SterilGARD VBM-600 Baker Company Biological Safety Hood

The Sterilgard is a unique Class II Type A (N.S.F. definition, Class II, Type B3 if vented to the outside) containment cabinet fabricated of stainless steel and other materials and designed by The Baker Company, Inc.. Clean (HEPA filtered) air descends through the work zone and at the approximate center of the work area splits, exiting either through the front air intake or rear exhaust grille. It is then pulled up the surrounding negative pressure plenum, through the fan, which pushes it into the small positive pressure plenum at the top of the unit (Figure 1). Here approximately 30 % is exhausted through the top exhaust filter and approximately 70 % is recirculated through the supply filter into the work zone. A metal diffuser just below the supply filter creates a faster air flow at the front (100 - 130 LFPM) and rear (70 - 90 LFPM) of the work zone with a slower air flow (50 - 70 LFPM) over the center of the work surface. This, Baker feels, will better protect the operator and experiment by creating a more impenetrable barrier at the unit front.

Since the cabinet must get make up air to replace that air eliminated through the exhaust filter, the same volume of room air enters the system through the 8" front access opening at 100- 110 FPM. This air, which never enters the work zone, completes the air barrier at the face of the unit and is partially responsible for the containment properties of this cabinet. Because room air enters through the intake grille at the unit front, work in the unit must be performed only in the depressed area of the solid work surface.

What makes the Sterilgard unique is that the contaminated positive pressure areas are surrounded by a NEGATIVE PRESSURE PLENUM. Any particle in this zone will necessarily be drawn through the blower and trapped on a filter. This affords an extra measure of protection, as do the Edgegard suction slots at the corners of the front access opening. These slots eliminate any "skin effects" which may cause particulate entry into or egress from the cabinet at this critical point.