The following fact sheet is part of a series relating to chemicals that may be used in authorized personnel according to the specific requirements of the applicable crisis exemption and
approved decontamination plans. These chemicals are not intended for use by the general public.
What is Chlorine Dioxide?
Chlorine dioxide (ClO2) is an antimicrobial pesticide recognized for its disinfectant properties since the
early 1900's. Antimicrobial pesticides are substances used to control harmful microorganisms
including bacteria, viruses or fungi on inanimate objects and surfaces. In 1967, EPA first registered
the liquid form of chlorine dioxide for use as a disinfectant and sanitizer. In 1988, EPA registered
chlorine dioxide gas as a sterilant.
Chlorine dioxide kills microorganisms by disrupting transport of nutrients across the cell wall. Chlorine
dioxide can be generated in a gas or liquid form and smells like chlorine bleach. Chlorine dioxide
should not be confused with chlorine gas. They are two distinct chemicals that react differently and
produce by-products that also have little in common.
Antimicrobial pesticides are substances used to control harmful microorganisms including bacteria,
viruses and fungi on inanimate objects and surfaces primarily in indoor environments. Types of
antimicrobial products have traditionally included sanitizers, disinfectants, and sterilants.
is a substance that significantly reduces the bacterial population in the
inanimate environment, but does not destroy or eliminate all bacteria or other
is a substance that destroys or eliminates a specific species of infectious or
other public health microorganism, but not necessarily bacterial spores, in the inanimate
is a substance that destroys or eliminates all forms of microbial life in the
inanimate environment, including all forms of vegetative bacteria, bacterial spores, fungi,
fungal spores, and viruses.
EPA's Registration of Pesticides
Before a pesticide can be marketed and used in the United States, EPA must evaluate the pesticide
to ensure that it meets federal safety standards. EPA grants a registration (or a license) for a public
health pesticide product only after the Agency has reviewed efficacy and safety data to ensure that,
when used according to the specific instructions on the label, the product is effective and does not
cause any unreasonable adverse effects on human health or the environment. Such evaluation is
particularly important for antimicrobial pesticides (sanitizers, disinfectants, and sterilants) which are
used to reduce or eliminate microbial contamination.
The pesticide label provides specific safety precautions and use directions for handling or using the
product. EPA has concluded that chlorine dioxide products registered to date have met federal
standards for environmental and human health safety.
Registered Uses for Chlorine Dioxide
Registered Liquid and Gaseous Products
EPA first registered chlorine dioxide gas as an antimicrobial pesticide in the 1980s. Chlorinedioxide gas is registered for sterilizing manufacturing and laboratory equipment,environmental surfaces, tools, and clean rooms. It is also used in pharmaceutical researchand production. Liquid chlorine dioxide formulations were first registered in the 1960's asdisinfectants and are used on a variety of sites including pets; farm animals; bottling plants;food processing, handling and storage plants; and many others.
Other Registered Uses
Chlorine dioxide gas and liquid formulations also have many other industrial uses including:
Applying Chlorine Dioxide
Pesticide products containing either sodium chlorite
or stabilized chlorine dioxide
mixed with another "reactive" chemical - usually an acid - to produce chlorine dioxide in a liquid or
gaseous state. The resulting mixture is applied within a specific sterilization or disinfection system.
The liquid chlorine dioxide is then applied to hard surfaces with a sponge or mop or as a coarse
spray. Chlorine dioxide gas is also generated on site and is released into a sealed treatment area
where it remains for several hours before being removed. After the treatment is completed, the
chlorine dioxide gas is neutralized with sodium bisulfite. The treatment may leave a fine residue, but it
is not toxic.
FIFRA Section 18 Emergency Exemptions and Anthrax
Under Section 18 of FIFRA, EPA "may exempt any federal or state agency from any provision of this
Act if the Administrator determines that emergency conditions exist which require such exemption."
Normally, a federal or state agency submits an application for a FIFRA exemption to EPA for review
and approval. If EPA approves the request, it issues either a specific or a public health exemption, as
appropriate. However, if the emergency is of such urgency that the federal or state agency does not
have enough time to submit an application for exemption and wait for EPA's approval, then the federal
or state agency may issue a crisis exemption, which is effective for 15 days. In order for the crisis
exemption to be extended beyond 15 days, the federal or state agency must submit an application for
exemption to EPA.
To handle all anthrax contamination cases as quickly as possible, the Agency has decided to issue all
crisis exemptions itself. To obtain a crisis exemption from EPA for the unregistered use of a pesticide
against anthrax, a state or federal agency must submit a written request describing the antimicrobial
product(s) to be used; how, when and where they will be used; the data demonstrating efficacy of the
product for the intended purpose; and how human health and safety will be protected. Prior to issuing
the exemption, EPA will perform a multi-disciplinary risk assessment of the requested use, relying on
data that they have supplied for the pesticide.
If, during this review, EPA notes any adverse human health or environmental concerns, EPA may
deny the exemption request. If, however, EPA believes that the proposed use of an antimicrobial
product will be effective and will protect human health and the environment, EPA will issue a crisis
exemption. Moreover, if EPA determines that use of the product is needed beyond the
15-day use period, EPA will complete an application for a public health exemption on behalf of the
requesting entity, which allows the crisis exemption to continue in effect until it is either withdrawn or
EPA issues a public health exemption.
Determination of Safety and Efficacy for Crisis Exemptions for Chlorine Dioxide
EPA has reviewed data related to safety and effectiveness before allowing an emergency exemption
for liquid and gaseous chlorine dioxide to be used specifically for anthrax decontamination. Available
published data suggest that liquid and gaseous chlorine dioxide will reduce bacterial spore
populations under specific conditions including concentration, pH, and contact time.
Based on this review, EPA issued crisis exemptions for the limited sale, distribution, and use of liquid
and gaseous chlorine dioxide against anthrax. EPA has determined that the public health threat
posed by the anthrax incidents constitutes a public health emergency of such immediacy that normal
processing and review of a conventional public health exemption under FIFRA are neither prudent nor
practical. Under the crisis exemption for liquid chlorine dioxide
, registered products (containing
sodium chlorite) may be sold or distributed only to employees of federal, state or local government
agencies, or of the U.S. Postal Service, for anthrax cleanup. Crisis exemptions for gaseous chlorine
(from certain sodium chlorite products) have been issued for use at the Hart Senate Office
Building (November 30, 2001), to decontaminate the exterior of mail packages that have been
received by U.S. government offices (February 26, 2002), and to test fumigation of lockers in a trailer
at the U.S. Postal Service Brentwood Processing and Distribution Center, Washington, D.C. (June 21,
Since issuing the initial crisis exemption on November 9, 2001, EPA tested the effectiveness of liquid
chlorine dioxide and found that it was effective on hard surfaces (500 milligrams per liter, at 30
minutes contact time), but not effective on porous surfaces (e.g.,carpeting, chairs, couches, and other
fabric surfaces) under the conditions of use specified in the Section 18 Crisis Exemption of November
9, 2001. On March 28, 2002, EPA amended the crisis exemption for liquid chlorine dioxide to limit its
use to hard surfaces only. This amendment does not affect the results of the cleanups performed with
liquid chlorine dioxide to date. At the cleanup sites where liquid chlorine dioxide was used, all porous
surfaces were pre-treated and removed for final disposal at a facility capable of destroying any
remaining spores. Liquid chlorine dioxide, along with other methods and technologies, continues to be
effective against anthrax spores on hard surfaces. Current fact sheets are available on EPA's Anthrax
Web page at: .
Emergency Use of Liquid Chlorine Dioxide in Anthrax Decontamination
Application of the pesticide products under the crisis exemption is limited to specific buildings or
treatment sites identified by EPA or other federal, state, or local governmental authorities, or the
United States Postal Service. Applications must be conducted according to use instructions from
federal, state, or local emergency response personnel following a plan that includes the following
Pre-sampling to determine the extent of spore contamination at specific locations.
Spot remediation of highly contaminated surfaces through HEPA filter vacuuming.
Gross surface decontamination with liquid chlorine dioxide.
Post-treatment sampling to determine that the anthrax decontamination has been
Re-treatment with liquid chlorine dioxide if viable spores are detected.
These steps apply to facilities where the treated surfaces will be reused or the facility will be re-occupied. These steps do not necessarily apply to wastes or debris intended for disposal in anappropriate facility.
Applying Liquid Chlorine Dioxide
On March 28, 2002, the Crisis Exemption for liquid chlorine dioxide was amended to specify its use to
decontaminate hard surfaces only
. Applications must be conducted according to use instructions
from federal, state, or local emergency response personnel following a plan that includes the following
Pre-sampling to determine the extent of spore contamination at specific locations.
Spot remediation of highly contaminated surfaces through HEPA filter vacuuming.
Gross surface decontamination using a liquid solution of chlorine dioxide under the
a rate of 500 mg/L liquid chlorine dioxide will be applied;
applications will be made at room temperature (68 degrees F, 20 degrees C);
treatments will have a contact time of at least 30 minutes.
Post-treatment, environmental sampling to determine whether viable anthrax spores
Re-treating with liquid chlorine dioxide if viable spores are detected.
Post-treatment testing to determine that the anthrax decontamination has been effective.
Any remaining liquid chlorine dioxide must be removed from the treated areas of the building beforepeople are allowed to re-enter. After treatment, experts must determine - through post-treatmentsampling - that the treatment was effective before anyone is allowed back into the building.
Applying Gaseous Chlorine Dioxide
Based on review of available data, EPA believes that gaseous chlorine dioxide can be used in a
facility decontamination procedure that includes sampling, cleaning, treating, and re-sampling,
followed by additional treatment if necessary. The crisis exemptions for gaseous chlorine dioxide
issued for the Hart Senate Office building (November 28, 2001) and for the exterior of mail packages
(February 26, 2002) involved products containing sodium chlorite as the active ingredient to generate
gaseous chlorine dioxide on site, followed by post-treatment environmental sampling to confirm that
the treated areas were free from anthrax spores ( i.e., showing no growth when samples are cultured
in the laboratory). The conditions of application are described below. These conditions did not
necessarily apply to personal protective equipment and other debris that were further treated offsite.
Conditions of application:
A minimum concentration 500-550 ppm chlorine dioxide gas was initially applied for aminimum of 12 hours, for a minimum total of 6,000 ppm-hours. Later, the concentrationwas increased to 750 ppm for a total of 9,000 ppm-hours.
Applications were made at a minimum temperature of 70 degrees F; and
Relative humidity was maintained at a minimum of 65%. On June 17, 2002, EPA issueda crisis exemption for the U.S. Postal Service to test gaseous chlorine dioxide fumigationof lockers in a truck trailer located at the Brentwood Processing and Distribution Centerin Washington, D.C. The lockers in the test were not contaminated with Bacillus anthracis
Rather, they were set up to simulate the 3,000+ lockers inside the building that would
to be fumigated either together with the building or separately. The purpose of the test
to help determine the ClO2 concentration and contact time would be necessary to obtain asuccessful decontamination of employees' lockers.
More Information on Antimicrobial Pesticides
If you have general questions about the federal pesticide program browse the Web site, or contactEPA's pesticides office:
Tel: 703-305-5017Fax: 703-305-5558E-mail:
Anthrax is an acute infectious disease caused by the
spore-forming bacterium Bacillus anthracis
. Anthrax most
commonly occurs in farm animals, but it can also infect
humans. Symptoms of disease vary, but usually occur
within 7 days after exposure. The serious forms of human
anthrax are inhalation (a respiratory infection), cutaneous (a skin infection), and intestinal anthrax.
Anthrax contamination was detected in U. S. Senate
office buildings and at several other locations across the
United States. The EPA has been working closely with
the Capitol Hill Police, the U.S. Postal Service, the
Centers for Disease Control, the FBI, and other agencies
to ensure that existing anthrax contamination is quickly
identified and thoroughly cleaned up, and also to prevent
While anthrax cleanup is a new challenge, EPA and its
partners have assembled an effective toolbox for tackling
it. In a very short time, we've significantly advanced the
science and technology of detecting and cleaning up
EPA's Role in Responding to Anthrax Contamination
EPA provides technical expertise and oversight in detecting anthrax contamination and ensuring that
cleanup fully protects public health and the environment.
Local police, health department officials or hazardous materials teams are usually the first ones on
scene in response to incidents that could involve anthrax. They do the initial sampling, and if anthrax
is found, more comprehensive sampling is needed to fully assess the severity and extent of
Private building owners are responsible for hiring qualified contractors to conduct this sampling and
perform whatever decontamination is necessary. Due to the extreme hazards potentially
associated with exposure to anthrax, it is absolutely essential to work closely with EPA and
other federal agencies with expertise in sampling, decontamination and protection of workers.
EPA is notified through the to
ensure that work proceeds appropriately. Under the to take over this work if the situation exceeds the capabilities of the owner or state and local
Once the extent of contamination is assessed, EPA provides technical expertise in developing a site-
specific cleanup plan. Decontamination of anthrax is a rapidly evolving field, with new technologies
continually being advanced and tested. It is EPA's responsibility to ensure that antimicrobial
pesticides used in anthrax decontamination plans meet all Federal requirements for standards of
safety and effectiveness. In developing a strategy for decontamination, EPA consults with a variety of
scientific experts, such as:
• EPA's Environmental Response Team Scientific Support Coordinators• EPA research laboratories• the National Institute of Occupational Safety and Health• the Centers for Disease Control and Prevention• the US Army Medical Research Institute for Infectious Diseases• the Defense Advanced Research Projects Agency
State and local environmental and health officials are also consulted, and we may requestrecommendations from national experts in universities and private industry.
The cleanup plan reflects the size and type of the potentially contaminated areas (e.g., a large openmailroom or a small office cubicle), how the contamination was delivered (e.g., highly concentratedspores contained in an envelope or tracked down the hallway from a contaminated area), howcontamination could be dispersed (e.g., through an air handling system or by ordinary movementwithin an office) and other characteristics related to daily activities in the area. Since each site isdifferent, each cleanup plan will be tailored to the unique situation at that site.
Once cleanup is completed, a new round of sampling is done to make sure that the anthrax sporeshave been removed or killed, and that it is safe to reoccupy the area. In some cases, it may benecessary to use more than one type of treatment or to treat more than one time.
The National Response System
EPA's response to recent anthrax incidents is part of a larger National Response System that has
effectively dealt with a wide range of environmental emergencies for almost 30 years. It is a multi-
layered system of individuals and teams from local, state, and federal agencies, industry, and other
organizations that share expertise and resources to ensure that oil spill control and cleanup activities
are timely and efficient, and that they minimize threats to human health and the environment.
New Methods and Technologies
Anthrax decontamination is a rapidly evolving field, with new methods and technologies continually
being developed and tested. Several different antimicrobial pesticides and devices are being currently
used by qualified experts under carefully controlled conditions in anthrax cleanups being done across
EPA's Technology Innovation Office is leading an effort to collect and disseminate information abouttechnologies that detect and kill anthrax and other biological agents. is a clearinghouse for information about these technologies and their vendors, and links toother resources pertaining to the detection and decontamination of biological agents. We are alsooperating a vendor helpline at (703) 390-0701 and an email address at tofield inquiries from vendors of detection, decontamination, and measurement technologies.
Under the Federal Insecticide, Fungicide, and Rodenticide Act, all products that claim to be asanitizer, disinfectant, sterilant, or sporicde need a registration number or approval for emergency usefrom the Antimicrobials Division of EPA's Office of Pesticide Programs. Vendors of decontaminationtechnologies who wish to get their technology registered or approved for emergency use shouldcontact Jeff Kempter in EPA's Office of Pesticide Programs, Antimicrobials Division, at (703)305-5448, or . For a complete list of crisis exemptions issued by EPA forpesticide products used for decontamination of anthrax see ().
Other Counter-terrorism Activities
Like many other federal agencies, EPA is working closely with the to
develop a national strategy to strengthen protections against terrorist threats or attacks in the United
States. But EPA has also been actively involved in federal counter-terrorism planning and response
efforts for the past several years. See EPA's for
more information. Our primary responsibilities have been to help state and local response personnel
plan for emergencies, to provide counter-terrorism response training, and to provide technical
expertise and other resources in the event of a terrorist incident.
What You Should Do
Anthrax Fact Sheets
Frequently Asked Questions
As part of a Unified Command effort, EPA responded to anthrax contamination discovered in
Congressional buildings in the Capitol Complex. EPA emergency responders have taken thousands
of samples in more than 30 buildings to determine whether anthrax was actually present and to
design and carry out site-specific cleanup strategies where contamination was found. Senator
Daschle's office suite was fumigated with chlorine dioxide gas on December 1, (see ) and on Dec. 30, further fumigation was done in the air handling
system that serves that area. Several other suites and common areas in the Hart Building and in other
buildings in the Capitol Complex were cleaned using chlorine dioxide liquid, foams and high efficiency
particle air (HEPA) filter vacuuming. Post cleanup sampling showed no remaining viable anthrax, and
on Jan. 22, the Hart, Ford and Longworth Buildings were cleared for reoccupancy.
Related activities include:
• sampling to confirm and determine the extent of contamination• evaluating sampling results• isolating areas to prevent spread of contamination• removing critical objects for special decontamination procedures• working with the US Postal Service and other agencies to evaluate the effectiveness of
potential disinfectants and cleanup technologies
• cleaning up localized areas of decontamination
In addition to the work in the Capitol Complex, EPA is supporting numerous other agencies in themetropolitan Washington area in identifying and eliminating anthrax contamination. EPA is providingextensive assistance to the US Postal Service in designing and carrying out comprehensive cleanupplans for contamination at their Brentwood facility.
EPA conducted extensive sampling at the American Media, Inc. building in Boca Raton. We are now
providing technical assistance to the owner in developing and carrying out a strategy for
decontaminating the building.
EPA also provided technical assistance to the US Postal Service in sampling and decontaminating
five postal facilities in Boca Raton, Lake Worth, and West Palm Beach. Decontamination has been
completed at all of these facilities.
EPA has provided technical assistance for sampling and decontamination at the Morgan US postal
facility, NBC News Headquarters, the offices of the New York Post, and the office of Mayor Giuliani.
EPA has also provided technical assistance at:
• 7 US postal facilities in New Jersey• 1 private facility in Indiana• 1 private facility in Missouri• 1 US postal facility in North Carolina• 1 US postal facility in Connecticut
Note: Due to the extreme hazards potentially associated with exposure to anthrax, it is absolutely
essential for responders to work closely with EPA and other federal agencies with expertise in
sampling, decontamination, and protection of workers.
Personal Protective Equipment
• Use of Ciprofloxacin or Doxycycline for Postexposure Prophylaxis for Prevention of
Options for Decontamination(Note: These options are authorized for use only under specific conditions tailored to thecharacteristics of each site.)
For Employers/Building Managers:
• • • • Occupational Exposure to Anthrax• •
For Technology Vendors:
EPA's Technology Innovation Office is leading an effort to collect and disseminate information about
technologies that detect and kill anthrax and other biological agents. is a clearinghouse for information about these technologies and their vendors, and links to
other resources pertaining to the detection and decontamination of biological agents. We are also
operating a vendor helpline at (703) 390-0701 and an email address at to
field inquiries from vendors of detection, decontamination, and measurement technologies.
Under the Federal Insecticide, Fungicide, and Rodenticide Act, all products that claim to be asanitizer, disinfectant, sterilant, or sporicde need a registration number or approval for emergency usefrom the Antimicrobials Division of EPA's Office of Pesticide Programs. Vendors of decontaminationtechnologies who wish to get their technology registered or approved for emergency use shouldcontact Jeff Kempter in EPA's Office of Pesticide Programs, Antimicrobials Division, at (703)305-5448, or . For a complete list of crisis exemptions issued by EPA forpesticide products used for decontamination of anthrax see (
TITLE XI: BUSINESS REGULATIONS 110. RETAIL PERMITS CHAPTER 110: RETAIL PERMITS 110.01 Limitation on sale of pharmaceuticals SELL. Furnish, give away, exchange, transfer, deliver, surrender, distribute or supply, whether or not for monetary gain or other WHOLESALER. One whose business is § 110.01 LIMITATION ON SALE OF the selling of goods in gross to retail stores fo
Quick Start Install Guide for pfSense. At the end of this guide you will be able to set up the Open Source (free) firewall pfSense. You will be able to have a seperate WiFi LAN subnet with access to the internet that cannot access the internal LAN which is seperated with firewall rules. This guide is intended for users who are from the Linksys, Netgear, D-link etc. firewall/router backgr