure, the errors introduced by the procedure must be demonstrated not to exceed those introduced by a nozzle or pitot
traverse. In the optional procedure, the airflow is measured with a series of sharp-edged orifices installed in the wall of the chamber.
4.4 The calibration must include measurement points that cover a specific range in both fan pressure difference and fan airflow
rate.
5. Significance and Use
5.1 The fan pressurization procedure provides a relatively fast evaluation of the airtightness of building envelopes. In order for
the accuracy of the test results to be known, the airflow rate measurement technique of the fan pressurization system must be
calibrated.
5.2 This test method is applicable to fan pressurization systems that are installed in an opening in the building envelope, as
opposed to pressurization techniques involving the mechanical ventilation system of the building.
5.3 The technique of pressurization testing of buildings puts specific requirements on the calibration of fan pressurization
systems. The calibration must cover the range of fan pressure differences (approximately 12.5 to 75 Pa) that is induced during
pressurization tests. The calibration must also cover a range in fan airflow rates corresponding to the range in building size and
airtightness that the fan pressurization system will encounter in the field.
5.4 The fan pressurization system must be calibrated in both directions of airflow used to pressurize and depressurize a building
if the system airflow direction is reversible. These two calibrations can be conducted using the various setups described in this test
method; however some of the setups can be combined such that a single calibration facility can be used to calibrate the fan in both
Persily, A. K., “Air Flow Calibration of Building Pressurization Devices,” NBSIR 84-2849, National Bureau of Standards, 1984.
E1258 − 88 (2018)
Recommended Plate Thickness, b
1.5 mm for d up to 150 mm
2.5 mm for d up to 300 mm
3.2 mm for d up to 600 mm
4.5 mm for d up to 1200 mm
Recommended Edge Thickness, a
Less than 0.02 d
NOTE 1—For thin plates (b < 0.02 d), there is no need for beveling the edge of the orifice.
FIG. 3 Sharp-Edged Orifice Design
FIG. 4 Transformation Piece
directions. Such a single setup may involve moving the fan pressurization system from one end of the chamber to the other,
reversing the orientation of the system at the same end of the chamber, or it may not require moving the system at all.
5.5 The calibration technique is applicable to the two basic types of fan pressurization systems in use, r/min doors and signal
doors.
5.6 For fan pressurization systems that operate in multiple ranges of airflow rate, the system must be calibrated in each range.
E1258 − 88 (2018)
NOTE 1—Surface finish shall be 1 μm or better. The static orifices may not exceed 1 mm in diameter. The minimum pitot tube stem diameter recognized
under this standard shall be 2.5 mm. In no case shall the stem diameter exceed ⁄30 of the test duct diameter.
FIG. 5 Pitot Tube Specifications
5.7 The calibration technique is intended to provide a complete calibration of a fan pressurization system. After calibrating
several systems of an identical or similar design, the fan airflow rate may be found to be independent of certain parameters such
as fan pressure difference. Other simplifying relations between fan airflow rate and fan speed or fan signal may be observed. If
these relations are observed, a manufacturer or other calibrator may choose to simplify the calibration procedure by reducing the
number of calibration points.
5.8 The use of fan pressurization systems in actual buildings introduces additional factors that may cause errors in the airflow
rate measurement that are not accounted for by the calibration. These factors include operator and weather effects and interference
from internal partitions and other obstructions.
6. Hazards
6.1 Provide secure guards and cages for fans and motors to prevent accidental contact with any moving parts of the equipment.
6.2 When the calibration is being conducted, a large volume of air is being drawn into and forced out of the apparatus. Exercise
care to prevent any objects from being knocked down or blown around the test area.
6.3 Noise may be generated by the moving air. Make hearing protection equipment available for personnel involved in the
testing.
6.4 Design the ducts, chamber, and other equipment utilized to withstand the pressure and other forces to be encountered.
7. Apparatus
7.1 The calibration facility must include the following components:
7.1.1 Preferred Procedure:
7.1.1.1 Chamber—An enclosure of rectangular or circular cross section with characteristic dimension, M. In the case of a
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