Chapter 3
Respirable Mass Sampling with the Cyclone
The 10-mm Nylon Dorr-Oliver Cyclone included with your aerosol monitor
can be used to discriminate between the respirable fraction and other
portions of the ambient aerosol. Four micrometers (µm) is internationally
accepted as the 50 percent cut-off size for respirable aerosol mass. Particles
larger than 4 µm impact onto the surfaces of the upper respiratory tract and
cannot reach the lungs. The cyclone accessory provided with the D
USTTRAK
monitor is designed to provide a cut-off at 4 µm. This is specified as a 50
percent cut-off at 4 µm.
The cyclone works by forcing the particle-laden air sample to swirl inside
the cyclone body. Larger (higher mass) particles cannot follow the air stream
and become trapped, while smaller particles stay in the air stream and pass
through. When using the cyclone, you can assume that all particles smaller
than the cut-off size pass through and all larger particles become trapped in
the grit pot.
The cut-off size for any cyclone is dependent on flow rate. It is very
important that the sample flow rate through the D
USTTRAK monitor be
set at 1.7 liters per minute (L/min). If some other flow rate is set, the
cut-off size will not be at 4 µm.
Using the Cyclone
To use the cyclone, be sure that you have the black inlet nozzle in place and
that the blue impactor plate is removed from the inlet. Then you must adjust
the sample flow rate to 1.7 L/min. See Chapter 4: “Maintenance
,” for details.
After the flow rate is properly set, attach it to the D
USTTRAK monitor inlet port
using the section of plastic tubing supplied with the cyclone. Slide the cyclone
body into the holder provided on the back of the D
USTTRAK monitor. See
Figure 3–2.
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