ASTM D7297-21

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: D7297 − 21
Standard Practice for
Evaluating Residential Indoor Air Quality Concerns
This standard is issued under the fixed designation D7297; 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 and appliances; use of IAQ measurement equipment; interpre-
tation of IAQ data; and technical report writing.
1.1 This standard practice describes procedures for evaluat-
ing indoor air quality (IAQ) concerns in residential buildings. 1.7 Although many elements described in this standard
practice may be useful in training of IAQ investigators, it
1.2 The practice primarily addresses IAQ concerns encoun-
should not be used as the sole basis for specifying or
tered in single-family detached and attached (for example,
conducting such training.
townhouse or duplex design) residential buildings. Limited
1.8 This standard does not purport to address all of the
guidance is also provided for low- and high-rise multifamily
safety concerns, if any, associated with its use. It is the
dwellings, such as condominiums and apartments.
responsibility of the user of this standard to establish appro-
1.3 The IAQ evaluation procedures are comprised of inter-
priate safety, health, and environmental practices and deter-
views with the homeowner or resident(s) (including telephone
mine the applicability of regulatory limitations prior to use.
interviews and face-to-face meetings) and on-site investiga-
For additional safety precautionary information, see Section 6.
tions (including walk-through, assessment, and measure-
1.9 This international standard was developed in accor-
ments). For application practicality, these procedures are di-
dance with internationally recognized principles on standard-
vided into three separate phases, which may occur over one or
ization established in the Decision on Principles for the
more site visits.
Development of International Standards, Guides and Recom-
1.4 The procedures described in this standard practice are
mendations issued by the World Trade Organization Technical
aimed at identifying potential causes contributing to an IAQ
Barriers to Trade (TBT) Committee.
issue or concern. Such findings can be the basis for recom-
mending corrective measures. This standard practice does not 2. Referenced Documents
describe problem resolution or corrective measures, and the 2
2.1 ASTM Standards:
standard is not intended to evaluate the impact of corrective
D1356 Terminology Relating to Sampling and Analysis of
measures.
Atmospheres
1.5 This practice describes a pathway for characterizing
D1357 Practice for Planning the Sampling of the Ambient
indoorair,thoughusingthispracticedoesnotguaranteethatan Atmosphere
investigator will be able to identify or resolve an IAQ D4861 Practice for Sampling and Selection of Analytical
complaint for one or more of the following reasons: (1) the Techniques for Pesticides and Polychlorinated Biphenyls
diversity of sources and contaminants in indoor air; (2) other in Air (Withdrawn 2021)
factors that may affect occupant perception and acceptance of D5197 Test Method for Determination of Formaldehyde and
indoor air quality, such as air temperature, humidity, noise, OtherCarbonylCompoundsinAir(ActiveSamplerMeth-
lighting, and psychological stress; (3) the range of susceptibil- odology)
ity in the population. D5438 Practice for Collection of Floor Dust for Chemical
Analysis
1.6 Implementation of procedures given in this standard
D5466 Test Method for Determination of Volatile Organic
requires the investigator (or investigative team) to have ad-
Compounds in Atmospheres (Canister Sampling, Mass
equate background in several areas: general principles of IAQ;
Spectrometry Analysis Methodology)
interviewing techniques; building design and construction
D5952 Guide for the Inspection of Water Systems for
practices; basic understanding of heating and cooling systems
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This practice is under the jurisdiction ofASTM Committee D22 on Air Quality contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
and is the direct responsibility of Subcommittee D22.05 on Indoor Air. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Sept. 1, 2021. Published October 2021. Originally the ASTM website.
approved in 2006. Last previous edition approved in 2014 as D7297 – 14. DOI: The last approved version of this historical standard is referenced on
10.1520/D7297-21. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7297 − 21
Legionella and the Investigation of Possible Outbreaks of USEPA TO-11A Determination of Formaldehyde in Ambi-
Legionellosis (Legionnaires’ Disease or Pontiac Fever) ent Air Using Adsorbent Cartridge Followed by High
D5955 Test Methods for Estimating Contribution of Envi- Performance Liquid Chromatography (HPLC)
ronmental Tobacco Smoke to Respirable Suspended Par- USEPATO-15 Toxic Organics – 15 (TO-15): Determination
ticles Based on UVPM and FPM of Volatile Organic Compounds (VOCs) in Air Collected
D6196 Practice for Choosing Sorbents, Sampling Param- in Specially-Prepared Canisters and Analyzed by Gas
eters and Thermal Desorption Analytical Conditions for Chromatography/Mass Spectrometry (GC/MS)
Monitoring Volatile Organic Chemicals in Air USEPA TO-17 Determination of Volatile Organic Com-
D6271 Test Method for Estimating Contribution of Environ- pounds in Ambient Air Using Active Sampling onto
mental Tobacco Smoke to Respirable Suspended Particles Sorbent Tubes
Based on Solanesol
2.4 Other Documents:
D6333 Practice for Collection of Dislodgeable Pesticide
ANSI/AARSTSGM-SF2017 SoilGasMitigationStandards
Residues from Floors
for Existing Homes
E241 Guide for Limiting Water-Induced Damage to Build-
ANSI/AARST RMS-MF 2018 Radon Mitigation Standards
ings
for Multifamily Buildings
E609 Terminology Relating to Pesticides
ANSI/AARST MAH 2019 Protocol for Conducting Mea-
E620 Practice for Reporting Opinions of Scientific or Tech-
surements of Radon and Radon Decay Products in
nical Experts 6
Homes
E741 Test Method for Determining Air Change in a Single
ANSI/AARST MAMF 2017 Protocol for Conducting Mea-
Zone by Means of a Tracer Gas Dilution
surements of Radon and Radon Decay Products in Mul-
E779 TestMethodforDeterminingAirLeakageRatebyFan
tifamily Buildings
Pressurization
ANSI/AARST MS-QA 2019 Radon Measurement Systems
E943 Terminology Relating to Biological Effects and Envi-
Quality Assurance
ronmental Fate
ANSI/AARST MW-RN 2020 Protocol for the Collection,
E1186 Practices for Air Leakage Site Detection in Building
Transfer and Measurement of Radon in Water
Envelopes and Air Barrier Systems
ANSI/ACCA 4 QM – 2019 Quality Maintenance of Resi-
E1554 Test Methods for Determining Air Leakage of Air
dential HVAC Systems
Distribution Systems by Fan Pressurization
ANSI/ASHRAE 62.2-2019 Ventilation and Acceptable In-
E1827 Test Methods for Determining Airtightness of Build-
door Air Quality in Low-Rise Residential Buildings
ings Using an Orifice Blower Door
E2121 Practice for Installing Radon Mitigation Systems in
3. Terminology
Existing Low-Rise Residential Buildings
3.1 Definitions—For definitions of terms used in this
E2128 Guide for Evaluating Water Leakage of Building
practice, refer to Terminologies D1356, E609, and E943.
Walls
3.2 Definitions of Terms Specific to This Standard:
2.2 ISO Standards:
3.2.1 hypothesis, n—aprovisionaltheorysetforthtoexplain
ISO 16017-2 Indoor, ambient and workplace air — Sam-
certain indoor air quality problems or phenomena.
pling and analysis of volatile organic compounds by
sorbent tube/thermal desorption/capillary gas chromatog-
3.2.2 pause point, n—an interim step within a procedural
raphy — Part 2: Diffusive sampling
sequence designed to allow subsequent actions to be based on
ISO 16000-4 Indoor air — Part 4: Determination of formal-
the analysis and evaluation of recently collected data.
dehyde — Diffusive sampling method
3.2.3 stack effect, n—air movement resulting from air buoy-
2.3 USEPA Documents:
ancy as influenced by differences in air temperature, density or
USEPA 402-F-91-102 Building Air Quality: A Guide for
pressure.
Building Owners and Facility Managers
USEPA 402-K-01-001 Mold Remediation in Schools and
4. Summary of Practice
Commercial Buildings
4.1 IAQ-based complaints and problems in residential
USEPA 600-R-94-173 Technical Notes on Drinking Water
buildingsincludediscomfortandhealthsymptomsarisingfrom
Methods
exposure to indoor air pollutants, as well as adverse indoor
USEPA QA/G-5 EPA Guidance for Quality Assurance Proj-
environmental conditions such as mold or bacterial growth or
ect Plans
persistent odors.
USEPA QA/G-9 Guidance for Data Quality Assessment:
Practical Methods for Data Analysis
Available from American Association of Radon Scientists and Technologists
Available from International Organization for Standardization (ISO), ISO (AARST), Hendersonville, NC, https://standards.aarst.org/.
Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, Available from Air Conditioning Contractors of America (ACCA), 1330
Switzerland, https://www.iso.org. Braddock Place, Suite 350, Alexandria, VA 22314, https://www.acca.org/home.
5 8
AvailablefromUnitedStatesEnvironmentalProtectionAgency(EPA),William Available from American Society of Heating, Refrigerating, and Air-
Jefferson Clinton Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460, Conditioning Engineers, Inc. (ASHRAE), 1791 Tullie Circle, NE, Atlanta, GA
http://www.epa.gov. 30329, http://www.ashrae.org.
D7297 − 21
4.2 This practice describes procedures for the systematic investigator and residents. Examples include but are not
investigation of IAQ concerns using an iterative process that limited to the following:
involves problem definition, information gathering, formula- 6.1.1 Improperly stored or uncharacterized household
tion of hypotheses, measurements (if necessary), and problem chemicals, and pesticides,
source identification. It may include testing hypotheses by 6.1.2 Fire hazards (for example, inappropriate storage of
taking corrective actions and evaluating their impact on the combustible material),
IAQ concern. 6.1.3 Microbiological contamination, and
6.1.4 General safety (for example, weakened staircases).
4.3 To enhance the effectiveness and management of an
IAQ investigation, it is often conducted in three separate 6.2 Many potential hazards are recognized visually, and can
phases: (1) initial meeting(s) with the building owner or be accommodated by asking the homeowner or occupants, as
occupant, or both, and a walk-through, (2) detailed assessment appropriate, to remove the hazards.
of the building and its systems, and (3) pollutant
6.3 If any testing or assessment conducted by the investi-
measurements, if necessary. Such phased investigations also
gator (for example, use of smoke tracers) may impact the
allow informing the building owner or the reporting/impacted
occupants or indoor environment, or both, risks related to such
party of the progress and seeking approval for ensuing work.
procedures must be reviewed with the resident and explicit
However, circumstances may require all three phases to occur
written permission of the resident should be obtained prior to
during a single site visit.
initiating such testing.
4.4 Major steps recommended for IAQ investigations in-
6.4 Where applicable, use protective equipment (for
clude an initial interview with the building owner or occupant,
example, eye protection, gloves, and respirators), and safety
on-site meeting and walk-through, development of hypotheses
procedures (for example, avoid direct inhalation of strong
on potential causes of complaints, determining measurement
vapors) to reduce hazards that cannot be otherwise addressed.
parameters and instrumentation, determining the need and
feasibility of monitoring, if appropriate, conducting
7. Background on the Nature of Residential IAQ
monitoring, analyzing data and evaluating hypotheses, and
Problems, Contaminants and Sources
preparingareportonfindings.Criticalcriteriaunderlyingthese
7.1 For successful diagnosis of IAQ problems, investigators
steps and the procedures involved are described. The relation-
need to have a thorough understanding of types of issues and
ships among the steps are illustrated using a flow diagram.
their potential causes. This section presents background on
4.5 The success of an IAQ investigation often depends on
common types of IAQ problems, contaminants, and indoor
whether the investigator has taken the time to assess all field
sources. This list is not all inclusive. For detailed discussion,
observations and data that have been collected at any given
refer to the documents listed in the bibliography (Annex A7).
point in time to determine or postulate potential causes. These
The next section (Section 8) gives background on building and
interim evaluation points are called pause points and several
system related IAQ problems.
such pause points are recommended during the investigation.
7.2 IAQ Concerns and Problems:
5. Significance and Use
7.2.1 IAQ concerns, issues, and problems may create a
nuisance, discomfort, or health effect. Distinguishing between
5.1 IAQ-based complaints and problems include
these categories can be difficult, especially during the initial
discomfort/medical symptoms and unacceptable indoor envi-
phase of an evaluation.Although some building-related health
ronmental conditions such as odors that exist in residential
effects are clinically diagnosable, many are not. This can blur
buildings. The frequency of the occurrence of IAQ complaints
the distinction between a health effect, nuisance, and discom-
and problems may be unknown.
fort. The investigator’s role is to identify the conditions that
5.2 Characterization of IAQ concerns and identification of
might lead to IAQ concerns and problems; not diagnose health
their underlying causes require systematic observations and
effects.
measurements of the indoor air and environment, its occupants
7.2.2 IAQ concerns, issues, and problems may be perceiv-
and potential contaminant sources. This practice provides
able or imperceivable.Aperceivable concern is one where the
background and procedures for the investigation of IAQ
human senses can identify the problem. Examples include
concerns.
disagreeableodors,moldgrowth,andvisibledepositsofsmoke
5.3 Where the dwelling is not owner-occupied, formal
residues. Imperceivable concerns are not manifested with an
permissiontoaccesscertainareasofthepropertyandtocollect
odor or visual indicator. For example, carbon monoxide and
informationessentialtotheIAQinvestigationisoftenrequired.
radon are colorless and odorless gases that cannot be perceived
by smell or sight. Imperceivable concerns may also arise from
5.4 The stepwise and phased approach described in this
odorant chemicals that are below their odor thresholds, or from
practice allows for an investigation that is commensurate with
too small a visual signal (e.g. mold colony too small to be
the nature of the problem and the level of resources available
observed by the unaided eye). Further, concerns may be
for the investigation.
imperceivable because they are located in inaccessible areas of
6. Hazards and Precautions
the building, such as inside wall cavities or air ducts.
6.1 In the course of conducting on-site investigations, a 7.2.3 IAQ concerns that are based on perceived acceptabil-
variety of situations may arise that could pose a hazard to the ity of environmental conditions include disagreeable odors,
D7297 − 21
visible deposits of soot-like residues, or mold growth on 7.3.3.5 BioeffluentsconsistofCO2producedbyrespiration,
various surfaces, and excessive dust, etc. and a large number of volatile organic compounds (VOCs),
includingcompoundssuchasethanolproducedbymetabolism.
7.3 Contaminants and Indoor Sources:
Individual compounds in lowconcentrations may have a mod-
7.3.1 Twocommontypesofcontaminantsarebiologicaland
est sensory impact, but together may become an unpleasant
chemical contaminants. Biological contaminants represent a
odor or even impact health (4). VOC emissions from mold
broad class of viable particles (viruses, bacteria, protists, and
contamination can also be considered under this category of
fungal spores), and nonviable particles (that is, fragments of
sources. Microbial VOCs (MVOCs) may be present at levels
dead organisms and particulate waste products). Chemical
above odor thresholds.
contaminants can exist as gases, vapors, and aerosols that are
7.3.3.6 In addition to above groups of sources, chemical
ormaybecomeairborne.Therearealsochemicalcontaminants
interaction between chemicals within the same or different
that originate from living organisms.
groups may need to be considered. Examples include interac-
7.3.2 Indoor levels of biologically-derived pollutants may
tion between chlorine compounds in bleach and other chemi-
arise from biological contamination of the indoor environment
cals or interaction between nitrogen oxides or ozone and
(for example, mold colonization), or from the transport of
furnishings.
biologically-derived contaminants from other indoor airspaces,
the outdoors, or from soil gas entry (1, 2).
8. Background on Building and Building Systems-
7.3.3 Sources of chemical contaminants in indoor air can be
Related IAQ Problems
grouped as (1) activity-related, (2) material-related sources, (3)
8.1 IAQ problems may result from elements of the building
transport-related sources, (4) tracked-in dirt, and (5) bioefflu-
itself, the mechanical equipment used to condition and venti-
ents.
late it and interactions between occupants, the building enve-
7.3.3.1 Activity-relatedsourcesarecharacterizedbyprocess
lope and outdoor conditions. Concerns may arise from flaws in
rates. The emission rate for aerosols and gases from combus-
design, construction, operations, or maintenance. This section
tion sources, for example, is often expressed in terms of fuel
provides a brief background on building and system related
consumption rate. Malfunctioning of such sources such as
factors. The discussion below is not comprehensive but illus-
spillage from combustion sources relates to process rate and
trative.
other factors such as depressurization. Other direct-discharge
sources include the use of pressurized consumer products as
8.2 Building Airtightness and Infiltration:
well as volatilization of chemicals from the water supply.
8.2.1 In residences, outdoor air infiltration and mechanical
Activity sources also include tobacco or cannabis smoke,
ventilation are the principal dilution mechanism for pollutants
electronic cigarette and vaping devices, cleaning and bathing
released from indoor sources. The air infiltration amount or air
products, sweeping and vacuuming, cooking, use of home
leakage into a building depends on complex interactions
office equipment, hobbies, painting and varnishing and pest
among variables including but not limited to: indoor-outdoor
control efforts.
pressure differences (which in turn depend on indoor-outdoor
7.3.3.2 Material-related sources include volatilization of
temperaturedifferencesandwindconditions)andtheoperation
chemicals from liquid films (for example, drying paint, clean-
ofexhaustappliancessuchaskitchenorbathroomfans,clothes
ers) and from solid media (for example, carpet backing,
dryers, and fireplaces (5). Window and door openings can add
building materials, glues and paints). Air “fresheners” also
tobuildingairchangerate.Imbalancesintheairdistributionof
generate volatilization of chemicals from solid or liquid media.
a forced-air heating/cooling system caused by barriers between
7.3.3.3 Transport-related sources of indoor air pollution
supply and return or duct leakage contribute further to building
bring contaminated air from other areas into the indoor
depressurization and pressurization. Also, the physical layout
airspace of concern. Examples include infiltration of outdoor
of the building (for example, a flat one-story building “ranch
gasesandaerosols,migrationofcombustionproducts(aerosols
style” versus a taller and narrower structure) influences the
and gases) from attached garages, and soil gas entry. Heating,
stack effect caused by temperature differences and the impact
ventilating, and air-conditioning (HVAC) distribution system
of wind conditions. Such stack effects are increased with
or ductwork can also be a conveyor or source of indoor air
building features such as open stairwells in a multi-floor
pollution.Theimpropermaintenanceormoistureaccumulation
building.
in HVAC system can lead to fungal and bacterial growth. Use
8.2.2 ANSI/ASHRAE 62.2-2019 specifies minimum venti-
of woodstoves and fireplaces can leave residues of polycyclic
lation requirements for providing acceptable air quality in
aromatic hydrocarbons (PAHs) and soot indoors.
residential buildings. Leakage communication between the
7.3.3.4 Tracked-in dirt by individuals, especially children,
buildingandtheoutdoorscanbequalitativelyestablishedusing
or pets coming from outside or a yard to indoors is a common
visual tracers and controlled pressurization and depressuriza-
source of contamination from lawn and garden chemicals such
tion (Practices E1186).
as herbicides, insecticides, fungicides, or fertilizers. Similarly
8.3 Water Leakage and Moisture Damage:
PAHs and other semivolatile organics can come from nearby
8.3.1 Unwanted water penetration into exterior walls, inte-
roadways, restaurants, industrial sites, and landfills (3).
rior walls, and floors causes direct water damage to such
components and areas as well as secondary damage including
that resulting from mold growth. (An exterior wall system
The boldface numbers in parentheses refer to the list of references at the end of
this standard. includes exterior and interior finishes, fenestration, structural
D7297 − 21
components and structural components and perimeter units proper performance, as malfunctioning may result in unabated
associated with heating, cooling, and ventilation.) Water pen- intrusion of soil gas into indoor spaces.
etration or leakage is considered problematic if it exceeds the
8.7 Potable Water Supply:
planned resistance, or temporary retention and drainage capac-
8.7.1 Residential water supplies may contain chemicals to
ity is causing premature deterioration of a building or its
which occupants can be exposed through ingestion, dermal
contents or is adversely affecting the performance of other
contact, or inhalation (10).
components (Guide E2128). Plumbing leaks and condensation
8.7.2 Chemicals and gases conveyed to the indoor environ-
can result in extensive fungal growth.
ment by the water supply include contaminants subject to
volatilization during water use (for example, trichloroethylene)
8.4 Heating/Cooling Systems:
or aeration of water (for example, radon). Water delivered by
8.4.1 Central forced-air residential heating and cooling
municipal systems may contain disinfection by-products such
systems installed in dwellings are designed to recirculate air.
as chloroform that are produced in the course of water
The number of dwellings that are served by central HVAC
disinfection processes (11). Domestic well water contamina-
systems designed to bring in outdoor air are limited, in the
tion may be caused by industrial activities (for example,
U.S.A. but are becoming more common. However, such
hazardous waste disposal) as well as naturally occurring
systems when present may be equipped with air-to-air heat
processes (for example, arsenic) (11).
exchangers for energy conservation.
8.7.3 Among indoor water uses, showering, bathing and
8.4.2 Humidification—Humidification systems may be inte-
hand washing of dishes or clothes provide the primary oppor-
gral to the central forced-air heating system, or may appear in
tunities for dermal exposure (10, 11).
the form of portable (room-sized) units. Humidification sys-
8.7.4 The inhalation exposure potential for a given water
tems are designed to inject water vapor into indoor air and,
usescenariodependsonthewatersource,thetypesandextents
depending on details of design and maintenance, can become
of water uses, and the extent of volatilization of specific
reservoirs for mold and bacteria.
chemicals. Such inhalation exposure can occur during various
8.5 Intake and Exhaust Fans:
types of residential water use including showering, bathing,
8.5.1 Local exhaust fans remove unwanted odors and other
toilet use, clothes washing, dishwashing, and faucet use (11,
contaminates from specific areas such as kitchens and bath-
12).
rooms and, in some cases, areas set-aside for specific hobbies
8.8 Sanitary Drains:
(for example, woodworking, ceramics). Note that many
8.8.1 Sewer gases have been of concern for the indoor
kitchen range hoods do not exhaust air directly to the outdoors.
environment since the inception of indoor plumbing (13).In
Rather, cooking emissions are recirculated through a grease
modern buildings, sanitary drains can become conduits for
trap/filter housed in the range hood.
sewergasifwaterinthedraintrapevaporatesduetoinfrequent
8.5.2 Ventstacksassociatedwithlocalexhaustfan(s)should
use. If the building interior is under negative pressure, sewer
be located to avoid re-entrainment of vented material, and the
gas can be drawn indoors through the dry drain trap or in the
extraction efficiency of the exhaust fan(s) should be optimized
event of sewer line leaks outside the building may be drawn in
by selecting proper flow capacity so that these fans do not
as part of the soil gas.
depressurize the building. Building depressurization can inter-
fere with venting of combustion appliances and allow combus-
9. Overall Strategy and Steps in IAQ Investigations
tion products to spill into the interior space.
9.1 Conceptually, the investigation of IAQ concerns is an
8.5.3 Whole-house fans, operating via thermostat or user
iterative process that involves gathering information, formula-
control, can significantly depressurize the building during
tion and testing of hypotheses, problem identification, and
operation.
problem resolution (Fig. 1). (As stated in section 1.4, problem
8.6 Soil Gas Transport:
resolution is not within the scope of this document and thus is
8.6.1 The pressure imbalances that drive infiltration/ shown in a dotted line box in Fig. 1; although the IAQ
exfiltration also control contaminant entry via soil-gas trans- investigator can provide recommendations for possible solu-
port through building surfaces in contact with soil (6, 7, 8). tions and, if necessary, interim measures for temporary relief.)
8.6.2 Most scientific studies of soil-gas entry are associated
9.2 The IAQ investigation is the principal means of gather-
with indoor radon (6, 8). Even in areas judged to be of low
ing information on IAQ concerns (symptoms and complaints
radon potential, however, significant IAQ problems can prevail
elicited through interviews and observation) and information
from VOCs and other gas phase contaminants present in the
relating to potential causes (as observed or based on measure-
surrounding soil (7).
ments conducted by the IAQ Investigator).
8.6.3 While basements are designed to provide some resis-
9.2.1 Information on IAQ problems and potential sources
tance to soil-gas entry, numerous pathways exist in the form
canbeobtainedinvariousways: (1)fromtheoccupantthrough
designedjointsaswellascracksthatforminconcrete.Soil-gas
interviews, (2) on-site observations by the IAQ Investigator(s),
can also diffuse through intact concrete, though at a much
(3) discussion with management and maintenance personnel
slower rate than with pressure-driven flow (6, 8, 9).
(for tenant-occupied premises) and (4) on-site testing/
8.6.4 The radon subslab depressurization system used in monitoring. The concept of testing and monitoring includes
high soil gas areas should be tested to ensure to ensure its medical evaluation as well as environmental monitoring. To
D7297 − 21
FIG. 1 Iterative Approach to Solving IAQ Problems
diagnose a health problem, medical evaluations are conducted extensive understanding of factors affecting indoor air quality
by physicians or other health professionals to assess the andunderstandingofthepracticalrealitiesofbuildingsystems.
residents’ symptoms, observations by the health professional,
9.3.1 Hypothesis testing is a useful design tool for data
and results of the clinical tests. Environmental monitoring is
interpretation, such as comparing and assessing the magnitude
conducted by the IAQ Investigator to measure air concentra-
of measured values compared to criteria. Traditional hypoth-
tions of selected contaminants.
esis testing is a procedure for deciding whether to accept or
9.2.2 Reports of allegations of building-related illness may
reject a statement. The full statement of the statistical hypoth-
require a physician’s diagnosis and assessment of potential
esis has three major parts: the hypothesis being tested, a null
exposures. Such medical evaluations may involve health pro-
hypothesis (that is, the statement to be accepted or rejected),
fessionals interviewing concerned individuals, compiling de-
and an occasional alternative hypothesis (that is, the statement
tailed medical histories and conducting physical examinations
to be accepted if the null hypothesis is rejected). In all parts, a
and tests.
population parameter is compared to either a fixed value or
9.2.3 Adequate information from both areas—IAQ con-
another population parameter. The population parameter is a
cerns and potential sources—is necessary for the formulation
quantitative characteristic of the population that the investiga-
of a hypotheses on potential causes for complaints and for
tor wants to estimate using the data, such as the mean value.
subsequent testing of each hypothesis to accept or reject each
Considering that IAQ investigations are not research projects,
provisional theory of causes for complaints. While hypothesis
it is not possible to recommend that the project adhere to
testing leads to problem identification, more than one iteration
statistical hypothesis testing. However, the concepts underly-
of hypothesis development and testing may be required, and
more than one problem may be identified. ing the development of hypothesis and testing provides a good
platform for refining the investigative thought process on an
9.3 Development and testing of hypotheses is probably the
on-going investigation.
most challenging part of the IAQ investigation. It requires
D7297 − 21
9.3.2 For residential IAQ complaints and issues, developing 9.4.2 Phase II—The purpose of this phase is to conduct a
and evaluating hypotheses involves review and analysis of detailed assessment of various possible problem sources such
information from various sources, steps, or phases of the
as water leakage and systems such as heating/cooling appli-
investigation. In particular, it involves control experiments ancesandforced-airdistribution.Someoftheaspectssurveyed
such that the impact of suspected sources and contributing
in Phase I may need to be repeated to obtain detailed
factors could be identified.
understanding of the building and its systems. Also, certain
on-site evaluations such as pressure mapping are conducted to
9.4 TheIAQinvestigationisconductedindiscretephasesto
provide insights into potential problems. IAQ problems are
enhance the effectiveness and management of the investiga-
often identified in this phase. If they are not identified, plans
tion. Such phased investigations provide for informing the
aredevelopedtoeithercontinuefurtherPhaseIIevaluationsor,
building owner or the impacted party of progress and provides
as necessary, develop hypothesis and plans for contaminant
for obtaining additional approvals, including that of budget
measurements (Phase III). The resources required for Phase III
approvals, for continuing work. IAQ investigations are often
are estimated for obtaining necessary approvals.
conducted according to the following phases:
9.4.3 Phase III—Contaminant measurements may aid in
9.4.1 Phase I—Conduct an on-site interview followed by a
walk-through of the building and its surrounding. The purpose identification or confirmation of IAQ problem. Systematic
of this phase is to understand the problem and identify, to the development of measurement and data quality objectives is
extent feasible, potential causes. Developing plans for the next veryimportantpartbeforeperformingPhaseIIImeasurements.
phase (Phase II), estimating required resources, and obtaining The results sometimes indicate the need for repeating Phase III
approval for performing Phase II are part of this effort. or even Phase II.
FIG. 2 An Illustrative Flow Diagram for IAQ Investigations
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9.4.4 Fig. 2 provides a flow diagram for the three investi- 9.4.6 Additionally, while the steps stated above and de-
gative phases and emphasizes the iterative process involved in scribed in this practice are focused on IAQ investigations,
anIAQinvestigation.Thefollowingstepsthatareapplicableto theseproceduresmayprovideastandardizedbasisforconduct-
one or more phases are shown in the figure: ing IAQ research.
9.4.4.1 Conduct initial interview,
9.5 Understand Critical Purposes Underlying Major Steps
9.4.4.2 Conduct on-site meeting,
in the Process for Evaluating Residential IAQ Concerns:
9.4.4.3 Identify walk-through areas of emphasis,
9.5.1 AlthoughIAQinvestigationsdescribedinthispractice
9.4.4.4 Conduct walk-through exterior survey,
for identifying the source(s) of the problem may give the
9.4.4.5 Conduct walk-through interior survey,
appearance of being a set of simple or straightforward steps,
9.4.4.6 Conduct post-walk-through interview,
this can be misleading and successful investigations can be
9.4.4.7 Develop hypotheses,
very challenging. Thus, to carry out investigations and achieve
9.4.4.8 Determine measurement parameters and
reliable outcomes, it is essential that investigators understand
instrumentation,
the objectives for each major step.
9.4.4.9 Make decision regarding monitoring,
9.5.2 The major steps in the evaluation process outlined
9.4.4.10 Conduct monitoring,
abovearelistedinTable1.TheintentofTable1istoemphasize
9.4.4.11 Analyze data and evaluate hypotheses,
objectives underlying each step in the investigation.
9.4.4.12 Quality assurance, and
9.5.3 The success of an IAQ investigation often depends on
9.4.4.13 Report findings.
whether the investigator has stepped back to assess all field
9.4.5 Note that while data analysis and hypotheses evalua-
observations and collected data to determine causes or postu-
tion is described in a separate section near the conclusion of
late potential causes.
this standard, in actual practice, the analysis of observations
9.5.4 These evaluation points are called pause points and
and data, evaluation of hypothesis, and their interpretation is a
five such pause points are recommended during the investiga-
continuous process associated with all steps and sub steps of
tive process. Table 2 lists these pause points and the type of
the investigation. It should also be noted that the phases may
information, observations, and results to be evaluated.
notalwaysbeclearlydelineatedandcouldbeintermingled.For
example, combining some characterization measurements with
10. Conduct Initial Interview of Residents
inspection and hypothesis testing with detailed inspection may
be necessary to limit the number of site visits. In any case, the 10.1 The initial interview is generally conducted by tele-
phasing principle is very important in conducting successful phone.Theinterviewshouldincludequestionsinthefollowing
investigations and, thus, any deviation from phasing as de- areas: dwelling information; nature and the history of the
scribed in this document is acceptable as long as the concept problem; resident information; and contact and address infor-
itself is not compromised. mation. Since the interview is conducted by telephone, the
TABLE 1 Critical Purposes Underlying Various Steps in the Approach for Evaluating Residential Indoor Air Quality Problems
Section Step Underlying Critical Purpose
10 Conduct initial interview To obtain basic information about the complaint, the dwelling, and residents and
to confirm the likely existence of an IAQ problem.
11 Conduct on-site meeting To gain confidence of the residents, and to get their first-hand impressions of
the problem, including perceived potential causes.
11.4 Develop plans for walk-through Pause to focus attention on elements of walk-through based on a best
understanding of the perceptions of the problem, its history and its impact on
the residents.
11.5 Conduct exterior walk-through survey To review immediate and nearby surroundings to examine if any exterior factors
may contribute to the IAQ problem under investigation.
11.6, 11.7 Conduct interior walk-through survey To review in a comprehensive manner the building envelope, HVAC, appliances,
furnishings, drains, water supply, etc., to judge their impact on IAQ and role in
the IAQ problem under investigation. Review related information.
11.8 Conduct post walk-through interview To gain insights into the resident practices that may have an impact on IAQ and
a role in the IAQ problem under investigation.
12 Develop hypotheses Pause to assemble all information collected thus far into a systems perspective
to track IAQ problems back to possible origin(s) and to develop a specific
statement of the problem.
13.2 Determine measurement parameters and instrumentation To select instrumentation for hypotheses evaluation.
13.3 Decisions Regarding Monitoring Pause to evaluate whether to conduct measurements based a review of how
measurements will help in hypothesis evaluation and the investigation in
general. If affirmative, establish criteria and objectives for measurement.
13.4 Conduct monitoring To obtain primary data and test the hypotheses.
14 Analyze data and Evaluate hypotheses To analyze data for testing hypotheses.To accept or reject hypotheses based on
the collected data. Based on the outcome either to identify causes of the IAQ
problem or to construct a new hypotheses for testing and returning to Section
12 activity.
16 Maintain Quality Assurance To ensure that defined quality standards are met; a quality assurance plan
should be in force prior to conducting field operations.
17 Report Findings To develop the report in a manner that is appropriate for court proceedings, if
needed, and to share with the resident details of the investigation and results.
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TABLE 2 Pause Points and Problem Assessment
Stages in Problem Assessment: The Type of Information,
No. Pause Points
Observations, and Results to be Evaluated
1 After initial on-site visit and interview Summarize the problem(s); potential areas to be investigated; plans for walk-
through.
2 After walk-through (Phase I) and before proceeding to Problem observations; identification, if any at this stage, of potential causes.
building and systems characterization Proposal for building/systems characterization.
3 After building/system characterization (Phase II) Identification, if any at this stage, of potential complaint causes. Rationale,
strategy, measurement plan including criteria, and resources for proposed
monitoring under Phase III.
4 After completion of Phase III investigation and Measurement results and comparison with criteria and objectives. Conclusions
measurements and analysis drawn from measurements.
5 After an overall and final evaluation of the problem Nature of problem(s) discovered, relationship of the problem(s) to the symptoms
and complaints, qualitative degree of confidence in such relationships.
questionnaire scope must be constrained to accomplish prepared questionnaires enable data collection in an organized
information-gathering without unduly burdening the respon- format,anyquestionandanswersessionswithresidentsshould
dent. Note that experience has shown that fairly detailed be open-ended so that all information relevant to an investiga-
telephone questionnaires can be administered to gather infor- tion is collected.
mationrelatingtoresidentialIAQintimeperiodsthatconsume
no more than 15 to 20 minutes of respondent time (14).
11. Conduct On-Site Investigation
10.2 The initial interview should collect information on the
11.1 The on-site investigation should be composed of the
following:
following: (1) initial on-site meeting, (2) walk-through, and (3)
10.2.1 The type of building, year of construction and
detailed interview(s). This sequence is important because the
remodeling if any, number of bedrooms, and type of major
IAQ investigator needs to engage the resident(s) in the defini-
appliances(cooking,waterheating,spaceheatingandcooling).
tion and resolution of the problem and maintain that interest
10.2.2 Household characteristics, including number of
throughout the on-site investigation. This sequence also assists
persons, ages of children and adults, and particular health
in gaining the confidence of the household members. This is
problems experienced by each person.
necessary for acquiring answers to potentially sensitive follow
10.2.3 The nature and history of the problem as perceived
up questions relating to factors such as personal habits,
by the resident(s), including any activities or environmental
hygiene, and possible culpability during the detailed resident
changes that may coincide with the IAQ concern, and any
interview.
medical evaluations.
11.2 Support equipment and field supplies necessary to
10.2.4 Possible outdoor sources suggested by the resident,
conduct the On-Site Investigation include field data collection
such as nearby streets and street intersections, airports, and
forms, a camera, a flashlight, small hand tools like
commercial/industrial facilities.
screwdrivers, and a stepladder. Also as detailed later, a few
10.2.5 Other IAQ problem cases and unaffected (that is,
IAQinvestigationtoolssuchasasmokebottle,moisturemeter,
control) residences in the neighborhood as practical. (The
and temperature gauge can provide useful information during
information on other cases and use of controls is useful if the
the walk-through without consuming substantial time or re-
initialiterationofon-siteinvestigationfailstoproduceresults.)
sources.
10.3 The initial telephone interview should request or con-
11.3 Conduct Initial On-Site Meeting:
firm address and contact information to facilitate subsequent
11.3.1 The initial meeting sets the overall tone for coopera-
on-site activities.
tionandinquisitivenessfortheon-siteinvestigation.Thisgains
10.4 The scope of work, including permission to perform a
the confidence of the resident and facilitates acquisition of the
walk-through, should be discussed and agreed upon prior to
best available information by the IAQ Investigator. The initial
arriving on site. The investigator should ask if there are any
meeting also allows the IAQ Investigator to probe into the
areas to be avoided or excluded during the walkthrough. If
nature and the history of the problem beyond the initial
there are such areas, the resident/owner shall be informed that
interview of the resident.
this may impact the IAQ investigation, and limit the identifi-
11.3.2 Gather the following information during the initial
cation of sources or causes of IAQ problems.
meeting: when the problem was first noted, continuous or
10.5 An example questionnaire suitable for use in an initial intermittent nature of the problem, frequency of occurrence,
telephone interview is given in Annex A1. Note, this Annex suspected causes, details on any prior investigations and their
and other Annexes provide example questionnaires. Before results,andanyremediationstepsundertaken.Whilecollecting
initiating an investigation, these examples should be rev
...