Basic Documentation

Biological Laboratories
Siemens Industry, Inc. 65
Topic Requirement(s) Commentary
Ventilation
for Biosafety
Level 3
ASHRAE, 2011 Handbook - HVAC Applications, Laboratories, Pg. 14.16,
Containment Laboratories:
The ventilation system must be single pass, nonrecirculating and configures to
maintain the laboratory at negative pressure relative to surrounding areas. Audible
alarms and visual monitoring devices are recommended to notify personnel if the
laboratory pressure relationship changes from a negative to a positive condition. The
user may wish to have alarms reported to a remote constantly monitored location.
Gastight dampers are required in the supply and exhaust ductwork to allow
decontamination of the laboratory. The ductwork between these dampers and the
laboratory must also be gastight. All penetrations of the Biosafety Level 3 laboratory
envelope must be sealable for containment and to facilitate gaseous decontamination
of the work area.
U.S. Dept. of Health and Human Services, Centers for Disease Control and
Prevention publication: Biosafety in Microbiology and Biomedical Laboratories,
(BMBL) 5th edition 2009:
A BSL-3 laboratory has special engineering and design features
All procedures involving the manipulation of infectious materials must be conducted
within BSC’s or other physical containment devices.
BSC’s must be installed so that fluctuations of the room air supply and exhaust do not
interfere with proper operations. BSCs should be located away from doors, heavily
traveled laboratory areas, and other possible airflow disruptions.
A ducted air ventilation system is required. This system must provide sustained
directional airflow by drawing air into the laboratory from “clean” areas toward
“potentially contaminated” areas. The laboratory shall be designed such that under
failure conditions the airflow will not be reversed.
The laboratory exhaust air must not re-circulate to any other area of the building.
The laboratory building exhaust air should be dispersed away from occupied areas
and from building air intake locations or the exhaust air must be HEPA filtered.
HEPA filtered exhaust air from a Class II BSC can be safely re-circulated into the
laboratory environment if the cabinet is tested and certified at least annually and
operated according to manufacturer’s recommendations. BSCs can also be
connected to the laboratory exhaust system by either a thimble (canopy) connection
or directly exhausted to the outside through a hard connection. Provisions to assure
proper safety cabinet performance and air system operation must be verified. Class
III BSCs must be directly (hard) connected up through the second exhaust HEPA
filter of the cabinet. Supply air must be provided in such a manner that prevents
positive pressurization of the cabinet
Laboratory personnel must be able to verify directional airflow. A visual monitoring
device, which confirms directional airflow, must be provided at the laboratory entry.
Audible alarms should be considered to notify personnel of air flow disruption.
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The need to seal the laboratory for
decontamination sometimes adds components
such as filters and shut-off dampers to the
ventilation system. In some cases, it also
leads to a very tight room envelope, which
affects design of the pressurization system.
As a practical matter, it is helpful if the facility
operators using the Building Automation
System, get the same pressurization
information that the laboratory workers see at
the entry.