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Mold Inspection and Mold Remediation
Recommendations by Government Industrial Hygienists in their book
Bioaerosols Assessment and Control
Below are important excerpts on mold inspection and mold
remediation techniques from the book Bioaerosols Assessment and
Control published
by the American Conference of Governmental Industrial Hygienists (ACGIH),
Cincinnati, OHIO. This massive book is a must-read. Buy your copy at ACGIH
Website:
http://www.acgih.org
1. Bioaerosols are those airborne particles that are living or
originate from living organisms. Bioaersols include microorganisms (i.e.,
culturable, nonculturable, and dead microorganisms) and fragments, toxins,
and particulate waste products from all varieties of living things.
Bioaerosols are ubiquitous in nature and may be modified by human
activities. All persons are repeatedly exposed,
day after day, to a wide variety of such materials.
2. ACGIH uses the term biologically derived airborne contaminants
to describe bioaerosols, gases, and vapors that living organisms produce.
3. ACGIH has defined biological contamination in buildings as
the presence of (a) biologically derived aerosols, gases, and vapors of a
kind and concentration likely to cause disease or predispose persons to
adverse health effects, (b) inappropriate concentrations of outdoor
bioaerosols, especially in buildings designed to prevent their entry, or (c)
indoor biological growth and remnants of growth that may become airborne and
to which people may be exposed.
4. The term biological agent is used to refer to a substance
of biological origin that is capable of producing an effect, for example, an
infection or a hypersensitivity, irritant, inflammatory, or other response.
5. There are no Threshold Limit Values (TLVs) for interpreting environmental
measurements of
(a) total culturable or countable bioaerosols (e.g., total bacteria or
fungi), (b) specific culturable or countable bioaerosols (e.g., [the mold
species] Aspergillus fumigatus), (c) infectious agents (e.g.,
Legionella pneumophila), or (d) assayable biological contaminants (e.g.,
endotoxin, mycotoxins, allergens, or microbial volatile compounds).
6. Conducting a Walkthrough Investigation. During initial walkthroughs,
investigators collect primarily observational data (i.e., information
obtained by visual inspection of a building and interviews with the building
operator and occupants). Investigators (a) examine the physical structure,
maintenance activities, and occupancy patterns of a building, (b) look for
potential sources of biological agents, (c) look for evidence of current or
past water damage or excess moisture,
(d) note sources of other indoor air contaminants, and (e) as needed,
formulate plans for an in-depth investigation or for control and
remediation of noted problems.
7. Sources of biological agents may be found (a) outside buildings, (b) in
attics and below-grade spaces, (c) within wall cavities, (d) in HVAC
systems, and (e) in the occupied space.
8. Bulk Sampling. Bulk samples are portions of environmental materials
(e.g., settled dust, sections of wallboard, pieces of duct lining, carpet
segments, or return air filters) tested to determine if they may contain or
be contaminated with biological agents. Testing is done to determine if
organisms (e.g., microorganisms or dust mites) have colonized the material
and are actively growing as well as to identify surfaces where previously
airborne biological particles have deposited and accumulated.
9. It has been hypothesized that settled dust or
dust collected on return-air filters would reflect previously airborne
biological particles and provide a more representative picture of bioaerosol
exposure than short-term air samples.
10. Remediation of Microbial Contamination. Prevention of
microbial growth indoors is only possible if the factors that may allow it
are identified and controlled. When prevention has failed and visible
microbial growth has occurred in a building, restoration requires (a)
removal of porous materials showing extensive microbial growth, (b) physical
removal of surface microbial growth on non-porous materials to typical
background levels, and (c) reduction of moisture to levels that do not
support microbial growth. Preventing water intrusion during the remediation
process is advised to prevent further microbial growth. However, Foarde et
al. (1997) found that lowering indoor relative humidity triggered spore
release from fungal contamination on duct material. Therefore,
remediators should consider whether contaminated materials should be removed
before measures to thoroughly dry the environment are undertaken.
Identification of the conditions that contributed to microbial proliferation
in a building is the most important step in remediation. No effective
control strategy can be implemented without a clear understanding of the
events or building dynamics responsible for microbial growth.
11. Removing Existing Contamination. Growth that has occurred in a surface
layer of condensation on painted walls or non-porous surfaces (including
wood) can usually be removed by (a) vacuuming using equipment with
high-efficiency filters or direct air exhaust to the outdoors, (b) washing
with a dilute solution of biocide and detergent, or (c) cleaning, thorough
drying, and painting. Porous materials that have sustained extensive
microbial growth must often be removed. Examples of porous materials are
ceiling tiles, installed carpeting, upholstered furnishings, and wallboard.
Extensive microbial growth refers not only to the extent of the area
affected but also the degree to which microorganisms have degraded a
material for use as a food source. “Extensive” visible fungal growth has
been defined as surface areas greater than three square meters (32 square
feet) (New York City Dept. Of Health, 1993; Health Canada, 1995; ISIAQ,
1996). Carpeting and drapes that can be removed for thorough cleaning and
drying may be salvageable. Valuable books and papers can sometimes be
rescued by fumigation, followed by freeze-drying and vacuum removal of
residual particles.
12. The removal and cleaning of contaminated materials must not be
undertaken without proper precautions, because disturbance of contaminated
materials can result in bioaerosol release. Disturbance of microbial growth
in air-handling systems may lead to the dissemination of bioaerosols
throughout a building. Resulting exposures to biological agents may
compromise the health of remediation workers and building occupants. When
visible contamination is extensive, containment procedures similar to those
used to handle hazardous wastes (e.g., asbestos) are required to safely
remove contaminated materials. Remediators can consider using the
recommendations others have developed to handle removal of materials visible
contaminated with potentially toxigenic fungi (New York City Dept of Health,
1993; Health Canada, 1995). Recommended removal methods take into
consideration both the nature and extent of contamination, that is, the
particular microorganisms present and the amount of material or area
affected. Such work should be conducted while buildings are unoccupied.
13. In general, the removal and containment precautions required for
toxigenic fungi should be used for remediating any visible fungal
contamination because virtually all fungi can cause allergy (in sensitized
individuals), and many fungi produce toxins.
14. Critical barrier [containment wall]. Two layers of polyethylene sheeting
are used to create a critical barrier to isolate a contaminated area from
clean or occupied building zones. Critical barriers must block all openings,
fixtures, and HVAC system components to prevent the spread of dirt and
spores beyond the containment area. The barriers must be constructed without
disturbing contaminated materials.
15. Negative pressure. A negative air pressure differential between the work
area and the surrounding space must be created to prevent contaminants from
leaving the work zone. An air filtration device (e.g., a negative air
machine) with a HEPA filter should be used to negatively pressurize the work
area.
16. Decontamination unit. A decontamination unit should be constructed for
entry into and exit from a remediation area. The unit may consist of a
single or multiple chambers depending on the size of the operation. A
multiple-chamber unit typically has a work room, equipment room, and air
lock. At present there is no scientific evidence to justify the use of
showers in the decontamination system.
17. Contaminated debris. Contaminated debris should be double bagged (6 mil
polyethylene bags) and passed through the decontamination unit. The bag
surfaces are Hepa vacuumed before transport into uncontaminated parts of a
building. Bags are removed by the most direct exist route. Direct transport
of sealed bags to the outdoors is preferable (e.g., through a window r door
connected to the decontamination unit). Bagged debris can be disposed of in
a landfill as if the contents were moldy compost. Workers disposing of these
bags should be aware of their contents, take measures to avoid bag rupture,
and be trained in how to deal with such an event.
18. Containment-Unit Cleaning. A combination of HEPA vacuuming and damp
wiping (with minimum water) should be used to remove settled dust prior to
disassembly of critical barriers. Water sprays can be used to reduce dust
aerosolization but must not wet surfaces excessively. A final inspection of
a containment area should be made to ensure that all dust and visible debris
have been removed. Air sampling by spore trap or other means may also be
conducted to verify that air concentrations of fungal spores…in the
containment zone are qualitatively and quantitatively similar to ambient out
door air. Use of surface sampling (e.g., adhesive tape sampling) is
advisable to determine that only background concentrations and types of
fungi are present on porous surfaces.
19. Area cleaning. Dust that may have settled on surfaces and materials
outside a remediation enclosure should be removed by HEPA vacuuming or damp
wiping followed by thorough drying.
20. HVAC System Remediation. Applications of biocides as a substitute for
removing microbial growth and settled biological material is not considered
acceptable. In the first place, most disinfectants and sanitizers are
approved for use on previously cleaned rather than soiled surfaces.
Secondly, the allergenicity and toxicity of biological material is not
related to microorganism viability. Contaminated porous materials in HVAC
systems must be removed to the bare (underlying) metal and the contaminated
materials appropriately discarded. Full containment procedures should be
implemented when removing extensive areas of contaminated porous materials
from large HVAC system components (e.g., air handling plenums). Depending on
the extent of visible fungal contamination, removal of porous materials from
smaller HVAC system components (e.g., unit ventilators and fan-coil units)
requires source or local containment precautions supplemented by HEPA vacuum
cleaning…A few [biocide] products were previously registered with the U.S.
Environmental Protection Agency specifically for use on the inside of air
ducts (USEPA, 1997). However, these products were registered solely for the
purpose of sanitizing the smooth surfaces of unlined sheet-metal ducts. The
USEPA no longer registers biocides for specific use in HVAC systems. No
products are registered as biocides for use on glass-fiber ductboard or
glass-fiber-lined ducts. Therefore, it is important to determine if sections
of a system contain such materials before permitting the application of any
biocide.
21. Biocide use. Biocides are toxic chemicals or physical agents capable of
killing or inactivating one or more groups of microorganisms, that is,
vegetative bacteria, mycobacteria, or bacteria spores; vegetative fungi or
fungal spores; parasites; or viruses… Remediators must carefully consider
the necessity and advisability of applying biocides when cleaning
microbially contaminated surfaces. The goal of remediation programs should
be removal of all microbial growth. This generally can be accomplished by
physical removal of materials supporting active growth and thorough cleaning
of non-porous materials. Therefore, application of a biocide would serve no
purpose that could not be accomplished with a detergent or cleaning agent.
Prevention of future microbial contamination should be accomplished by (a)
avoiding the conditions that led to past contamination, (b) using materials
that are not readily susceptible to biodeterioration, and (c) where
necessary, applying compounds designed to suppress vegetative bacterial and
fungal growth or using materials treated with such compounds… Killing
microorganisms usually does not destroy their [allergenic] or toxic
properties. Therefore, even microbial growth that has been treated with a
biocide should be removed from indoor environments. Antimicrobial agents
should not be used in place of moisture control and regular cleaning and
maintenance, but antimicrobial agents may protect some materials from
microbial growth.
22. Important Biocide Classes: Alcohols (ethyl, isopropyl), Aldehydes
(formaldehyde, glutaraldehyde), Halogens (chlorine, iodine, and bromine
compounds), Hydrogen peroxide, Phenolic compounds, and Quaternary ammonium
compounds (cationic detergents).
23. Basic Precautions for Biocide Use. Never use biocides in occupied
buildings. Never spray biocides into functioning air-handling units. Ensure
that biocide applicators are trained and use personal protective gear to
prevent respiratory, mucus membrane, and dermal exposures. After treatment,
remove residual biocide and any remaining surface microbial growth.
24. Gas-Phase/Vapor-Phase Biocides. No gas- or vapor-phase biocide can
effectively and safely remediate a microbially contaminated building because
of problems with biocide delivery, efficacy, and toxicity. First and
foremost, there is no means to deliver a gas- or vapor-phase biocide to all
spaces and surfaces within a building. Microbial growth will remain viable
unless an extremely effective agent reaches every wall and ceiling space,
literally every nook and cranny.
25. Judging Remediation Effectiveness. The success of a remediation effort
is judged in part by the visible degree of contaminant removal that is
achieved. Effectiveness may also be confirmed by sampling. The ultimate
criterion for the adequacy of abatement efforts for treating biological
contamination is the ability of people to occupy or re-occupy the space
without health complaints or physical discomfort. Cessation of bioaerosol
exposure should result in a cessation of bioaerosol-related symptoms.
Likewise, mitigation of environmental conditions that led to problems of
microbial contamination should result in the absence of microbial growth as
long as the control measures continue to be effective. If this is not the
case, the investigator did not correctly identify or sufficiently address
the underlying causes of the problem. Following building restoration, the
kinds and concentrations of biological agents in air samples should be
similar to what is found locally in outdoor air. Concentrations of
biological agents in surface samples should be similar to what is founding
well-maintained buildings or on construction and finishing building
materials.
26. Porous materials. Porous materials from which microbial growth cannot be
adequately cleaned must be removed from buildings. In buildings where
extensive microbial growth has occurred, porous materials not actively
supporting microbial growth may still harbor spores and particles released
from other sources. Where appropriate, such materials should be thoroughly
cleaned by washing or HEPA vacuuming and should be monitored for residual
contamination. Over time, levels of residual contamination should fall. In
addition, if porous materials have adsorbed odors, removal of the material
may ultimately be necessary to return the building to its pre-contamination
state…Porous materials that, for any reason, remain wet for more than 24
hours should be discarded.
27. Long-Term Prevention Plans. Any remediation attempt that does not
include long-term plans to maintain systems and prevent recurrence is
short-sighted and destined to fail. There is no one-time, complete “cure” to
microbial contamination within structures. Rather, continued oversight and
attention to conditions that may allow microbial growth must become an
integral part of a control plan. Three basic strategies should be allowed to
maintain building performance and prevent microbial contamination: (a)
routine surveillance inspections and prompt response to problems, (b)
adequate preventive maintenance of the building structure as well as HVAC
and plumbing systems, and (c) adequate housekeeping, including an emphasis
on proper and routine cleaning. |
