4: Performance Features and Safety Precautions
27
Motor/Blower
The motor/blower assembly pulls room air into the front of the cabinet, and re-
circulates it internally. During its recirculation, the air is split into two separate
streams. One path leads through the exhaust HEPA filter and out of the unit. The
second path flows through the supply HEPA filter, which then flows down through
the work area, as shown in Figure 4-4. The motor in the cabinet is an electronically
commutated motor (ECM). The ECM is a brushless DC motor that includes its own
power supply to convert the incoming alternating current to direct current, as well
as its own microprocessor to control and measure the motor’s operation. The
motor
utilizes Labconco’s exclusive Constant Airflow Profile
TM
(CAP) program to
deliver a consistent volume of air, throughout the life of the cabinet.
Airflow Sensor
An airflow sensor, located above the Exhaust HEPA filter, constantly monitors the
flow of exhaust air out of the cabinet. If the exhaust falls below a safe level, the
control board turns off the cabinet blower, and sounds an audible and visual alarm.
This prevents the escape of hazardous material from the front of the cabinet, in the
event of an exhaust system failure. The airflow sensor reading is shown on the
display as Inflow in feet per minute (FPM) or meters per second (M/S).
Figure 4-4
