ASTM D7338-14(2023)

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: D7338 − 14 (Reapproved 2023)
Standard Guide for
Assessment Of Fungal Growth in Buildings
This standard is issued under the fixed designation D7338; 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 1.8 Recommendations for remediation of fungal growth are
beyond the scope of this guide.
1.1 This guide provides a compendium of information and a
menu of options for assessment of fungal growth in buildings, 1.9 This guide is not intended to supersede any government
but does not recommend a specific course of action. Due to the regulations governing the assessment of fungal growth in
wide variety of fungal problems affecting buildings and their buildings.
occupants, and the wide variety of buildings, it is not possible
1.10 This standard does not purport to address all of the
to describe a set of uniform steps that will always be performed
safety concerns, if any, associated with its use. It is the
during an assessment (that is, a standard practice); therefore the
responsibility of the user of this standard to establish appro-
user of this guide must decide which steps are appropriate for
priate safety, health, and environmental practices and deter-
a given situation or building.
mine the applicability of regulatory limitations prior to use.
1.11 This international standard was developed in accor-
1.2 This guide is specific to fungal growth, which is only
dance with internationally recognized principles on standard-
one potential problem in a building environment. It may be part
ization established in the Decision on Principles for the
of, but is not intended to take the place of, a comprehensive
Development of International Standards, Guides and Recom-
indoor air quality investigation.
mendations issued by the World Trade Organization Technical
1.3 This guide describes minimum steps and procedures for
Barriers to Trade (TBT) Committee.
collecting background information on a building in question,
procedures for evaluating the potential for moisture infiltration
2. Referenced Documents
or collection, procedures for inspection for suspect fungal
2.1 ASTM Standards:
growth, and procedures beyond the scope of a basic survey that
C755 Practice for Selection of Water Vapor Retarders for
may be useful for specific problems.
Thermal Insulation
1.4 Assessments for fungal growth may be useful wherever
C1699 Test Method for Moisture Retention Curves of Po-
fungal growth is suspected, excess moisture has been present
rous Building Materials Using Pressure Plates
or when there are concerns regarding potential fungal growth.
D653 Terminology Relating to Soil, Rock, and Contained
1.5 Periodic fungal assessment in buildings may be a
Fluids
component of preventative maintenance programs.
D4442 Test Methods for Direct Moisture Content Measure-
ment of Wood and Wood-Based Materials
1.6 This guide is applicable to buildings including residen-
E331 Test Method for Water Penetration of Exterior
tial (for example, single or multi-family), institutional (for
Windows, Skylights, Doors, and Curtain Walls by Uni-
example, schools, hospitals), government, public assembly,
form Static Air Pressure Difference
commercial (for example, office, retail), and industrial facili-
E547 Test Method for Water Penetration of Exterior
ties.
Windows, Skylights, Doors, and Curtain Walls by Cyclic
1.7 Recommendations for developing a sampling strategy or
Static Air Pressure Difference
methods for the collection and analysis of fungal samples are
E631 Terminology of Building Constructions
beyond the scope of this guide. For recommendations for
E1105 Test Method for Field Determination of Water Pen-
developing a sampling strategy, see Ref (1) , Chapter 10.
etration of Installed Exterior Windows, Skylights, Doors,
and Curtain Walls, by Uniform or Cyclic Static Air
This guide is under the jurisdiction of ASTM Committee D22 on Air Quality
Pressure Difference
and is the direct responsibility of Subcommittee D22.08 on Assessment, Sampling,
and Analysis of Microorganisms.
Current edition approved Jan. 1, 2023. Published February 2023. Originally
approved in 2010. Last previous edition approved in 2014 as D7338 – 14. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
DOI:10.1520/D7338-14R23. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
The boldface numbers in parentheses refer to a list of references at the end of Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7338 − 14 (2023)
E1186 Practices for Air Leakage Site Detection in Building ‘mildew’ are frequently used by laypersons when referring to
Envelopes and Air Barrier Systems various fungal colonization.
E1356 Test Method for Assignment of the Glass Transition
3.2.5 fungal spore, n—general term for a reproductive
Temperatures by Differential Scanning Calorimetry
structure in fungi. The spore is the structure that may be used
E2128 Guide for Evaluating Water Leakage of Building
for dissemination and reproduction, and may be resistant to
Walls
adverse environmental conditions.
E2270 Practice for Periodic Inspection of Building Facades
3.2.6 hypha, n—(pl. hyphae) tubular filament of fungal
for Unsafe Conditions
cells; the basic vegetative structure of the body of fungi
2.2 Non-ASTM Standards:
(excluding yeasts).
ANSI/GEI Standard MMS1001 Mold and Moisture Man-
3.2.7 fungal growth, n—vegetative portion of a fungus.
agement Standard for New Construction
3.2.8 infrared thermography, n—thermal imaging, also
called thermography, is the production of non-contact infrared,
3. Terminology
or “heat” pictures from which temperature measurements can
3.1 Definitions:
be made.
3.1.1 building envelope, n—the outer elements of a
3.2.9 remediation, n—to correct a problem. Related to
building, both above and below ground, which divide the
fungal contamination, remediation includes correcting the
external from the internal environments. Commonly included
water and moisture problems and the cleaning, removal, and/or
are exterior walls, windows, doors, roofs and subfloors. E631
replacement of mold-damaged or -contaminated materials.
3.1.2 bulk sample, n—piece or quantity of bulk material that
3.2.10 thermal bridging, n—a phenomenon that occurs
has been selected by some sampling process. D653
when heat is transferred at a substantially higher rate through
3.1.3 capillary action, n—(or capillary migration), of water,
a component, or assembly of components in a building
movement of water induced by the force of molecular attrac-
envelope, than through the surrounding envelope area.
tion (surface tension) between the water and the material it
contacts. E631
4. Summary of Guide
3.1.4 condensation, n—the process of converting a material
4.1 This guide presents a framework for locating and
in the gaseous phase to a liquid by decreasing temperature or
evaluating suspect fungal growth in buildings. Topics include
by increasing pressure, or both. E1356
background information, a basic assessment strategy and
3.1.5 exposure, n—contact with a chemical, biological,
additional or advanced procedures.
physical, or other agent over a specified time period. E1356
4.2 Components of a basic assessment strategy may include
3.1.6 moisture content, n—mass of water retained in the
(1) defining a scope of work, (2) collecting background
specimen divided by the dry mass of the specimen. C1699
information on the building and building systems, (3) formu-
3.1.7 soot, n—agglomerations of particles of carbon impreg-
lation of a hypothesis or hypotheses, (4) an on-site survey for
nated with tar, formed in the incomplete combustion of
fungi, moisture dynamics, and heating. ventilating and air
carbonaceous material. E1356
conditioning (HVAC) operation, and (5) documentation and
3.1.8 vapor retarder, n—a material or system that ad- reporting. Every component of the basic assessment shown
equately impedes the transmission of water vapor under below may be considered optional, since even some of the
specified conditions. E631 most basic steps may not be needed for certain well-defined
situations.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 boroscope, n—device for internal inspection of diffi- 4.3 When the information from the basic assessment is
cult access locations such as wall cavities. Its long narrow tube
insufficient to support decision-making, additional procedures
contains a telescope system with a number of relay lenses. for a follow-up study may include: (1) characterizing site
Light is provided via the optical path or fiber bundles. moisture in greater detail to assist in locating suspect fungal
growth and controlling excess moisture; (2) accessing surfaces
3.2.2 effloresce, v—process by which water leaches soluble
likely to harbor hidden fungal growth; and/or (3) sampling if
salts out of concrete or mortar for surface deposit. Also
necessary to test a specific hypothesis.
efflorescence, n, the name for these deposits.
3.2.3 enzyme activity, n—measure of the quantity of active
5. Significance and Use
enzyme present. Enzyme activity is essential to metabolism.
5.1 This guide presents options for a systematic assessment
Specifically, beta-N-acetylhexosaminidase (NAHA) is an en-
of fungal growth in buildings.
zyme present in all filamentous fungi, the measurement of
which has been shown to be directly proportional to the amount
5.2 This guide allows for site-specific flexibility and profes-
of fungal biomass (see (2, 3).
sional judgment in the choice of assessment procedures. It may
3.2.4 fungus (s), fungi (pl.), n—eukaryotic, heterotrophic, not be necessary to perform in its entirety the basic assessment
absorptive organisms that usually develop a rather diffuse, presented below to resolve a particular problem, for example,
branched, tubular body (that is, network of hyphae) and usually where fungal growth is localized and the source and extent of
reproduce by means of spores (4). The terms ‘mold’ and moisture is readily observable.
D7338 − 14 (2023)
5.3 Conversely, no matter how comprehensive the survey, 6.2.1.4 Sustained elevated humidity;
all fungal growth may not be identified or located in a fungal 6.2.1.5 Wicking due to capillary action from wet material.
assessment.
6.2.2 Whether or not fungal growth actually occurs is
dependent on:
5.4 Material removal or destructive investigation may be
6.2.2.1 Substrate porosity (for example, materials such as
needed to access suspect surfaces.
carpet tack strip and conventional drywall are highly
5.5 Using the procedures described in this guide, the inves-
susceptible),
tigator may have obtained the data necessary to suggest
6.2.2.2 Moisture resistance (for example, some drywall,
specific recommendations, for example, how to remediate the
gypsum plaster and sheathing products are modified to resist
observed fungal growth, or how to prevent further fungal
moisture or to limit water storage and/or are treated with an
growth, but those recommendations are beyond the scope of
anti-microbial agent),
this guide.
6.2.2.3 Moisture duration (for example, leaks which are
5.6 Precautions may be needed to protect the assessor and
single events or intermittent may dry before fungal growth is
building occupants where access may disturb fungal growth. initiated; elevated humidity typically does not trigger fungal
growth unless it is sustained),
5.7 It is the user’s responsibility to protect information that
6.2.2.4 Air circulation and dehumidification (for example,
may be considered confidential, or private, or both, in accor-
moisture may remained trapped when sealed behind
dance with project contract, corporate protocol, or local, state,
baseboards, attached furniture or vapor barriers).
and federal regulations, or a combination thereof.
6.3 Detection of Fungal Growth:
5.8 It may be necessary to enlist other disciplines or trade
6.3.1 Fungus grows on an appropriate substrate. Fungal
expertise to assist in some steps of the assessment, but
growth is associated with biodegradable building materials (for
recommendations of when to enlist and whom to enlist are
example, paper covered gypsum wallboard, wood, ceiling
beyond the scope of this guide.
tiles). It will not grow on inorganic materials (for example,
masonry, concrete, gypsum plaster, stone, glass, ceramic tiles,
6. Background Information
grout) except where dust, dirt, grease or oil is present. It
6.1 Fungal Biology:
usually appears on surfaces which are wet or were previously
6.1.1 Fungal Growth—Fungi constitute over 25 % of the
wet. Fungal growth may pre-exist on wood surfaces not subject
earth’s biomass and are naturally present in every indoor and
to water damage on-site. For example, wood used for building
outdoor environment. Fungal spores (small propagules emitted
materials often becomes stained during tree growth or milling
from surface growth) are ubiquitous in air and settled dust.
6.3.2 Fungal growth may be detected by simple visual
Fungal growth requires sufficient available moisture that is
inspection. Fungal growth may appear as raised, powdery
sustained for a sufficient time, a suitable food source/substrate,
deposits, rings or colored spots which may be black, gray,
and a favorable range of temperature and pH. Both active and
white, green, red, resembling cotton, velvet, leather, or powder.
inactive (past) growth are termed “colonization” (5, 6, 7).
When rubbed, dried fungal growth tends to spread or smear as
Fungi can become dormant only to resume growth again in
a powder.
response to changing environmental conditions (for example,
6.3.3 Discoloration is not necessarily fungal growth. The
during periodic moisture intrusions).
following surface markings should not be categorized as
6.1.2 Fungal Spore Production—Fungal spores are pro-
suspect fungal growth: yellow/brown water stains, scuffs, soot,
duced during active growth, but may be released into the air
dye, dust, ghosting (dust deposits form an outline on a cool
either during active growth or dormancy. Where fungal growth
surface), efflorescence, adhesives, and other residues of
is located behind a wall, wall covering, ceiling, or carpet,
occupancy, maintenance, or construction.
spores may, but are less likely to reach the occupied space
6.3.4 Visual detection of fungal growth is not always defini-
through this physical barrier (the potential for infiltration
tive. Where the origin of discoloration or staining is not clearly
depends on pressure differentials, filtration, occupant activities,
fungal or non-fungal to the investigator, the discoloration
barrier openings and other pathways, etc.) (8, 9, 10, 3).
should be considered suspect fungal growth. In some cases, an
6.1.3 Fungal Variation—Types and concentrations of air-
ambiguous appearance may be resolved by comparing the
borne or surface fungal spores at a given site as well as
suspect surface with the same material which has not been
colonization vary substantially as they are influenced by many
subjected to wetting to determine if the suspect color or texture
natural and manmade factors. Because of this variability,
was pre-existing. If essential to the assessment conclusions, the
testing based on a limited number of samples may not be
discoloration may be confirmed (see below).
representative (6, 7).
6.3.5 Visual detection of fungal growth may not always be
6.2 Fungal Growth in a Building:
possible even when exposed. Very early stages of fungal growth
6.2.1 Indoor fungal growth is generally observed on sur- may not be visible to the unaided eye. Visual detection of
faces subject to one or more of these conditions:
fungal growth may be difficult where substrate color is similar
6.2.1.1 Condensation; (for example, black on black) or where discoloration is covered
6.2.1.2 Spills, leaks or floods; by dust or debris.
6.2.1.3 Consistent wetting, such as from landscape sprin- 6.3.6 Fungal growth may be inaccessible or hidden. Many
klers; surfaces in a building cannot be examined without considerable
D7338 − 14 (2023)
damage, for example, the back or inside of wall cavities or cavities may result in leaks including: (1) roof leaks, (2)
plumbing chases. It is axiomatic that fungal growth cannot be window leaks, and (3) façade leaks (E2128, E331, E2270).
visually detected on a surface that was not examined. Nearby
6.4.2.3 Wind-Driven—Where the above sources of moisture
fungal growth may be hypothesized if surface deposits are are wind-driven, damage may tend to concentrate on one side
found to be consistent with settled material generated by fungal
of the building or at different heights (E2128).
growth. In such a case, destructive examination may have to be
6.4.2.4 Humidity-Related—Fungal growth may occur when
added to the scope of work in order to find the fungal growth
humidity is elevated over an extended period of time when: (1)
in situ.
there is excessive natural ventilation with humid air (for
6.3.7 Visually suspect fungal growth may be confirmed.
example, through open windows, structural penetrations, or
Microscopical examination, culture or biochemical analysis crawlspace vents); (2) there is localized high humidity pro-
(for example, enzyme activity-NAHA or ergosterol) can be moted by lack of air circulation; (3) there is condensation of
used to confirm the presence of fungal material or fungal humid air on cooled surfaces (for example, wall cavities may
growth. Analytical findings of the presence of spores alone do contain condensed moisture from outside in a hot climate or
not demonstrate growth because of the ubiquitous presence of from inside in a cool climate which reaches its dew point on an
spores in settled dust. Analytical methods differ in their ability assembly which supports fungal growth), (4) there is thermal
to accurately identify fungal types (6, 7, 11, 12, 3, 13). bridging such as exterior walls by the floor; and (5) there is
moisture movement from crawlspace soil that is not covered by
6.4 Building Moisture:
an adequate vapor retarder (C755, (5, 14); and see also
6.4.1 Moisture Characteristics—An understanding of build-
HVAC-Related).
ing moisture is generally necessary to help identify the
6.4.2.5 Occupancy-Related—Activities of the building oc-
underlying cause of fungal growth and estimate the extent.
cupants may impact moisture levels as follows: (1) laundry (for
When evaluating moisture dynamics in a facility, the following
example, unvented clothes dryer), (2) failure to operate exhaust
potential pathways should be considered (14):
in shower, bath or cooking area, (3) cleaning (for example,
6.4.1.1 Rain leakage through the building envelope may
excess water use or inadequate drying), (4) potted plants (for
involve simple penetration or be wind-driven. Leak points
example, over-watering), (5) spills or overflows (for example,
often occur at borders between materials (for example,
sink, tub), (6) wet contents (for example, damp laundry), (7)
damage, gaps, deficient flashing), which are generally visible
pools, spas or other water features, (8) fire suppression, and (9)
to the naked eye.
maintenance (for example, failure to promptly resolve
6.4.1.2 Brick and concrete block are porous, affording a
moisture-related incidents).
potential pathway for moisture in buildings.
6.4.2.6 Plumbing-Related—Mechanical systems commonly
6.4.1.3 Water flows to lower elevations by gravity.
contribute to fungal growth as follows: (1) pipe leaks, (2) drain
6.4.1.4 Water may rise against gravity (wick) through a
backups, and (3) pipe condensation (for example, insulation
porous material by capillary action.
deficiencies).
6.4.1.5 Air infiltration containing water in a gaseous phase
6.4.2.7 Drainage-Related—Water originating adjacent to or
occurs.
under the building may be significant when the following
6.4.1.6 Water vapor migrates to areas of lower air or vapor
occur: (1) flooding from excessive rainfall or snow melt, (2)
pressurization (for example, may be driven by molecular high water table, (3) inadequate drainage control, (4) moisture
diffusion, mechanical system or wind).
wicks through foundation causing basement dampness, (5)
sump pump failure, and (6) blocked French drain (14).
6.4.1.7 Evaporation of standing water may increase airborne
moisture available to fungi. 6.4.2.8 HVAC-Related—Design, operation, and mainte-
nance of building systems may impact moisture levels as
6.4.1.8 Water leakage may remain hidden within wall,
follows: (1) inadequate condensate drainage (for example,
ceiling or floor systems.
drain pan overflows due to blockage); (2) moisture carries over
6.4.2 Common Moisture Problems (A lack of moisture
beyond coils; (3) excessive humidification; (4) system fails to
balance between wetting and drying of building assemblies):
provide adequate humidity control due to design, malfunction,
6.4.2.1 Construction-Related—During the construction
or unrepresentative controls or sensor location (for example, if
process, the following situations may contribute to fungal
the outside air exceeds capacity of the system to dehumidify, or
growth: (1) stockpiled materials which are open to the
if the outdoor air damper remains open to allow continual
elements, (2) products installed with excessive moisture, (3)
humid air influx, or if oversized cooling capacity limits the
infiltration of rain or runoff into the unfinished structure (for
time when dehumidification can take place); and (5) moisture
example, while roof or drainage structures are incomplete), (4)
becomes entrained on filters or intake (15, 14).
structural materials installed over wet surfaces, (5) infiltration
6.4.2.9 See Ref (16) for detailed descriptions of typical
of hot, humid air before air conditioning is operational, (6)
building moisture problems.
ineffective vapor retarder installation and/or crawl space
ventilation, and (7) insufficient waterproofing of the founda-
7. Basic Fungal Growth Assessment
tion.
6.4.2.2 Envelope-Related—Deficiencies related to construc- 7.1 The most important requirement of an assessment for
tion defects such as improperly installed or missing flashing, fungal growth is an on-site inspection of the subject building or
weep holes, membranes, and gaps in finishes, sealants or air portion of the building as per the scope of work. The
D7338 − 14 (2023)
professional performing the assessment may choose or empha- 7.3.3 Building Occupancy—Building uses should be noted.
size or minimize any of the topics below during the Review of past occupant complaints and interviews with
assessment, as the scope of the project and its quality objec- current occupants may aid in identifying temporal and spatial
tives dictate. Parts of an assessment may include: the collection patterns related to moisture and fungal growth problems
of background information, the formulation of a hypothesis or
7.4 Hypothesis Formulation and Testing—A hypothesis is a
hypotheses, an on-site inspection including moisture dynamics,
tentative assumption tested for logical or empirical consistency
an evaluation of the HVAC system, hypothesis testing, site
(17, 18). Hypotheses may involve a specific area (for example,
documentation and written report.
the cause of a discoloration) or the entire building (for
example, the efficacy of the vapor retardation system). A
7.2 Scope of Work—Before attempting an inspection or
hypothesis should consist of one simple statement. For
assessment, a detailed scope of work should be agreed upon by
example, “The tenant complains that the discoloration on a
the principals of the investigation (for example, building
wallpaper is mold that resulted from a water leak” contains two
owner, manager, lawyer, consultant, investigator). Some
statements. In this case, it would be advantageous for hypoth-
scopes may be extremely limited (for example, find the extent
esis testing to split this complaint into two hypotheses: (1) The
of the fungal growth resulting from a single event water leak),
discoloration on the wallpaper is fungal in nature, and (2) that
to virtually unlimited (for example, investigate a case of
same fungal growth was enabled by a water leak. Testing these
employee malaise). Topics to be considered before agreeing to
two hypotheses would involve different observations or actions
a scope of work include but are not limited to: (1) the
during the assessment.
buildings, building or part of a building to be assessed, (2) the
7.4.1 Formulation Before On-site Inspection—Optimally, a
nature of the problem, including complaints from occupants, if
applicable, (3) budget, (4) building use and occupation (for hypothesis should be formulated before the on-site inspection
based on the information provided while determining the scope
example, unoccupied, business, residence, ho
...