Biomedical Engineering Reference
In-Depth Information
not allowing visitors outside the lobby area
without an escort. Layered levels of security
access should be considered. For example,
entry to a hospital's patient care areas could
be less strict than to hospital laboratories, and
successively more strict for other areas, such
as ventilation control rooms. Physical security
is of prime concern in lobby areas.
Depending upon the design and operation
of the HVAC system and the nature of the
CBR agent release, HVAC control may not
be appropriate in all emergency situations.
Lobbies, loading docks, and mailrooms might
be provided with manually operated exhaust
systems, activated by trained personnel to
remove contaminants in the event of a known
release, exhausting air to an appropriate area.
In other instances, manipulation of the HVAC
system could minimize the spread of an agent.
If an HVAC control plan is pursued, building
personnel should be trained to recognize a
terrorist attack quickly and to know when to
initiate the control measures. For example,
emergency egress stairwells should remain
pressurized (unless they are known to contain
the CBR source). Other areas, such as labo-
ratories, clean rooms, or pressure isolation
rooms in hospitals, may need to remain venti-
lated. All procedures and training associated
with the control of the HVAC system should
be addressed in the building's emergency
response plan.
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2.
Assess filtration
. Increasing filter efficiency
is one of the few measures that can be
implemented in advance to reduce the conse-
quences of both an interior and exterior
release of a particulate CBR agent. However,
the decision to increase efficiency should
be made cautiously, with a careful under-
standing of the protective limitations resulting
from the upgrade. The filtration needs of a
building should be assessed with a view to
implementing the highest filtration efficiency
that is compatible with the installed HVAC
system and its required operating parame-
ters. In general, increased filter efficiency
will provide benefits to the indoor environ-
mental quality of the building. However, the
increased protection from CBR aerosols will
occur only if the filtration efficiency increase
applies to the particle size range and physical
state of the CBR contaminant. It is important
to note that particulate air filters are used for
biological and radiological particles and are
Ventilation and Filtration
HVAC systems and their components should be
evaluated with respect to how they impact vulner-
ability to the introduction of CBR agents. Rele-
vant issues include the HVAC system controls, the
ability of the HVAC system to purge the building,
the efficiency of installed filters, the capacity of
the system relative to potential filter upgrades,
and the significance of uncontrolled leakage into
the building. Another consideration is the vulnera-
bility of the HVAC system and components them-
selves, particularly when the facility is open to the
public. For buildings under secure access, interior
components may be considered less vulnerable,
depending upon the perceived threat and the confi-
dence in the level of security.
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1.
Evaluate HVAC control options
. Many central
HVAC systems have energy management
and control systems that can regulate airflow
and pressures within a building on an emer-
gency response basis. Some modern fire alarm
systems may also provide useful capabilities
during CBR events. In some cases, the best
response option (given sufficient warning)
might be to shut off the building's HVAC
and exhaust system(s), thus, avoiding the
introduction of a CBR agent from outside.
In other cases, interior pressure and airflow
control may prevent the spread of a CBR
agent released in the building and/or ensure
the safety of egress pathways. The decision
to install emergency HVAC control options
should be made in consultation with a qual-
ified HVAC professional that understands
the ramifications of various HVAC oper-
ating modes on building operation and safety
systems.
