Basic Documentation

Table Of Contents
Laboratory Ventilation Codes and Standards
Siemens Industry, Inc. 86
Term Definition Commentary
Biological
Safety
Cabinets and
Classifications
(Continued)
Class II Type B1 and Type B2 cabinets rely on the building exhaust system to pull
the air from the cabinet’s workspace and through the exhaust HEPA filters.
Because containment in this type of cabinet depends on the building’s exhaust
system, the exhaust fan(s) should have redundant backups.
Class III Cabinets
The Class III cabinet is a gastight, negative pressure containment system that
physically separates the agent from the worker. These cabinets provide the highest
degree of personnel protection. Work is performed through arm-length rubber
gloves attached to a sealed front panel. Room air is drawn into the cabinet through
HEPA filters. The American glovebox Society (AGS 2007) indicates that Class III
cabinets should be maintained at 0.5 in. of water below ambient pressure. Exhaust
flow rate should provide a minimum of 100 fpm inward containment velocity through
a glove port opening in the event of a glove being inadvertently removed. HEPA
filtration or incineration before discharge to the atmosphere removes or destroys
particulate material entrained in the exhaust air.
Class III systems can contain highly infectious materials and radioactive
contaminants. Although there are operational inconveniences with these cabinets,
they are the equipment of choice when a high degree of personnel protection is
required. Note that explosions have occurred in Class III cabinets used for research
involving volatile substances
Biosafety
Cabinet
Applications
(See Types of Biological Laboratories & Required Type of Biosafety Cabinet – A
Summation of Applicable Code & Standards Requirements on the following page)
The following table provides a
comprehensive listing of biological
laboratory levels, anticipated hazard, and
suitable biological safety cabinets along with
the appropriate biosafety cabinet exhaust
arrangements. This table is a summation of
the descriptions and requirements of all
standards that cover biological laboratories
and biosafety containment devices.