Guidance
for Filtration and Air-Cleaning Systems to Protect Building Environments
from Airborne Chemical, Biological, or Radiological Attacks
April, 2003
DHHS (NIOSH) Pub No. 2003-136
This
document provides preventive measures that building owners and managers can implement to protect building air environments from a terrorist release of chemical, biological, or radiological contaminants.
This document
includes information about:
Filtration and Air-Cleaning Principles
Specific
recommendations
Economic Considerations
This
document is also available in PDF format 2003-136.pdf
78 pages, 801kb
Table 1. Comparison of ASHRAE Standards 52.1 and 52.2 Table 2. Mechanisms of agent vapor filtration by ASZM-TEDA carbon Table 3. Application of activated carbon impregnates
Figures
Figure 1. Common air contaminants and their relative sizes Figure 2. Scanning electron microscope image of a polyester-glass fiber filter Figure 3. Four primary filter collection mechanisms Figure 4. Fractional collection efficiency versus particle diameter for a mechanical filter Figure 5. ASHRAE Standard 52.2 test data for a MERV 9 filter showing how collection efficiency increases as the filter loads Figure 6. Scanning electron microscope image of activated carbon pores Figure 7. Comparison of collection efficiency and particle size for different filters Figure 8. Relationship among total cost, filter life, and power requirements Figure 9. Effect of face velocity on the collection efficiency and the most penetrating particle size Figure 10. Breakthrough curves for cyanogen chloride at various filter bed depths
Foreword
The Occupational Safety and Health Act of 1970 [Public Law 91-596] assures so far as possible every working man and woman in the Nation safe and healthful working conditions. The Act charges the National Institute for Occupational Safety and Health (NIOSH) with conducting research and making science-based recommendations to prevent work-related illness, injury, disability, and death.
On October 8, 2001, the President of the United States established by executive order the Office of Homeland Security (OHS), which is mandated “to develop and coordinate the implementation of a comprehensive national strategy to secure the United States from terrorist threats or attacks.” In January 2002, the OHS formed the Interagency Workgroup on Building Air Protection under the Medical and Public Health Preparedness Policy Coordinating Committee of the OHS. The workgroup included representatives from agencies throughout the Federal Government, including NIOSH, which is part of the Department of Health and Human Services, Centers for Disease Control and Prevention. In May 2002, NIOSH, in cooperation with this workgroup, published Guidance for Protecting Building Environments from Airborne Chemical, Biological, and Radiological Attacks. This document provided building owners, managers, and maintenance personnel with recommendations to protect public, private, and government buildings from chemical, biological, or radiological attacks.
With U.S. workers and workplaces facing potential hazards associated with chemical, biological, or radiological terrorism, the occupational health and safety dimension of homeland security is increasingly evident. As with most workplace hazards, preventive steps can reduce the likelihood and mitigate the impact of terrorist threats. This publication is the second NIOSH Guidance document aimed at protecting workplaces from these new threats. It provides detailed, comprehensive information on selecting and using filtration and air-cleaning systems in an efficient and cost-effective manner. Filtration systems can play a major role in protecting both buildings and their occupants.
Prevention is the cornerstone of public and occupational health. This document provides preventive measures that building owners and managers can implement to protect building air environments from a terrorist release of chemical, biological, or radiological contaminants. These recommendations, focusing on filtration and air cleaning, are part of the process to develop more comprehensive guidance. Working with partners in the public and private sectors, NIOSH will continue to build on this effort.
John Howard, M.D.
Director
National Institute for Occupational Safety and Health
Abbreviations
µm
micrometer or micron, one-millionth of a meter
AC
hydrogen cyanide; a blood agent*
ACGIH
American Conference of Governmental Industrial Hygienists
ARI
Air-Conditioning and Refrigeration Institute
ASHRAE
American Society of Heating, Refrigerating,and Air-Conditioning
Engineers
ASTM
American Society for Testing and Materials
ASZM-TEDA
U.S. military carbon: copper-silver-zinc-molybdenum triethylenediamine
BZ
3-quinuclidinyl benzilate; an incapacitating agent*
°C
degrees Celsius
CBR
chemical, biological, or radiological
CDC
Centers for Disease Control and Prevention
CFC
chlorinated fluorocarbons
CFR
Code of Federal Regulations
Cfm
cubic feet per minute
CG
phosgene; a choking agent*
CIF
chemically impregnated fibers
CK
cyanogen chloride; a blood agent*
DARPA
Defense Advanced Research Projects Agency
EPA
Environmental Protection Agency
Fpm
feet per minute
ft2
square feet
GB
isopropyl methylphosphonofluoridate; a nerve agent (sarin)*
HAZMAT
hazardous materials
HD
bis-(2-chloroethyl) sulfide; (mustard gas)*
HEPA
high-efficiency particulate air
HVAC
heating, ventilating, and air-conditioning
IEST
Institute of Environmental Sciences and Technology
km/hr
kilometers per hour
kW-h
kilowatt?hours
in
inch
LSD
d-lysergic acid diethyl amide; an incapacitating agent
m/s
meters per second
m2
square meters
m2/g
square meters per gram
m3/min
cubic meters per minute
MERV
minimum efficiency reporting value
Mm
millimeters
Mph
miles per hour
MPPS
most penetrating particle size
N95
95% efficient respirator filter for use in a non-oil mist environment
NAFA
National Air Filtration Association
NFPA`
National Fire Protection Association
NBC
nuclear, biological, and chemical
NIOSH
National Institute for Occupational Safety and Health
Nm
nanometers, one-billionth of a meter
OHS
White House Office of Homeland Security
OPT
optical microscope
OSHA
Occupational Safety and Health Administration
Pa
pascals
PCC
Policy Coordinating Committee
PPE
personal protective equipment
Ppm
parts per million
PSE
particle size efficiency
SA
arsine; a blood agent*
SEM
scanning electron microscope
TIC
toxic industrial complex
TIM
toxic industrial materiall
VX
O-ethyl-S-(2-diisopropyl aminoethyl) methyl phosphonothiolate;
a nerve agent*
yr
year(s)
*Military designation
Definitions
Aerosols:
Solid and liquid airborne particles, typically ranging in size from 0.001 to 100 µm.
air cleaning:
Removal of gases or vapors from the air.
air filtration:
Removal of aerosol contaminants from the air.
airborne contaminants:
Gases, vapors, or aerosols
arrestance:
Ability of a filter to capture a mass fraction of coarse test dust.
bioaerosol:
A suspension of particles of biological origin.
breakthrough concentration:
Saturation point of downstream contaminant buildup, which prevents the collection ability of sorbent to protect against gases and vapors.
breakthrough time:
Elapsed time between the initial contact of the toxic agent at a reported challenge concentration on the upstream surface of the sorbent bed and the breakthrough concentration on the downstream side.
challenge concentration:
Airborne concentration of the hazardous agent entering the sorbent.
channeling:
Air passing through portions of the sorbent bed that offer low airflow resistance due to non-uniform packing, irregular particle sizes, etc.
chemisorption:
Sorbent capture mechanism dependent on chemically active medium (involves electron transfer).
collection efficiency:
Fraction of entering particles that are retained by the filter (based on particle count or mass).
composite efficiency value:
Descriptive rating value for a clean filter to incrementally load different particle sizes.
critical bed depth:
See: mass transfer zone.
diffusion:
Particle colliding with a fiber due to random (Brownian) motion.
dust spot efficiency:
Measurement of a filter’s ability to remove large particles (the staining portion of atmospheric dust).
dust holding capacity:
Measurement of the total amount of dust a filter is able to hold during a dust-loading test.
electrostatic attraction:
Small particles attracted to fibers, and after being contacted, retained there by a weak electrostatic force.
electrostatic filter:
A filter that uses electrostatically enhanced fibers to attract and retain particles.
filter bypass:
Airflow around a filter or through an unintended path.
filter face velocity:
Air stream velocity just prior to entering the filter.
filter performance:
A description of a filter’s collection efficiency, pressure drop, and dust-holding capacity over time.
gas:
Formless fluids which tend to occupy an entire space uniformly at ordinary temperatures.
Particle colliding with a fiber due to particle inertia.
interception:
Particle colliding with a fiber due to particle size.
large particle:
Particles greater than 1 micrometer in diameter.
life-cycle cost:
Sum of all filter costs from initial investment to disposal and replacement, including energy and maintenance costs.
mass transfer zone:
Adsorbent bed depth required to reduce the chemical vapor challenge to the breakthrough concentration.
mechanical filter collection mechanism:
Governs particulate air filter performance.
packing density:
Ratio of fiber volume to total filter volume.
particulate filter:
Collects aerosols only—mechanically or electrostatically.
fibrous:
Assembly of fibers randomly laid perpendicular to airflow.
high-efficiency:
Primarily used to collect particles <1 micrometer.
low-efficiency:
Primarily used to collect particles >1 micrometer.
mechanical:
Cotton, fiberglass, polyester, polypropylene, or numerous other fiber materials that collect particles.
polarized:
Contains electrostatically enhanced fibers. particulate filter design: Flat-panel filter, pleated filter, pocket filter, renewable filter (see Particulate Air Filtration).
particle size efficiency:
Descriptive value of filter performance loading based upon specific particle sizes.
personal protective equipment (PPE)
Devices worn by workers to protect against environmental hazards (i.e. respirators, gloves, hearing protection, etc.).
physicochemical properties:
Physical and chemical characteristics of sorbents (pore size, shape, surface area, affinities, etc.). Characteristics of sorbent medium, e.g., pore size, shape, surface area, etc.
pressure drop:
The difference in static pressure measured at two locations in a ventilation system. A measure of airflow resistance through a filter.
release of CBR agent:
Airborne chemical, biological, or radiological release.
residence time:
Length of time that a hazardous agent spends in contact with the sorbent.
sorbent:
Porous medium that collects gases and vapors only.
vapor:
The gaseous form of substances that are normally solid or liquid at ambient temperatures.
vapor pressure:
Partial pressure of a liquid’s vapor required to maintain the vapor in equilibrium with the condensed liquid or solid.
Acknowledgments
This document was produced by the National Institute for Occupational Safety and Health (NIOSH) in cooperation with the White House Office of Homeland Security (OHS), Interagency Workgroup on Building Air Protection. The Interagency Workgroup on Building Air Protection was formed under the Medical and Public Health Preparedness Policy Coordinating Committee (PCC) of the OHS to focus on building air protection issues associated with an airborne chemical, biological, or radiological (CBR) attack. Workgroup participants provided guidance and direction at various times during this document’s development. A list of the workgroup members is given in Appendix A. This document was written by a group of Federal Government employees under the direction of CDR G. Scott Earnest, Ph.D., P.E., C.S.P. and CDR Michael G. Gressel, Ph.D., C.S.P. Contributing authors to the document and their agency affiliations are listed below.
National Institute for Occupational Safety and Health
CDR G. Scott Earnest, Ph.D., P.E., C.S.P.
CDR Michael G. Gressel, Ph.D., C.S.P.
CAPT R. Leroy Mickelsen, M.S., P.E.
Ernest S. Moyer, Ph.D.
CAPT Laurence D. Reed, M.S.
Department of the Army
Chris J. Karwacki
Robert W. Morrison
David E. Tevault, Ph.D.
Lawrence Berkeley National Laboratory
Woody Delp, Ph.D.
National Institute of Standards and Technology
Andrew K. Persily, Ph.D.
The contributions of Patrick F. Spahn of the U.S. Department of State and Joseph E. Fernback and CAPT William G. Lotz of NIOSH are also gratefully acknowledged. Anne Votaw, Pauline Elliott, Anne Stirnkorb, and Dick Carlson of NIOSH provided editorial support, produced the camera-ready copy, and prepared the graphics. Review and preparation for printing were performed by Penny Arthur.
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