Environmental Factors:
Environmental
controls should be implemented when the risk for TB transmission
persists. Environmental controls are used to remove or inactivate
M. tuberculosis in areas in which the organism could be
transmitted. Primary environmental controls consist of controlling the
source of infection by using local exhaust ventilation (e.g., hoods,
tents, or booths) and diluting and removing contaminated air by using
general ventilation. These controls help prevent the spread and reduce
the concentration of airborne infectious droplet nuclei.
Secondary
environmental controls consist of controlling the airflow to prevent
contamination of air in areas adjacent to the source (AII rooms) and
cleaning the air (using a HEPA filter or ultraviolet germicidal
irradiation [UVGI]). To be effective, secondary environmental controls
should be used and maintained properly, and their strengths and
limitations should be recognized. The engineering design and
operational efficacy parameters for UVGI as a secondary control
measure. . Source-control techniques can prevent or reduce the spread
of infectious droplet nuclei into the air. Air-cleaning technologies
include
mechanical air filtration to reduce the concentration
of M. tuberculosis droplet nuclei and UVGI to kill or
inactivate microorganisms.
Local Exhaust Ventilation:
Aerosol-producing procedures should be performed in an area with a
type of local exhaust ventilation that captures and removes airborne
contaminants at or near their source without exposing persons in the
area to infectious agents. . Local exhaust devices typically use
hoods. Two types of hoods are used: enclosing devices, in which the
hood either partially or fully encloses the infectious source, and
exterior devices, in which the infectious source is near but outside
the hood. Fully enclosed hoods, booths, or tents are always preferable
to exterior devices because of their superior ability to prevent
contaminants from escaping. Enclosing devices should have sufficient
airflow to remove >99% of airborne particles during the
interval between the departure of one patient and the arrival of the
next. The time required to remove a given percentage of airborne
particles from an enclosed space depends on-
1)
The location of the
ventilation inlet and outlet
2)
The physical configuration of
the room or booth.
General Ventilation
General ventilation is used to-
1)
Dilute and remove
contaminated air.
2)
Control the direction of
airflow in a correctional facility setting.
3)
Control airflow patterns in
rooms. Recommended ventilation rates for correctional. facility
settings are typically expressed in ACH.
The direction of air movement relative to adjacent areas is
necessary for the containment of contaminated air. Air within a
correctional facility should flow to minimize exposure of others
within the building.
Environmental Control Maintenance:
Failure to
maintain environmental control systems properly has adversely impacted
TB control and prevention efforts at facilities throughout the United
States.
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