Maintenance and Technical Manual
Chapter 2
Interceptor Biological Safety Cabinet Class II A2
October 2019
2.3
Filter Loading
Over time, as the Interceptor’s filters load up, inflow velocity shown on the control
screen will begin to drop. NSF 49 recommends that motor RPM be increased when
this occurs until the control unit again shows 105 FPM.
Before considering filter replacement, the motor speed control should be adjusted
to increase the air flow. Before considering filter replacement, the fan speed and top
damper should be adjusted to increase the air flow. The Fan Speed adjustment is
located under Settings|Cabinet Setup on the Control Monitor. Select Cabinet Setup
from the menu. Fan Speed is a password protected feature. Additionally you can
adjust the top damper and increase the fan speed to attain 105 FPM inflow velocity.
Check the exhaust/downflow balance after such an adjustment is made. The steps
must be performed by an NSF Certified Technician.
Figure 2.3a
Menu Screen
Figure 2.3b
Cabinet Setup Screen
Figure 2.3c
Fan Speed Screen
Figure 2.3d
Set Normal Fan Speed
Screen
Filters should be changed when they load up to the point that further adjustment of the
motor RPM will not increase face velocity to 100 FPM. NSF accepts a range of inflow between
100-110 FPM at operating height (10" for the Interceptor).
When the static pressure difference between the negative and positive pressure
plenums reaches a certain level (generally between 1.4" and 1.8" wg depending on
BSC size and calibration), the net inflow will continue to drop over time and no further
adjustment of the motor voltage will bring the face velocity back to 105 FPM.
The Filters should be replaced at this time. An inability to maintain 100 FPM mandates
filter change-out according to NSF 49.
See Chapter 3 for Filter Replacement procedures.
