This page provides information on
decontaminating buildings or specific areas, systems, or items
within buildings after an actual release of anthrax. Anthrax
decontamination is a repetitive process that may involve the use of
multiple decontamination processes and technologies. Selection of
appropriate technologies varies depending on factors specific to the
release and to the technologies themselves, but the primary
considerations are always the effectiveness and safety of the
products and processes.
an area or item contaminated by anthrax involves numerous and
variable issues that are specific to individual locations. No single
technology, process, or strategy will be effective in every case.
Responders must develop a decontamination plan that takes into
account the following:
The extent of contamination and how the
contamination spread are critical considerations in isolating
affected areas and selecting appropriate decontamination
technologies. For example, if spores are widely dispersed and have
traveled through the air, decontamination may involve extensive
isolation and fumigation. In contrast, if the contamination is
limited to a small area and spores are not likely to become
airborne, then minimal isolation and surface decontamination methods
alone may suffice.
- The nature of the contamination:
including the type of anthrax involved, how it entered the
facility, and the physical characteristics that affect the
spread of contamination.
- The extent of contamination:
including the amount of contamination and possible pathways by
which it could have or will spread.
- The objectives of decontamination:
including the intended re-use of the facility and building
systems and whether items will be decontaminated for re-use or
treated for disposal.
All stakeholders--local authorities, building
owners and residents, federal, state, and local environmental and
health agencies, the affected public, and others--should be
consulted before decontamination begins. A site health and safety
plan (HASP) is needed to protect workers inside and outside the
contaminated area, as well as the surrounding population. The
facility manager should notify employees and others (such as union
representatives) of the nature and scope of the work and its
More detailed information about HASPs can be
found on the HASP page of this
results of the sampling for extent of contamination should make it
possible to distinguish between contaminated and uncontaminated
areas and to determine the types of surfaces involved. To prevent
the spread of contamination by movement of workers or equipment, it
may be advisable to isolate the contaminated area, depending on the
impacted area and the extent of contamination.
Decontamination should address the following:
|Hidden sources of contamination: Desktop computers and other objects with internal fans that draw air into the case may have filters or electrostatic devices to control dust intake.
Additional, more detailed information about
sampling for Bacillus anthracis, can be
found on the Sampling
page of this eTool.
Hidden sources of contamination: Desktop computers and other objects with internal fans
that draw air into the case may have filters or
electrostatic devices to control dust intake. These
filters or the equipment chassis may be a reservoir of
contamination. If selected technologies may damage the
item or may not penetrate to hidden locations, then these
items may be dealt with in an alternative manner. The
manufacturer of the device should be consulted if it is to
be saved for re-use.
- Pre-cleaning: Excessive amounts of
dirt or other organic material on the surface to be cleaned may
decrease the effectiveness of the selected decontamination
method. Using certain techniques, such as HEPA
vacuuming, to remove some of the dirt and debris could
reduce the need to perform more aggressive chemical
- Removal of items: To reduce
potential spread of contamination, items should be
decontaminated in place. If the selected technology will destroy
an item that must be salvaged, then the item may be removed and
decontaminated elsewhere with an alternative technology. This
requires a means of safe transport and a separate isolation
chamber, which adds complexity to the decontamination process.
technologies can be divided into three categories:
- Surface decontamination products,
which are used to treat spores on hard, non-porous surfaces such
as desks, walls, and hard flooring. There are two methods to
High Efficiency Particulate Air (HEPA)
Vacuuming: accomplishes two purposes: (1) it
helps remove dirt and other debris that may reduce the
effectiveness of subsequent decontamination, and (2) it
also removes some of the spores, reducing the number
that must be killed by subsequent decontamination. An
advantage of this technology is that there is little
potential for damage to furnishings. A limitation of
this technology is that it can only remove surface
contamination. The operator must also avoid allowing the
exhaust to stir the air in the affected room and must
safely dispose of contaminated filters.
filters can be attached to
high-volume vacuums such as this.
|Liquid Antimicrobial Products - Not for Porous Surfaces
- Liquid Antimicrobial Products - Not
for Porous Surfaces: may be used to inactivate
spores on hard surfaces only. These products--which can
be applied by pouring, mopping, or spraying--include
oxidizing, bleaching, or other agents such as aqueous
chlorine dioxide, sodium hypochlorite, hydrogen
peroxide, and peroxyacetic acid combined. Several
factors should be considered when deciding which liquid
antimicrobial products to use and how to apply them.
Each product affects surfaces differently in terms of
corrosivity, staining, and residue. These products will
be effective only if the directions for use of the
product are followed precisely (such as mixing
directions, application method and dosage rate,
pre-cleaning of surfaces, and contact time).
- Fumigation, which involves use of an
antimicrobial gas or vapor to destroy aerosolized spores and
spores adhered to non-porous and porous surfaces. In addition to
decontaminating a variety of surfaces, fumigants are able to
decontaminate airborne spores that a surface cleaner would miss.
- Other decontamination products,
which are primarily used in chambers or other specialized
equipment. Technologies that can be used to decontaminate
specific items outside the affected area or environment include
Selection of the appropriate technology will
require an evaluation of the specific site conditions and nature of
contamination. Other considerations include the conditions required
for effective application (for example, humidity for fumigations or
pH for certain surface treatments), how the technology will affect
the area or item being treated, and the risks associated with use
(such as physical, chemical, and toxicologic parameters of the
- Chemical Sterilization: chemicals
such as ethylene oxide, chlorine dioxide, or paraformaldehyde
are used to kill spores on discrete items placed in a
sterilization chamber. Sufficient aeration of the items
following treatment is necessary to remove residual amounts of
the sterilant and any toxic by-products that may have
formed. For effective decontamination, each chemical
sterilant has specified ranges of temperature, relative
humidity, concentration, and duration of application.
- Irradiation: irradiation
techniques, including cobalt-60 and electron beam
technologies, can effectively destroy anthrax. These
techniques are generally available only for off-site
decontamination. They may destroy magnetic media such as film
or videotape, and they tend to be expensive.
Environmental Protection Agency's (EPA) Technology Innovation
Office (TIO) has developed an information clearinghouse
as a centralized location to collect and disseminate information
about decontamination technologies and also for technology vendors
to provide information.
the Effectiveness of Decontamination
are separate criteria, described below, for judging the
effectiveness of decontamination of objects in an off-site
sterilization chamber, and for decontamination of sites such as
offices or buildings.
A different technology may be used for further decontaminating an
area in which sampling showed the presence of viable anthrax spores.
For example, if evidence of bacterial growth is found only on a desk
in an office that was fumigated, an approved liquid sporicidal
product may be applied to complete decontamination of the
- For objects decontaminated in an off-site sterilization
chamber, biological indicators such as surrogate spore test
strips, may be placed in the chamber along with the objects.
Although the optimal results of decontamination would be if the
biological indicators showed no evidence of bacterial growth,
OSHA believes that there may be safe alternatives to the
"no growth" decontamination.
- To determine whether decontamination of a site has been
effective, a rigorous round of environmental sampling should be
performed following the decontamination process, and the samples
should be cultured for Bacillus anthracis
in a nationally accredited lab. Rigorous environmental sampling
should be done in all decontaminated sites, regardless of type
of technology used or the extent of the decontamination. In
areas that have been fumigated, biological indicators (such as
surrogate spore strips) may be used to determine whether the
fumigant has effectively permeated the area under specific
conditions (such as concentration, time, temperature, and
relative humidity) sufficient to kill Bacillus
anthracis spores. The results of the culture of both the
environmental samples and the biological indicators should be
evaluated to determine the effectiveness of the fumigation.
Again, the optimal results of decontamination would be if the
biological indicators showed no evidence of bacterial growth.
However, OSHA believes that there may be safe alternatives to
the "no growth" decontamination.
Once an area has been determined to be effectively decontaminated,
there is no guarantee that all viable spores have been eliminated,
even when post-decontamination samples show no growth. Moreover,
statistical calculations of the effectiveness of sampling and
analytical methods indicate that some spores may remain in a
decontaminated area even though environmental sampling shows
"no growth." Nevertheless, the potential risk of a person
contracting the disease in such an area is considered to be
Although the "no growth" decontamination goal may be the
best possible way to ensure safety in re-occupying a decontaminated
area, OSHA believes that there may be safe alternatives, especially
in workplace situations where the use of PPE, special work
practices, or other engineering controls might also minimize the
risk of disease.
This approach is consistent with the NCP, which allows case-by-case
decisions based on the future use of the site and other controls
that might be used to ensure safety. Decisions on alternative
options such as these would have to be site-specific, and supported
by experts in epidemiology, public health, industrial hygiene, and
environmental protection. The basis for these types of decisions
should also be thoroughly documented.
Additional information about decontamination techniques and process,
and post-decontamination sampling strategies can be found on the Sampling
page of this eTool.