Basic Documentation

Siemens Industry, Inc. Page 7 of 10
Document No. 149-997
To leave the laboratory suite, a worker first enters
the wa
shroom and proceeds to the de-gowning
room where they remove their outer protective
garments and place them into a container for
disposal or sanitizing as appropriate. Then, they
must disinfect any personal items that were with
them inside of a laboratory room (eye-glasses,
hearing aids, etc.) Finally, depending upon the
individual circumstances and individual laboratory
practices, they may need to shower before
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proceeding to their locker room to obtain their
regular outer clothing and other personal items. Exit
is then through the normal entry and exit double
door arrangement.
Ventilation Requirements for
BSL-3 Laboratories
Figure 4 shows a diagram of a ventilation system
arrangement for a BSL-3 laboratory room.
Ventilation Airflow
The room supply air in Figure 4 consists of 100%
outside air and the airflow quantity and final
discharge temperature is controlled at the ROOM
SUPPLY AIR TERMINAL. The air is gently diffused
into the room by one or more perforated ceiling
diffusers. Room supply air should always be gently
dispersed into the room at the entry area to establish
airflow from the room entry area towards the higher
risk area without creating high velocity air currents. It
is important not to have undesirable high velocity
cross currents at the biological safety cabinets or
fume hoods.
Biosafety cabinet exhaust is connected to the
laboratory exhaust system by hard duct connections
as required for B1 or B2 Biosafety cabinets.
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A
continual amount of room air is also exhausted from
the ceiling as well as near the floor level to remove
9. A full and complete body shower is normally required when
animals are present due to the increased likelihood of
airborne pathogens that could adhere to the exposed skin or
hair of the workers.
10. If type A biosafety cabinets are used they are not required to
be hard ducted to the exhaust system but may return a
portion of their HEPA filtered exhaust into the room. Such
biosafety cabinets usually use a thimble connection that only
allows the exhaust system to remove a portion of the cabinet
exhaust.
chemical fumes that are lighter or heavier than the
room air.
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Room Ventilation Rate
BSL-3 room ventilation rates should be 4 to 8 air
changes per hour (ACH).
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The higher rate applies
during occupied periods and 4 ACH is acceptable
when the room is unoccupied. Animal holding rooms
within laboratory suites require a constant 15 ACH.
Room Pressurization
The ventilation system must establish a reliable
airflow through the suite in the direction of in
increasing contamination. This means the laboratory
room should be maintained at a negative pressure;
typically -0.10 Inch WC (-25 Pa) or more below non-
laboratory areas of the facility.
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A greater negative
pressure may be utilized to ensure the airflow
direction is always into the area of greatest risk
especially when various support facilities (incubation
rooms, autoclave rooms, etc.) are a part of the
laboratory suite. BSL-3 laboratory room air handling
system ductwork should be designed to withstand
the pressure levels resulting from any anticipated
mode of operation or failure. For example, if the
supply system fails or is shut down while the exhaust
system remains operational, the pressure in the
supply and exhaust ducts may reach the full suction
capability of the exhaust fans. Supply systems
should be designed so that supply dampers fail open
if the exhaust systems remain operating to minimize
the negative impact on the laboratory.
Figure 5 shows differential pressure relationships
betwe
en the laboratory suite rooms as well as the
area outside of the laboratory suite. Three different
negative pressure levels are utilized in this example.
The areas of highest risk such as the Laboratory
Rooms and the Autoclave Room are the most
negative as indicated by three negative signs (- - -).
Support rooms and rooms used for normal entry and
exit procedures are maintained at a lesser negative
pressure level indicated by two negative signs (- - ).
11. Some chemical fumes associated with biological laboratories
are heavier than air and therefore a floor level room exhaust
provision is sometimes recommended.
12. This is the NFPA 45 recommendation. However, specific
requirements may call for different ACH rates or not allow
reduction of the ACH rate during unoccupied periods.
13. The 0.10 Inch WC value is based on double door entry
system with a reliable pressure difference of 0.05 Inches WC
across each door. If there are more pressurized boundaries,
the lab room pressure is likely to be even more negative.