Basic Documentation

Biological Laboratories
Siemens Industry, Inc. 67
Topic Requirement(s) Commentary
Ventilation
for Biosafety
Level 4,
Cabinet
Laboratory
ASHRAE, 2011 Handbook - HVAC Applications, Laboratories, Pg. 14.16,
Containment Laboratories:
Ventilation systems for these areas will have stringent design requirements that must
be determined by the biological safety officer.
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 dedicated non-recirculating ventilation system must be provided. Only laboratories
with the same HVAC requirements (i.e., other BSL-4 labs, ABSL-4, BSL-3-Ag labs)
may share ventilation systems if gas-tight dampers and HEPA filters isolate each
individual laboratory system.
The supply and exhaust components of the ventilation system must be designed to
maintain the laboratory at negative pressure to surrounding areas and provide
differential pressure or directional airflow, as appropriate, between adjacent areas
within the laboratory.
Redundant supply fans are recommended. Redundant exhaust fans are required.
Supply and exhaust fans must be interlocked to prevent positive pressurization of the
laboratory.
The ventilation system must be monitored and alarmed to indicate malfunction or
deviation from design parameters. A visual monitoring device must be installed near
the clean change room so proper differential pressures within the laboratory may be
verified prior to entry.
Supply air to and exhaust air from the cabinet room, inner change room, and
fumigation/decontamination chambers must pass through HEPA filter(s). The air
exhaust discharge must be located away from occupied spaces and building air
intakes.
Class III BSCs must be directly and independently exhausted through two HEPA
filters in series. Supply air must be provided in such a manner that prevents positive
pressurization of the cabinet.
If Class II BSCs are needed in the cabinet laboratory, they must be installed so that
fluctuations of the room air supply and exhaust do not interfere with proper
operations. 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 the manufacturer’s recommendations. If BSC exhaust is to
be recirculated to the outside, BSCs can also be connected to the laboratory exhaust
system by either a thimble (canopy) connection or a hard ducted, direct connection
ensuring that cabinet exhaust air passes through two (2) HEPA filters—including the
HEPA in the BSC—prior to release outside. Provisions to assure proper safety
cabinet performance and air system operation must be verified.
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.