ASTM D5157-19

Standard Guide for Statistical Evaluation of Indoor Air Quality Models

SIGNIFICANCE AND USE
4.1 Using the tools described in this guide, an individual seeking to apply an IAQ model should be able to (1) assess the performance of the model for a specific situation or (2) recognize or assess its advantages and limitations.  
4.2 This guide can also be used for identifying specific areas of model deficiency that require further development or refinement.
SCOPE
1.1 This guide provides quantitative and qualitative tools for evaluation of indoor air quality (IAQ) models. These tools include methods for assessing overall model performance as well as identifying specific areas of deficiency. Guidance is also provided in choosing data sets for model evaluation and in applying and interpreting the evaluation tools. The focus of the guide is on end results (that is, the accuracy of indoor concentrations predicted by a model), rather than operational details such as the ease of model implementation or the time required for model calculations to be performed.  
1.2 Although IAQ models have been used for some time, there is little guidance in the technical literature on the evaluation of such models. Evaluation principles and tools in this guide are drawn from past efforts related to outdoor air quality or meteorological models, which have objectives similar to those for IAQ models and a history of evaluation literature (1).2 Some limited experience exists in the use of these tools for evaluation of IAQ models.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 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.

General Information

• Status: Published
• Publication Date: 31-Jul-2019
• ICS: 07.020 - Mathematics
• ICS: 13.040.01 - Air quality in general
• Technical Committee: D22 - Air Quality
• Drafting Committee: D22.05 - Indoor Air

Relations

• Replaces: ASTM D5157-97(2014) - Standard Guide for Statistical Evaluation of Indoor Air Quality Models
• Effective Date: 01-Aug-2019
• Refers: ASTM D1356-20a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Sep-2020
• Refers: ASTM D1356-20 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Mar-2020
• Refers: ASTM D1356-15a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Oct-2015
• Refers: ASTM D1356-15 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Jul-2015
• Refers: ASTM D1356-14b - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Dec-2014
• Refers: ASTM D1356-14a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-May-2014
• Refers: ASTM D1356-14 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 15-Jan-2014
• Refers: ASTM D1356-05(2010) - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-Apr-2010
• Refers: ASTM D1356-05 - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 01-May-2005
• Refers: ASTM D1356-00a - Standard Terminology Relating to Sampling and Analysis of Atmospheres
• Effective Date: 10-Nov-2000
• Referred By: ASTM D6177-19 - Standard Practice for Determining Emission Profiles of Volatile Organic Chemicals Emitted from Bedding Sets
• Effective Date: 01-Aug-2019
• Referred By: ASTM D6178-19 - Standard Practice for Estimation of Short-Term Inhalation Exposure to Volatile Organic Chemicals Emitted from Bedding Sets
• Effective Date: 01-Aug-2019

Overview

ASTM D5157-19: Standard Guide for Statistical Evaluation of Indoor Air Quality Models provides structured methodologies for evaluating the performance of indoor air quality (IAQ) models. Developed by ASTM International, this guide offers tools to assess both the strengths and limitations of IAQ models, focusing on the accuracy of indoor pollutant concentration predictions. The standard is crucial for those involved in the development, selection, and application of IAQ models, including researchers, public health professionals, environmental engineers, and building managers.

Key Topics

• Quantitative and Qualitative Evaluation Tools
  The standard outlines statistical methods for comparing predicted concentrations to observed measurements, using:

  • Correlation coefficients
  • Regression analysis (slope, intercept)
  • Normalized mean square error (NMSE)
  • Fractional bias (FB) and bias in variance (FS)

• Model Assessment Objectives

  • Comparison of multiple models in the same scenario
  • Evaluation of a single model across different scenarios
  • Identification of model deficiencies needing further development

• Selection of Evaluation Data Sets

  • Emphasizes the importance of using independent data not involved in model development
  • Guidance on parameter selection, required temporal and spatial resolution, and best practices for obtaining reliable evaluation data

• Model Types

  • Distinguishes theoretical (based on physical principles) from empirical (statistically derived) models
  • Addresses mixed approaches and their suitability for various indoor environments and pollutants

• Considerations for Measurement Uncertainty

  • Advice on interpreting model evaluation results in the context of measurement errors and data limitations

Applications

• Model Performance Verification
  Stakeholders use ASTM D5157 to ensure that IAQ models predict indoor pollutant concentrations reliably in specific settings. This validation is vital for risk assessment and compliance with indoor air quality guidelines.

• Comparative Model Analysis
  The standard is used to compare different IAQ models or to verify how a single model performs under variable indoor conditions, such as changes in building design, ventilation strategies, or pollutant sources.

• Identifying Model Limitations
  By applying the recommended evaluation tools, users can pinpoint where an IAQ model may require revision, refinement, or further investigation.

• Support for Regulatory Compliance
  By providing a consistent and scientifically validated approach for IAQ model evaluation, ASTM D5157 supports reporting and compliance with occupational, residential, or public health standards.

Related Standards

• ASTM D1356 – Terminology Relating to Sampling and Analysis of Atmospheres: Provides definitions that underpin the tools and terms used in D5157.
• U.S. EPA Compendium of Methods for the Determination of Air Pollutants in Indoor Air – Offers recognized methods for data collection used in model evaluation.
• Other relevant guides and references:
  • Approaches for monitoring indoor air quality
  • Methodologies for statistical analysis and regression

Practical Value

Adopting ASTM D5157-19 enables a scientifically defensible approach to indoor air quality model evaluation, facilitating:

• Enhanced confidence in IAQ model predictions
• Informed decision-making for building design, health risk assessment, and policy development
• Identification and mitigation of uncertainties in predictive modeling for indoor environments

This guide is essential for anyone requiring a robust, transparent method for evaluating the accuracy and suitability of IAQ models, thus supporting improved indoor air quality management practices.

Standards Content (Sample)

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.
Designation: D5157 − 19
Standard Guide for
Statistical Evaluation of Indoor Air Quality Models
This standard is issued under the fixed designation D5157; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 Thisguideprovidesquantitativeandqualitativetoolsfor 3.1 Definitions—For definitions of terms used in this
evaluation of indoor air quality (IAQ) models. These tools standard, refer to Terminology D1356.
include methods for assessing overall model performance as 3.2 Definitions of Terms Specific to This Standard:
well as identifying specific areas of deficiency. Guidance is 3.2.1 IAQ model, n—an equation, algorithm, or series of
alsoprovidedinchoosingdatasetsformodelevaluationandin equations/algorithmsusedtocalculateaverageortime-varying
applyingandinterpretingtheevaluationtools.Thefocusofthe pollutant concentrations in one or more indoor chambers for a
guide is on end results (that is, the accuracy of indoor specific situation.
concentrations predicted by a model), rather than operational
3.2.2 model chamber, n—an indoor airspace of defined
details such as the ease of model implementation or the time
volume used in model calculations; IAQ models can be
required for model calculations to be performed.
specified for a single chamber or for multiple, interconnected
chambers.
1.2 Although IAQ models have been used for some time,
there is little guidance in the technical literature on the
3.2.3 model evaluation, n—aseriesofstepsthroughwhicha
evaluation of such models. Evaluation principles and tools in
model developer or user assesses a model’s performance for
this guide are drawn from past efforts related to outdoor air
selected situations.
quality or meteorological models, which have objectives simi-
3.2.4 model parameter, n—a mathematical term in an IAQ
lar to those for IAQ models and a history of evaluation
model that must be estimated by the model developer or user
literature (1). Some limited experience exists in the use of
before model calculations can be performed.
these tools for evaluation of IAQ models.
3.2.5 model residual, n—the difference between an indoor
1.3 The values stated in SI units are to be regarded as
concentration predicted by an IAQ model and a representative
standard. No other units of measurement are included in this
measurement of the indoor concentration; the value should be
standard.
stated as positive or negative.
1.4 This international standard was developed in accor-
3.2.6 model validation, n—a series of evaluations under-
dance with internationally recognized principles on standard-
taken by an agency or organization to provide a basis for
ization established in the Decision on Principles for the
endorsing a specific model (or models) for a specific applica-
Development of International Standards, Guides and Recom-
tion (or applications).
mendations issued by the World Trade Organization Technical
3.2.7 observed model bias, n—a systematic difference be-
Barriers to Trade (TBT) Committee.
tween model predictions and measured indoor concentrations
indicatedbymodelresidual(forexample,themodelprediction
2. Referenced Documents
3 is generally higher than the measured concentration for a
2.1 ASTM Standards:
specific situation).
D1356Terminology Relating to Sampling and Analysis of
3.2.8 pollutant concentration, n—the extent of the occur-
Atmospheres
rence of a pollutant or the parameters describing a pollutant in
a defined airspace, expressed in units characteristic to the
This guide is under the jurisdiction of ASTM Committee D22 on Air Quality
3 3 3
pollutant(forexample,mg/m ,ppm,Bq/m ,area/m ,orcolony
and is the direct responsibility of Subcommittee D22.05 on Indoor Air.
Current edition approved Aug. 1, 2019. Published September 2019. Originally
forming units per cubic metre).
approved in 1991. Last previous edition approved in 2008 as D5157–97 (2014).
DOI: 10.1520/D5157-19.
4. Significance and Use
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard.
4.1 Using the tools described in this guide, an individual
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
seekingtoapplyanIAQmodelshouldbeableto(1)assessthe
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
performance of the model for a specific situation or (2)
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. recognize or assess its advantages and limitations.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5157 − 19
4.2 Thisguidecanalsobeusedforidentifyingspecificareas at different times within the same structure, or both. Theoreti-
of model deficiency that require further development or refine- cal models will generally be suitable for a wide range of
ment. applications, whereas empirical models will generally be
applicable only within the range of measurements from which
5. Components of Model Evaluation
they were developed.
5.1 The components of model evaluation include the fol-
5.1.2.4 Somecombinationoftheoreticalandempiricalcom-
lowing: (1) stating the purpose(s) or objective(s) of the
ponents is also possible. Specific parameters of a theoretical
evaluation, (2) acquiring a basic understanding of the specifi-
model may have relationships with other factors that can be
cation and underlying principles or assumptions, (3) selecting
more easily quantified than the parameters themselves. For
data sets as inputs to the evaluation process, and (4) selecting
example, the rate of air infiltration into a structure could
and using appropriate tools for assessing model performance.
dependonoutdoorwindspeedandtheindoor-outdoortempera-
Just as model evaluation has multiple components, model
ture difference, or the emission rate from a cigarette could
validation consists of one or more evaluations. However,
depend on the combustion rate and the constituents of the
model validation is beyond the scope of this document.
particular brand smoked. Given sufficient data, such relation-
5.1.1 Establishing Evaluation Objectives:
shipscouldbeestimatedthroughtechniquessuchasregression
5.1.1.1 IAQmodelsaregenerallyusedforthefollowing:(1)
analysis.
to help explain the temporal and spatial variations in the
5.1.2.5 IAQ models may be specified for a particular pol-
occurrences of indoor pollutant concentrations, (2) to improve
lutant or in general terms; this distinction is important, for
the understanding of major influencing factors or underlying
example, because particle-phase pollutants behave differently
physical/chemical processes, and (3) to predict the temporal/
from gas-phase pollutants. Particulate matter is subject to
spatialvariationsinindoorconcentrationsthatcanbeexpected
coagulation, chemical reaction at surfaces, gravitational
to occur in specific types of situations. However, model
settling, diffusional deposition, resuspension and interception,
evaluation relates only to the third type of model use—
impaction, and diffusional removal by filtration devices;
prediction of indoor concentrations.
whereassomegaseouspollutantsaresubjecttosorptionand,in
5.1.1.2 The most common evaluation objectives are (1)to
some cases, desorption processes.
compare the performance of two or more models for a specific
5.1.2.6 Dynamic IAQ models predict time-varying indoor
situation or set of situations and (2) to assess the performance
concentrations for time steps that are usually on the order of
of a specific model for different situations. Secondary objec-
seconds, minutes, or hours; whereas integrated models predict
tives include identifying specific areas of model deficiency.
time-averaged indoor concentrations using average values for
Determination of specific objectives will assist in choosing
each input parameter or averaging these parameters during the
appropriate data sets and quantitative or qualitative tools for
course of exercising the model. Models can also differ in the
model evaluation.
extent of partitioning of the indoor airspace, with the simplest
5.1.2 Understanding the Model(s) to be Evaluated:
modelstreatingtheentireindoorvolumeasasinglechamberor
5.1.2.1 Although a model user will not necessarily know or
zone assumed to have homogeneous concentrations through-
understand all details of a particular model, some fundamental
out; more complex models can treat the indoor volume as a
understanding of the underlying principles and concepts is
series of interconnected chambers, with a mass balance con-
important to the evaluation process. Thus, before evaluating a
ducted without each chamber and consideration given to
model, the user should develop some understanding of the
communicating airflows among chambers.
basis for the model and its operation. IAQ models can
5.1.2.7 Generally speaking, as the model complexity grows
generally be distinguished by their basis, by the range of
in terms of temporal detail, number of chambers, and types of
pollutants they can address, and by the extent of temporal or
parameters that can be used for calculations, the user’s task of
spatialdetailtheycanaccommodateininputs,calculations,and
supplyingappropriateinputsbecomesincreasinglydemanding.
outputs.
Thus users must have a basic understanding of the underlying
5.1.2.2 Theoretical models are generally based on physical
principles, nature and extent of inputs required, inherent
principles such as mass conservation (2, 3). That is, a mass
limitations, and types of outputs provided so that they can
balance is maintained to keep track of material entering and
choose a level of model complexity providing an appropriate
leaving a particular airspace. Within this conceptual
balance between input effort and output detail.
framework, pollutant concentrations are increased by emis-
sions within the defined volume and by transport from other 5.1.2.8 A number of assumptions are usually made when
airspaces, including outdoors. Similarly, concentrations are modeling a complex environment such as the indoor airspace.
decreased by transport exiting the airspace, by removal to These assumptions, and their potential influence on the mod-
chemical/physical sinks within the airspace, or for reactive eling results, should be identified in the evaluation process.
species, by conversion to other forms. Relationships are most One method of gaining insights is by performing sensitivity
often specified through a differential equation quantifying analysis.Anexampleofthistechniqueistosystematicallyvary
factors related to contaminant gain or loss. the values of one input parameter at a time to determine the
5.1.2.3 Empirical models (3) are generally based on ap- effect of each on the modeling results; each parameter should
proaches such as linear regression analysis, using measure- be varied over a reasonable range of values likely to be
ments under different conditions across a variety of structures, encountered for the specific situation(s) of interest.
--
...

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: D5157 − 97 (Reapproved 2014) D5157 − 19
Standard Guide for
Statistical Evaluation of Indoor Air Quality Models
This standard is issued under the fixed designation D5157; 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 guide provides quantitative and qualitative tools for evaluation of indoor air quality (IAQ) models. These tools include
methods for assessing overall model performance as well as identifying specific areas of deficiency. Guidance is also provided in
choosing data sets for model evaluation and in applying and interpreting the evaluation tools. The focus of the guide is on end
results (that is, the accuracy of indoor concentrations predicted by a model), rather than operational details such as the ease of
model implementation or the time required for model calculations to be performed.
1.2 Although IAQ models have been used for some time, there is little guidance in the technical literature on the evaluation of
such models. Evaluation principles and tools in this guide are drawn from past efforts related to outdoor air quality or
meteorological models, which have objectives similar to those for IAQ models and a history of evaluation literature.literature (1)).
Some limited experience exists in the use of these tools for evaluation of IAQ models.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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:
D1356 Terminology Relating to Sampling and Analysis of Atmospheres
3. Terminology
3.1 Definitions:Definitions For —For definitions of terms used in this standard, refer to Terminology D1356.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 IAQ model, n—an equation, algorithm, or series of equations/algorithms used to calculate average or time-varying
pollutant concentrations in one or more indoor chambers for a specific situation.
3.2.2 model bias, n—a systematic difference between model predictions and measured indoor concentrations (for example, the
model prediction is generally higher than the measured concentration for a specific situation).
3.2.2 model chamber, n—an indoor airspace of defined volume used in model calculations; IAQ models can be specified for a
single chamber or for multiple, interconnected chambers.
3.2.3 model evaluation, n—a series of steps through which a model developer or user assesses a model’smodel’s performance
for selected situations.
3.2.4 model parameter, n—a mathematical term in an IAQ model that must be estimated by the model developer or user before
model calculations can be performed.
3.2.5 model residual, n—the difference between an indoor concentration predicted by an IAQ model and a representative
measurement of the true indoor concentration; the value should be stated as positive or negative.
3.2.6 model validation, n—a series of evaluations undertaken by an agency or organization to provide a basis for endorsing a
specific model (or models) for a specific application (or applications).
This guide is under the jurisdiction of ASTM Committee D22 on Air Quality and is the direct responsibility of Subcommittee D22.05 on Indoor Air.
Current edition approved Sept. 1, 2014Aug. 1, 2019. Published September 2014September 2019. Originally approved in 1991. Last previous edition approved in 2008
as D5157 – 97 (2008).(2014). DOI: 10.1520/D5157-97R14.10.1520/D5157-19.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5157 − 19
3.2.7 observed model bias, n—a systematic difference between model predictions and measured indoor concentrations indicated
by model residual (for example, the model prediction is generally higher than the measured concentration for a specific situation).
3.2.8 pollutant concentration, n—the extent of the occurrence of a pollutant or the parameters describing a pollutant in a defined
3 3 3
airspace, expressed in units characteristic to the pollutant (for example, mg/m , ppm, Bq/m , area/m , or colony forming units per
cubic metre).
4. Significance and Use
4.1 Using the tools described in this guide, an individual seeking to apply an IAQ model should be able to (1) assess the
performance of the model for a specific situation or (2) recognize or assess its advantages and limitations.
4.2 This guide can also be used for identifying specific areas of model deficiency that require further development or refinement.
5. Components of Model Evaluation
5.1 The components of model evaluation include the following: (1) stating the purpose(s) or objective(s) of the evaluation, (2)
acquiring a basic understanding of the specification and underlying principles or assumptions, (3) selecting data sets as inputs to
the evaluation process, and (4) selecting and using appropriate tools for assessing model performance. Just as model evaluation
has multiple components, model validation consists of one or more evaluations. However, model validation is beyond the scope
of this document.
5.1.1 Establishing Evaluation Objectives:
5.1.1.1 IAQ models are generally used for the following: (1) to help explain the temporal and spatial variations in the
occurrences of indoor pollutant concentrations, (2) to improve the understanding of major influencing factors or underlying
physical/chemical processes, and (3) to predict the temporal/spatial variations in indoor concentrations that can be expected to
occur in specific types of situations. However, model evaluation relates only to the third type of model use—prediction of indoor
concentrations.
5.1.1.2 The most common evaluation objectives are (1) to compare the performance of two or more models for a specific
situation or set of situations and (2) to assess the performance of a specific model for different situations. Secondary objectives
include identifying specific areas of model deficiency. Determination of specific objectives will assist in choosing appropriate data
sets and quantitative or qualitative tools for model evaluation.
5.1.2 Understanding the Model(s) to be Evaluated:
5.1.2.1 Although a model user will not necessarily know or understand all details of a particular model, some fundamental
understanding of the underlying principles and concepts is important to the evaluation process. Thus, before evaluating a model,
the user should develop some understanding of the basis for the model and its operation. IAQ models can generally be
distinguished by their basis, by the range of pollutants they can address, and by the extent of temporal or spatial detail they can
accommodate in inputs, calculations, and outputs.
5.1.2.2 Theoretical models are generally based on physical principles such as mass conservation.conservation (2, 3)). That is,
a mass balance is maintained to keep track of material entering and leaving a particular airspace. Within this conceptual framework,
pollutant concentrations are increased by emissions within the defined volume and by transport from other airspaces, including
outdoors. Similarly, concentrations are decreased by transport exiting the airspace, by removal to chemical/physical sinks within
the airspace, or for reactive species, by conversion to other forms. Relationships are most often specified through a differential
equation quantifying factors related to contaminant gain or loss.
5.1.2.3 Empirical models (3) are generally based on approaches such as least-squareslinear regression analysis, using
measurements under different conditions across a variety of structures, at different times within the same structure, or both.
Theoretical models will generally be suitable for a wide range of applications, whereas empirical models will generally be
applicable only within the range of measurements from which they were developed.
5.1.2.4 Some combination of theoretical and empirical components is also possible. Specific parameters of a theoretical model
may have relationships with other factors that can be more easily quantified than the parameters themselves. For example, the rate
of air infiltration into a structure could depend on outdoor windspeed and the indoor-outdoor temperature difference, or the
emission rate from a cigarette could depend on the combustion rate and the constituents of the particular brand smoked. Given
sufficient data, such relationships could be estimated through techniques such as regression analysis.
5.1.2.5 IAQ models may be specified for a particular pollutant or in general terms; this distinction is important, for example,
because particle-phase pollutants behave differently from gas-phase pollutants. Particulate matter is subject to coagulation,
chemical reaction at surfaces, gravitational settling, diffusional deposition, resuspension and interception, impaction, and
diffusional removal by filtration devices; whereas some gaseous pollutants are subject to sorption and, in some cases, desorption
processes.
5.1.2.6 Dynamic IAQ models predict time-varying indoor concentrations for time steps that are usually on the order of seconds,
minutes, or hours; whereas integrated models predict time-averaged indoor concentrations using average values for each input
parameter or averaging these parameters during the course of exercising the model. Models can also differ in the extent of
partitioning of the indoor airspace, with the simplest models treating the entire indoor volume as a single chamber or zone assumed
D5157 − 19
to have homogeneous concentrations throughout; more complex models can treat the indoor volume as a series of interconnected
chambers, with a mass balance conducted without each chamber and consideration given to communicating airflows among
chambers.
5.1.2.7 Generally speaking, as the model complexity grows in terms of temporal detail, number of chambers, and types of
parameters that can be used for calculations, the user’suser’s task of supplying appropriate inputs becomes increasingly
demanding. Thus users must have a basic understanding of the underlying principles, nature and extent of inputs required, inherent
limitations, and types of outputs provided so that they can choose a level of model complexity providing an appropriate balance
between input effort and output detail.
5.1.2.8 A number of assumptions are usually made when modeling a complex environment such as the indoor airspace. These
assumptions, and their potential influence on the modeling results, should be identified in the evaluation process. One method of
gaining insights is by performing sensitivity analysis. An example of this technique is to systematically vary the values of one input
parameter at a time to determine the effect of each on the modeling results; each parameter should be varied over a reasonable range
of values likely to be encountered for the specific situation(s) of interest.
D5157 − 19
5.1.3 Choosing Data Sets for Model Evaluation:
5.1.3.1 A fundamental requirement for model evaluation is that the data used for the evaluation process should be independent
of the data used to develop the model. This constraint forces a search for available data pertinent to the planned application or,
if no appropriate data sets can be found, collection of new data to support the evaluation process. Such data should be collected
according to commonly recognized and accepted methods, such as those given in the compendium developed by the U.S.
Environmental Protection Agency (4).
5.1.3.2 The following series of steps should be used in choosing data sets for model evaluation: (1) select situations for applying
and testing the model; (2) note the model input parameters that require estimation for the situations selected; (3) determine the
required levels of temporal detail (for example, minute-by-minute or hour-by-hour) and spatial detail (that is, number of chambers)
for model application as well as variations of the contaminants within each chamber; and (4) find or collect appropriate data for
estimation of the model inputs and comparison with the mode
...