NIOSH Interim Recommendations for the Cleaning and Remediation of Flood-Contaminated HVAC Systems: A Guide for Building Owners and Managers
Introduction
During flooding, systems for heating, ventilating, and air conditioning (HVAC) can become submerged in flood waters. As a result, these systems may contain substantial amounts of dirt and debris and may also become contaminated with various types of microorganisms such as bacteria and fungi.
The following recommendations will help ensure that HVAC systems contaminated with flood water are properly cleaned and remediated to provide healthy indoor environments.
Microorganisms may grow on all surfaces of HVAC system components that
were
submerged in flood waters. In addition, moisture can collect in HVAC
system
components that were not submerged (such as air supply ducts above the
water line)
and can promote the growth of microorganisms. Therefore, all components
of the HVAC
system that were contaminated with flood water or moisture should be
thoroughly
inspected, cleaned of dirt and debris, and disinfected by a qualified
professional. The
following recommendations will help ensure that HVAC systems contaminated
with
flood water are properly cleaned and remediated to provide healthy indoor
environments.
These interim recommendations are based on current knowledge
as of
September 21, 2005; the recommendations will be updated and revised as
appropriate,
as additional information becomes available.
Steps Before Cleaning and Remediation
If the building is to remain partly occupied (for example, on upper
floors not
affected by flood waters), isolate the construction areas where HVAC
systems
will be cleaned and remediated by using temporary walls, plastic sheeting,
or
other vapor-retarding barriers. Maintain the construction areas under
negative
pressure (relative to adjacent non-construction areas) by using blowers
equipped
with HEPA filters (high-efficiency particulate air filters) to exhaust
the area.
To ensure complete isolation from the construction areas, it
may be necessary to
pressurize the adjacent non-construction areas and temporarily relocate
the
outdoor-air intake for the HVAC system serving the occupied areas.
Take precautions to protect the health of workers who are cleaning
and
remediating the HVAC system. Make sure that workers wear at least
an N-95
NIOSH-approved respirator to protect against airborne microorganisms.
Increased levels of respiratory protection (for example, powered,
air-purifying
respirators equipped with HEPA filters) may be appropriate depending
on the
level of visible contamination. In addition, when using chlorine
bleach or other
disinfectants in poorly ventilated environments, it may be necessary
to use
appropriate chemical cartridges in addition to the particulate filters
to protect
workers from breathing the chemical vapors. Employers must implement
a
complete respiratory protection program that meets the requirements
of the
OSHA respiratory protection standard (29 Code of Federal Regulations
1910.134). The minimum requirements for a respiratory protection
program
include a written standard operating procedure for the following:
selecting and
using respirators; the medical evaluation of workers to determine
whether they
are physically able to wear the respirator selected for use; training
and
instructions on respirator use; the cleaning, repair, and storage
of respirators; the
continued surveillance of work area conditions for worker exposure
and stress;
and a respirator fit-testing program. For tight-fitting respirators,
fit-testing is
necessary to help ensure that the respirator fits tightly, reducing
the potential for
leakage of outside air from around the edge of the mask. In addition,
employers
must provide workers with appropriate skin, eye, and hearing protection
for the
safe performance of their jobs.
HVAC Cleaning and Remediation
Remove all flood-contaminated insulation surrounding and within
HVAC system
components. Discard these contaminated materials appropriately
following
applicable Federal, State, and local regulations.
Remove contaminated HVAC filter media and discard appropriately
following
applicable Federal, State, and local regulations.
After removing any insulation and filters, clean all flood-contaminated
HVAC
system component surfaces with a HEPA-filtered vacuum cleaner
to remove dirt,
debris, and microorganisms. Pay special attention to filter racks,
drain pans,
bends and horizontal sections of air ducts where debris can collect.
After removing any insulation or debris, disinfect all HVAC
system component
surfaces while the HVAC system is not operating. Use a solution
of 1 cup of
household chlorine bleach in a gallon of water. Do not mix bleach
with other
cleaning products that contain ammonia.
Follow the disinfection procedure with a clean water rinse.
Depending on the
amount of debris present, it may be necessary to mechanically
clean the HVAC
system component surfaces with a steam or a high-pressure washer
before
using the disinfectant.
Note: Remove and discard HVAC system components that are
contaminated with flood water and cannot be effectively cleaned
and disinfected. Replace them with new components.
After cleaning and disinfecting or replacing the HVAC system
components,
replace the insulation – preferably with an external (i.e.
not in the air stream)
smooth-surfaced insulation to help prevent debris and microorganisms
from
collecting in the future.
Make sure that the HVAC system fan has been removed and serviced
(cleaned,
disinfected, dried thoroughly, and tested) by a qualified professional
before it is
placed back into the air-handling unit.
During the cleaning and remediation process, consider upgrading
the HVAC
system filtration to the highest efficiency filters practical
given the static pressure
constraints of the HVAC system fan. This step has been shown to
be one of the
most cost-effective ways to improve the long-term quality of the
indoor
environment, since it reduces the amount of airborne dusts and
microorganisms.
Resuming HVAC Operations
After cleaning and disinfecting or replacing HVAC system,
have a qualified
professional thoroughly evaluate its performance and correct
it as necessary
before the building is occupied again. The HVAC system performance
should
conform to the recommendations contained in ASHRAE Standard
62-2004,
Ventilation for Acceptable Indoor Air Quality.
Before the building is occupied again, operate the HVAC
system continuously in
a normal manner at a comfortable temperature for 48 to 72
hours. During this period, it may be beneficial to open the
HVAC outdoor air dampers to the
maximum setting that still allows you to provide the desired
indoor air
temperatures. If objectionable flood-related odors persist
after this “flush out”
period, reassess by looking for flood-contaminated areas that
were not identified
earlier and continue the flush-out process until odors are
no longer apparent.
Replace the HVAC filters used during the flush-out prior to
building occupancy.
After a building is occupied again, make frequent (for example,
weekly) checks of
the HVAC system to ensure that it is operating properly. During
these checks,
inspect the HVAC system filters and replace them when necessary.
Gradually
reduce the frequency of the HVAC system checks to monthly
or quarterly
inspections, depending on the routine operation and maintenance
specifications
for the HVAC system.
If no routine operation and maintenance program is in place
for the HVAC
system, develop and institute such a program. At a minimum,
include the
following routine procedures: inspection and maintenance of
HVAC components,
calibration of HVAC system controls, and testing and balancing
of the HVAC
system.
After the building is occupied again, maintain the interior
temperature and relative
humidity to conform with the ranges recommended in ASHRAE
Standard 55-
2004, Thermal Environmental Conditions for Human Occupancy.
Additional Resources
Additional information about the cleanup and restoration of water-damaged
and moldcontaminated HVAC systems is available from the Institute
of Inspection, Cleaning and Restoration Certification (IICRC)
and the National Air Duct Cleaners Association
(NADCA). Their pertinent documents (Standard and Reference Guide
for Professional
Mold Remediation [IICRC S520] and Assessment, Cleaning and Restoration
of HVAC
Systems [ACR 2005]) are available for purchase at www.iicrc.org/ and www.nadca.com/publications/, respectively. The University of Minnesota also
has a document titled, “HVAC System Decontamination” available
for free off the
internet at www.dehs.umn.edu/iaq_hsd.htm.
References
Vinken W, Roels P [1984]. Hypersensitivity pneumonitis
to Aspergillus fumigatus in
compost. Thorax 39:74-74.
Malmberg P, Rask-Andersen A, Palmgren U, Höglund
S, Kolmodin-Hedman B,
StDlenheim G [1985]. Exposure to microorganisms, febrile
and airway-obstructive symptoms, immune status, and
lung function of Swedish farmers.
Scandinavian Journal of Work and Environmental Health
11:287-293.
Topping MD, Scarsbrick DA, Luczynska CM, Clarke EC,
Seaton A [1985]. Clinical and immunological reactions
to Aspergillus niger among workers at a
biotechnology plant. British Journal of Industrial Medicine
42:312-318.
Edwards JH [1980]. Microbial and immunological investigations
and remedial action after an outbreak of humidifier
fever. British Journal of Industrial Medicine 37:55-62.
Weiss NS, Soleymani Y [1971]. Hypersensitivity lung
disease caused by
contamination of an air-conditioning system. Annals
of Allergy 29:154-156.
Hodgson MJ, Morey PR, Attfield M, Sorenson W, Fink
JN, Rhodes WW, Visvesvara GS [1985]. Pulmonary disease
associated with cafeteria flooding. Archives of Environmental
Health 40(2):96-101.
Fink JN, Banaszak EF, Thiede WH, Barboriak JJ [1971].
Interstitial pneumonitis due to hypersensitivity to
an organism contaminating a heating system. Annals of
Internal Medicine 74:80-83.
Banazak EF, Barboriak J, Fink J, Scanlon G, Schlueter
EP, Sosman A, Thiede W,
Unger G [1974]. Epidemiologic studies relating thermophilic
fungi and
hypersensitivity lung syndrome. American Review of Respiratory
Disease
110:585-591.
OSHA [1998]. Occupational Safety and Health Standards
(29 CFR 1910.134).
Occupational Safety and Health Administration, Washington,
D.C.
ASHRAE [2004]. ASHRAE Standard 62-2004: Ventilation
for Acceptable Indoor Air Quality. American Society
of Heating, Refrigerating, and Air-conditioning Engineers,
Atlanta, GA.
ASHRAE [2004]. ANSI/ASHRAE Standard 55-2004: Thermal
Environmental
Conditions for Human Occupancy. American Society for
Heating, Refrigerating,
and Air-conditioning Engineers, Atlanta, GA.
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